0/1 1streaming.ictp.it/preprints/p/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ "...

32

Upload: others

Post on 01-Apr-2021

3 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

������������������ ������������������������ ��!����"�#��$%��&('��(&�� �����%)*��+(,.-0/�1�1 2�354.6878789:48;

<>=�?A@�B(CEDGFH@�?JI.=�KML�CON�P�FH@�?JI.="FHQSR�P�?JB�=T@�?VU"PWFH=�C 3 N�QA@�N�X�FHQZY>X�[TFH=�?A\%FH@�?JI.=FH=�C

2 =]@�B�X�="FH@�?JI.="FHQ_^`@�I.ab?JPcLS=�B�X�[8dE^>[:B�=�P�de5f>Lg^>h`iG<jRkR�^ml0^mn 2 Dme5L�oMDm^Se 2 YmD>^ml 3 L�Dme5oMLqprYmose5fmLtYmoMLue 2v3 ^mlxw�fMyzR 2v3 R

{G|u}E~0�c����c�k�b�c{>�j�z��{z~�������{G��~�{�~_��|������z�E}E~�{c~��b����}��k��c����|�����c{G�E��}���{>��~�}��E����{>���t}��s{m��~ �(���c¡¢�£�����s{G��~���b��~

¤b¥ ¦�¥O¦§IH¨vP�?JB(P�©�I�ª«K�¬�?®­¯�°�±�²®³�²®´O²¶µz·�¸G¹�·.ºJµ�»�´�ºV¼.½j¾t¿TÀH±�³ »�±�Ár¾5·.ºÂ³Ã±�¿�ÄM»�¼:ÅTµ�ÆWÀÇ·v¸GÈÉ»�³Êµ�°�»�µ�±�Á

È"Æ�·.ºÂ´O»�¿O·.ËZ±�Ì%³Êµ Í:·EÎ�Ï�Á�Ð:ÑHÒ�ÎOÏ�Ó�¾5·%Ô(°�¼.Õ�Ár¾5·8ºV¼.°ÉÅHÁ

¤b¥ Ö×¥�e0X�B�@�?ÃFH¬:I%د�°�±�²®³�²®´O²¶µz·�¸G¹�·.ºJµ�»�´�ºV¼.½j¾t¿TÀH±�³ »�±�Ár¾5·.ºÂ³Ã±�¿�ÄM»�¼:ÅTµ�ÆWÀÇ·v¸GÈÉ»�³Êµ�°�»�µ�±�Á

È"Æ�·.ºÙ´�»�¿�·8ËZ±�Ì%³Êµ Í:·EÎOÏ(Á�Ð:ÑHÒvÎ�Ï�Ó�¾5·%Ô�°É¼.Õ�Ár¾5·.ºA¼.°�ż.°ÉÅ

ÚÛ¿OµGÄjÜ�Å.´]±jÈɼ.ºA¼.Æݯ�°"²¶µ�½�°�¼:²®³®·.°É¼.ºuÞ�µ�°"²®½�µu¸�·.½�ÚÛ¿�µ�·.½�µ�²®³®»�¼.º�¾t¿]À±�³®»�±�ÁmÚ�½�³Êµ�±�²¶µ�Ár¯�²Ê¼.ºÙÀ

FH=�C

nߥ�¤MI%ª�FHQA?A¬¯�°�±�²®³�²®´O²¶µz·�¸G¹�·.ºJµ�»�´�ºV¼.½j¾t¿TÀH±�³ »�±�Ár¾5·.ºÂ³Ã±�¿�ÄM»�¼:ÅTµ�ÆWÀÇ·v¸GÈÉ»�³Êµ�°�»�µ�±�Á

È"Æ�·.ºÂ´O»�¿O·.ËZ±�Ì%³Êµ Í:·EÎ�Ï�Á�Ð:ÑHÒ�ÎOÏ�Ó�¾5·%Ô(°�¼.Õ�Ár¾5·8ºV¼.°ÉÅTà

n 2 oM^mn�^>o>Lâá�e5o 2 LtR�e5Lp�B�ã�X�N"FHX�d 6878789

­«¬�ª5ª>ä>a�FH=0¥ åÉI.\(="FH=0¥ å�Q

Page 2: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

}������������

R]dOK�@�B�a�KcI ta�I�C�B�Q�å�QÃFH=�="FHX��_=�I.=��¶P(I.=TØ:B����Û©"FHX�C��Êã�I�COd�� a�I.QJB(P�N�QJB(K��0I tU�Ø:B��� I.QJCxFH=�C§K�B�Ø:B�=��� ®I.QJC§K�d]a��a�B�@�X�dxF���B(KzFHX�B�K�@�N�CO?JB(CxãTd P(I.=�K�@�FH=]@zå�X�B(K�K�N�X�B�n�I.=]@�B 3 FHX�QJI�K�?AazN�QÃFH@�?JI.=�K�ª5?A@�©xØ8FHX�?ÃFHã�QJB�K�©"FHå�B�I 5@�©�Bå�B�X�?JI]CO?JP�ãÉI���¥Çe`©�B�a�I.QJB(P�N�QJB(K��_X�B� B�X�X�B(Câ@�I�F.Kzå�B�=T@�FHa�B�X�K���©�B�å�@�FHa�B�X�K���FHX�B�P(I.abå�I8K�B(CxI 5U�Ø:B �®K�B�Ø:B�=!�?JC�B�=T@�?JP�FHQt©"FHX�C§CO?JK�P(K"�#��FH@�I.a�K���ª5?A@�©âP(B�=]@�B�X�K$ I.X�ab?A=�[EX�B�[8N�QÃFHXzå�B�=T@�FH[:I.=�K%��©�B�å�@�FH[:I.=�K��jI 5K�?JC�B(KcB�&]N"FHQ�@�I@�©�BzCO?JK�PzCO?ÃFHa�B�@�B�X�¥Me`©�BWB�QÃF.K�@�?JP�P(I.abå�QA?ÃFH=�P(B(KmI uC�B� B(P�@"�� ®X�B(B�K�I.QA?JC�å�©"F.K�B(KGFHX�BzP(I.abå�N�@�B(C�ãTd�FH="FHQAdOK�?JKmI K�@�X�FH?A=('�N�P�@�N"FH@�?JI.=�K�FH=�Cb@�©�B`X�B� B�X�B�=�P(B)�®B�&TN�?AQA?Aã�X�?AN�a*��K�@�FH@�B`?JK�C�B�@�B�X�ab?A=�B(C�ª5?A@�©�?A=�@�©�B«K�FHa�B`X�N�=�?A=bª5©�?JP�©@�©�BcB�QÃF.K�@�?JPcå�X�I.åÉB�X�@�?JB(KmFHX�BcP(I.abå�N�@�B(C�¥to>B(K�N�QA@�K«I.ã�@�FH?A=�B(C�ãTdÇN�K�?A=�[bå�K�B�N�C�I�ÊX�FH=�C�I.a =TN�a�ãÉB�X>[:B�=�B�X�FH@�I.X�Kã"F.K�B(C�I.= @�©�Bz?JC�B�F�å�X�I.å�I8K�B(C�ãTd�fmI.QA?ÃFH=§FH=�C�P(I�ʪ�I.X�¬:B�X�K(+ hG¥Élu¥�fmI.QA?ÃFH= B�@GFHQÊ¥,��wS©]d�K%¥mo>B�ØÉ¥mL.-0/1�32�4 7:;�"2�5�567�98ZFHX�Bz?A=E[:I�I]C�FH[8X�B(B�a�B�=]@>ª5?A@�©�@�©�BcX�B(K�N�QA@�KM[:B�=�B�X�FH@�B(CEã]dEimo>^>Dmi:6<;O¥ 2 @«?JKMK�©�I�ª5=�@�©"FH@mK�?A=�[8N�QÃFHXã�B�©"F(Ø�?JI.XmI �@�©�B�B�QÃF.K�@�?JP�P(I.=�K�@�FH=T@�Km=�B�FHXmP�QJI8K�Bcå"F.P�¬�?A=�[Ç?JKM?A= FH[8X�B(B�a�B�=T@Gª5?A@�©�@�©�B= ®X�B(BcØ:I.QAN�a�B×FHå�å�X�I��O?>�a�FH@�?JI.=1?�@�©�BWP(I]B�@�P�?JB�=]@�KjI u@�©�BWQJB�F.CO?A=�[�K�?A=�[8N�QÃFHX�?A@�?JB(KcFHX�B�B(K�@�?Aa�FH@�B(C�¥je`©�BWK�?AazN�QÃFH@�?JI.=�KGå�X�I�Ø:BW@�©"FH@G@�©�B©�?A[8©�B(K�@�C�B�=�K�?A@¶d K�@�X�N�P�@�N�X�B(K�I G©�B�å�@�FHa�B�X�KA��?A=�ª5©�?JP�©�@�©�BÇa�I.QJB(P�N�QJB(KkP�FH=�=�I.@�X�I.@�FH@�B���FHX�BEFHN��OB�@�?JP���?Ê¥ B8¥K�©�I%ª =�B�[TFH@�?AØ:BzwrI.?JK�K�I.=EX�FH@�?JI8K%¥

6

Page 3: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

����������� ��������� �

fGFHX�C��¶P(I.X�B�K�dOK�@�B�a�Kj©"F(Ø:B�ãÉB(B�=âB���@�B�=�K�?AØ:B�QAd K�@�N�CO?JB(C§?A=§@�©�B�QA?A@�B�X�FH@�N�X�B�@�I�a�I]C�B�QuØ.FHX�?JI.N�K�K�@�X�N�P�@�N�X�B(KI `a�FH@�@�B�X�+,2�á 9 6 8¶¥be`©�B×?A=T@�B�X�B(K�@z?A= @�©�B�K�dOK�@�B�a�KjP(I.a�B(K ®X�I.a£@�©�B F.P�@j@�©"FH@c@�©�B�d P�FH= X�B�å�X�I�CON�P(B�K�©�I.X�@X�FH=�[:B`a�I.QJB(P�N�QÃFHXuP(I.X�X�B�QÃFH@�?JI.=�K�FH=�CWB���P�QAN�C�B(CbØ:I.QAN�a�B5B���B(P�@�K�¥re`©�B`©"FHX�C��¶P(I.X�B«K�dOK�@�B�a�K�FHX�B5FHQJK�IcFH@�@�X�F.P�@�?AØ:B ®X�I.a�@�©�B�åÉI.?A=]@mI �Ø�?JB�ªsI �@�©�B= �N�=�C�FHa�B�=]@�FHQrX�B�&]N�?AX�B�a�B�=T@�KjI �@�©�Bz@�©�B�X�a�I]COd�="FHab?JP(KjK�?A=�P(B��0 ®I.XmI.ãTØ�?JI.N�KX�B�F.K�I.=�K��0@�©�B�d�P�FH=�=�I.@zP(I.QAQÃFHå�K�B�FH@zFH=]d�å�X�B(K�K�N�X�B8¥ 2 @j?JKGªtI.X�@�©x@�IÇF.C�C @�©"FH@j@�©�B ®X�B(BbB�=�B�X�[8d I �K�dOK�@�B�a�K?A=T@�B�X�F.P�@�?A=�[×@�©�X�I.N�[8©�å�N�X�B�QAdb©"FHX�C�å�I.@�B�=T@�?ÃFHQJK��]?A=OU�=�?A@�BMª5©�B�=kI�Ø:B�X�QÃFHå�K�I]P(P�N�X`FH=�C�\�B�X�IcI.@�©�B�X�ª5?JK�B��< ®N�X�@�©�B�XX�B� B�X�X�B(Cx@�I F.K�¿�¼.½�Å.ÒvÜ�·%Å.À�K�d�K�@�B�a�K��Û?JKWX�B(CON�P(B(Cß@�I�@�©�B�å�X�I�CON�P�@WI «@�©�Bk@�B�abå�B�X�FH@�N�X�B�FH=�Cx@�©�BkB�=T@�X�I.å]d:¥� 2 @>?JKGK�I�ãÉB(P�FHN�K�B×FHQAQSF(Ø8FH?AQÃFHã�QJBbP(I.=OU�[8N�X�FH@�?JI.=�Kj©"F�Ø:B�@�©�B×K�FHa�B���N�K�N"FHQAQAd�F.K�K�N�a�B(C�@�I�ãÉB�\�B�X�I���åÉI.@�B�=]@�?ÃFHQB�=�B�X�[8d:¥ � 2 =EP(I.=�K�B�&]N�B�=�P(B��O@�©�BjP(I.abå�QJB�@�BcB�&TN"FH@�?JI.=�I rK�@�FH@�BjI r@�©�BG©"FHX�C��ÊãÉI�COdkK�d�K�@�B�a�K5P�FH=�ã�BGI.ã�@�FH?A=�B(C ®X�I.a�FbK�?A=�[8QJBG?JK�I.@�©�B�X�aE¥

^>QA@�©�I.N�[8©k@�©�Bma�I8K�@`P(I.aba�I.=�FHå�å�QA?JP�FH@�?JI.=EI _@�©�B>©"FHX�C��Êã�I]COdkK�d�K�@�B�a�K�P(I.=�P(B�X�=�K`@�©�Bm@�©�B(I.X�dkI 1'�N�?JC�K��@�©�B�d�P�FH= FHQJK�I�å�QÃF(dE@�©�BWX�I.QJBWI �Ø:B�X�d�K�?Aabå�QJB ��å�N�X�B�QAdE[:B(I.a�B�@�X�?JP��Ma�I]C�B�QJKGI tK�I.QA?JC�K�¥ 2 =�å"FHX�@�?JP�N�QÃFHX���@�©�B�da�F(dW©�B�QAåb@�ImN�=�C�B�X�K�@�FH=�Cb@�©�B`?A=�'�N�B�=�P(B5I É@�©�B`a�I.QJB(P�N�QÃFHXuK�©"FHå�B�I.=b@�©�B5B�QÃF.K�@�?JPtå�X�I.å�B�X�@�?JB(K�I 3�®B���@�X�B�a�B�QAd �FH=�©"FHX�a�I.=�?JP«K�I.QA?JC�K%¥riGB�@�B�X�ab?A="FH@�?JI.=kI ÉB�QÃF.K�@�?JP`å�X�I.å�B�X�@�?JB(K�I �©"FHX�C��ÊãÉI�COd�K�I.QA?JC�K�?JK��.©�I�ª�B�Ø:B�X���Fm=�I.=��Ê@�X�?AØ�?ÃFHQ@�F.K�¬�ãÉB(P�FHN�K�BbI t=�I.=�� FH="FHQAd�@�?JP�P�©"FHX�F.P�@�B�XWI t@�©�B�?AXc?A=]@�B�X�F.P�@�?JI.=�K�¥ 2 = @�©�B×å"F.K�@���@�©�B�B�QÃF.K�@�?JP×å�X�I.åÉB�X�@�?JB(K�I ©"FHX�C��Êã�I]COd�K�I.QA?JC�K�dOK�@�B�a�Ku©"F�Ø:BMã�B(B�=�C�B�@�B�X�ab?A=�B(C* I.Xm»�·8°��Hµ��mã�I]CO?JB(K�I.=�QAd�� I.Xu©"FHX�C�K�å�©�B�X�B(K + 9�� á<6�6�89�� I.X©"FHX�C×CO?JK�P(K + 6 � á �87 89�:FH=�C I.X_©"FHX�CbB�QAQA?Aå�K�I.?JC�K + � 2�8¶¥SR]?A=�P(B`a�I8K�@SI "X�B�FHQOa�I.QJB(P�N�QJB(KuFHX�B�=�B�?A@�©�B�XSK�å�©�B�X�?JP�FHQ�=�I.XB�QAQA?Aå�K�I.?JC�FHQ �_P�FHQJP�N�QÃFH@�?JI.=�KcI `B�QÃF.K�@�?JP�å�X�I.å�B�X�@�?JB(KcI `I.@�©�B�XzK�dOK�@�B�a�KGP(I.=�K�?JK�@�B(C I `FH=�?JK�I.@�X�I.å�?JPb©"FHX�C ãÉI�CO?JB(KFHX�BcI Z?A=T@�B�X�B(K�@�¥ 2 =�å"FHX�@�?JP�N�QÃFHX���K�@�N�CO?JB(K«I SK�dOK�@�B�a�K«P(I.=T@�FH?A=�?A=�[�a�I]C�B�QÛa�I.QJB(P�N�QJB(KMI S=�I.=��¶P(I.=TØ:B���K�©"FHå�B(K��ª5©�?JP�©�CO?���B�X &]N"FHQA?A@�FH@�?AØ:B�QAd( ®X�I.aÝP(I.=]Ø:B���I.=�B(K��]a�F(d�X�B�Ø:B�FHQ�=�B�ª�å�X�I.åÉB�X�@�?JB(K5FH=�C 4 I.X�å�©�B�=�I.a�B�="F���K�I.a�BmI ª5©�?JP�©�a�F(d�U�=�C�å�X�F.P�@�?JP�FHQrFHå�å�QA?JP�FH@�?JI.=�K%¥

e`©�Bkå�QÃFH=�="FHXb©"FHX�C P�d�P�QA?JPkå�B�=T@�FHa�B�X�FH=�Cß@�©�Bkå�QÃFH=�="FHXb©"FHX�C P�d�P�QA?JPk©�B�å�@�FHa�B�X �®K�B(BÇpr?A[�¥,2����3 ®N�X�@�©�B�XX�B� B�X�X�B(C�@�I�F.K«@�©�BcåÉB�=]@�FHa�B�XmFH=�CE@�©�Bc©�B�å�@�FHa�B�X���FHX�Bc=�I.=��¶P(I.=]Ø:B�� ��K�@�FHX"�¶K�©"FHå�B(C +,2�589��©"FHX�C��Êã�I�COdka�I�C�B�Qa�I.QJB(P�N�QJB(K×I � �� ®I.QJCßFH=�C ; �� I.QJC§K�d�aba�B�@�X�dxF��OB(K��_X�B(K�å�B(P�@�?AØ:B�QAd:¥�e`©�B(K�B�FHX�B�@�©�B�QJI�ª�B(K�@×K�d]aba�B�@�X�dxF���B(K I.X�ã�?JC�C�B�=W?A=×å�B�X�?JI]CO?JP�P�X�dOK�@�FHQAQA?A=�B�å�©"F.K�B(K�¥re`©�B(I.X�B�@�?JP�FHQ"FH=�CWB��Oå�B�X�?Aa�B�=T@�FHQ�K�@�N�CO?JB(KZI "@�©�BtåÉB�=]@�FHa�B�X�K + �86 á�:; 8�FH=�C�@�©�B«©�B�å�@�FHa�B�X�K + ��� � �:; � � ;�8�K�©�I�ª�B(C�@�©"FH@�Ø8FHX�?JI.N�KtK�I.QA?JC�å�©"F.K�B(KuP�FH=ÇB��O?JK�@�?A=�@�©�B(K�BMK�dOK�@�B�a�K�¥ ��¦§BF(Ø:I.?JCkN�K�?A=�[×@�©�B>ªtI.X�CÇP�X�dOK�@�FHQ�?A=�@�©�BmP(I.=T@�B��O@5I Ûå�QÃFH=�="FHX5K�d�K�@�B�a�Ktã�B(P�FHN�K�BmI Û@�©�B>ªtB�QAQ�¬]=�I%ª5=Çå�X�I.ã�QJB�a�Kª5?A@�© @�©�B�@�X�FH=�K�QÃFH@�?JI.="FHQcI.X�C�B�Xk?A=�@¶ª�I CO?Aa�B�=�K�?JI.=�K + � 5�� 4 7 8¶¥ ��R�I.a�B�@�©�B�X�a�I]COd�="FHab?JP§FH=�C�K�@�X�N�P�@�N�X�FHQå�X�I.å�B�X�@�?JB(KtI �@�©�B(K�B5å�©"F.K�B(K�©"F(Ø:B>ã�B(B�=�C�B�@�B�X�ab?A=�B(C�ã]d�n�I.=]@�B 3 FHX�QJI�K�?AazN�QÃFH@�?JI.=�K:+ �89 á � ;8¶¥ 2 =�å"FHX�@�?JP�N�QÃFHX��å�X�B�QA?Aab?A="FHX�dqK�@�N�CO?JB(K�I jK�I.a�BEC�B�=�K�B�K�@�X�N�P�@�N�X�B(K�I G@�©�B�©�B�å�@�FHa�B�X�K�©"F�Ø:BE?A=�CO?JP�FH@�B(C @�©"FH@�@�©�B�d B��O©�?Aã�?A@FH=�I.a�FHQJI.N�K ��=�B�[TFH@�?AØ:B��«w_I.?JK�K�I.=�X�FH@�?JI8K=+ ��� � � ;�8¶¥

e`©�B�w_I.?JK�K�I.= X�FH@�?JI������5?JK�F�&]N"FH=T@�?A@¶d P�©"FHX�F.P�@�B�X�?A\(?A=�[gC�B� ®I.X�a�FH@�?JI.=�K�I �B�QÃF.K�@�?JP�a�B(CO?ÃFO¥ 2 @ÇP�FH= ãÉBC�B�@�B�X�ab?A=�B(C�ãTd�?A=]@�X�I]CON�P�?A=�[EFH=�?A=OU�=�?A@�B(K�?Aa�FHQrP�©"FH=�[:BWI S@�©�B�K�@�X�B(K�KGFHQJI.=�[kF�P(B�X�@�FH?A= CO?AX�B(P�@�?JI.= ��ª5©�B�X�B�F.KI.@�©�B�X«P(I.abå�I.=�B�=T@�KMI _@�©�BjK�@�X�B(K�K`@�B�=�K�I.X«FHX�BG¬:B�å�@`U���B(C0�tFH=�CÇa�B�F.K�N�X�?A=�[b@�©�BjK�@�X�FH?A=�FHQJI.=�[b@�©�?JK5CO?AX�B(P�@�?JI.=FH=�C�FGCO?AX�B(P�@�?JI.=�å�B�X�å�B�=�CO?JP�N�QÃFHX�@�Ij?A@�¥��W?JK�C�B�U�=�B(C�F.KS@�©�B`=�B�[TFH@�?AØ:BMX�FH@�?JIjI É@�©�B«@�X�FH=�K�Ø:B�X�K�B5K�@�X�FH?A=�P�©"FH=�[:B

9

Page 4: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

@�I×@�©�BjQJI.=�[8?A@�N�CO?A="FHQrK�@�X�FH?A=�P�©"FH=�[:BWFH=�C���?A=�[:B�=�B�X�FHQ ��?A@«C�B�å�B�=�C�KMI.=�ã�I.@�©E@�©�BjCO?AX�B(P�@�?JI.=�K�¥e`©�B�wrI.?JK�K�I.=ßX�FH@�?JI8KzI 5@¶d�å�?JP�FHQ�a�FH@�B�X�?ÃFHQJKWFHX�B�=�I.=��Ê=�B�[TFH@�?AØ:B��Z?Ê¥ B8¥�@�©�B�a�FH@�B�X�?ÃFHQJK�P(I.=]@�X�F.P�@��®B��Oå"FH=�C0�

@�X�FH=�K�Ø:B�X�K�B�QAd ª5©�B�= å�N�QAQJB(C ��å�N�K�©�B(C0�WQJI.=�[8?A@�N�CO?A="FHQAQAd:¥ 2 @bK�©�I.N�QJC ã�B�K�@�X�B(K�K�B(C��u©�I�ª�B�Ø:B�X��`@�©"FH@�=�B�[TFH@�?AØ:BwrI.?JK�K�I.=ÇX�FH@�?JIz?JK5FHQAQJI%ªtB(CÇãTd�@�©�B>K�@�FHã�?AQA?A@ d�P(I.=�CO?A@�?JI.=�K5B�Ø:B�=Ç?A=�@�©�BmP�F.K�BmI 0?JK�I.@�X�I.å�?JPGK�dOK�@�B�a�K + 4�2�8¶¥Sn�I.X�B��I�Ø:B�X��_K�dOK�@�B�a�KGI t=�B�[TFH@�?AØ:B�wrI.?JK�K�I.= X�FH@�?JIEFHX�B×=�I.@`¨vN�K�@G@�©�B(I.X�B�@�?JP�FHQuP�N�X�?JI8K�?A@�?JB(K + 4 6 �14 9 8Sã�N�@cP�FH= ©"F(Ø:B�FQJI.@MI Z?A=T@�B�X�B(K�@�?A=�[ÇFHå�å�QA?JP�FH@�?JI.=�K�¥�R]N�P�©�K�dOK�@�B�a�K5©"F�Ø:BjãÉB(B�=�a�FH=TN� ÊF.P�@�N�X�B(CEa�I.X�Bj@�©"FH=�F�C�B(P�F.C�BzFH[:I + 46 8FH=�CÇK�?A=�P(Bm@�©"FH@`@�?Aa�B>@�©�B�d�©"F(Ø:BGã�B(B�=�F�K�N�ãO¨�B(P�@5I ÛØ:B�X�d�?A=T@�B�=�K�?AØ:BjK�@�N�CO?JB(K$+ 4 � á�5�58¶¥uR]dOK�@�B�a�K`I Û=�B�[TFH@�?AØ:BwrI.?JK�K�I.=bX�FH@�?JIm©"F(Ø:B`ã�B(B�=bP(I.?A=�B(CE¼.´ �]µ�²®³®»�±_ãTdWLSØ8FH=�K + ; 6 8¶¥_p�I.XuFH=�?JK�I.@�X�I.å�?JP5K�d�K�@�B�a�KrK�©�I�ª5?A=�[j@�©�B�=�B�[TFH@�?AØ:BwrI.?JK�K�I.=EX�FH@�?JIb?A=�P(B�X�@�FH?A=�CO?AX�B(P�@�?JI.=�KMI.=�QAd ��@�©�Bc="FHa�B�¼ �.³ ¼.º_¼.´��Tµ�²®³ »�±`©"F.K«ã�B(B�=�?A=T@�X�I�CON�P(B(C + ;�58¶¥

e`©�B�a�FH?A= FH?Aa I j@�©�?JK�å"FHå�B�X�?JKb@�IâC�B�@�B�X�ab?A=�B�B�QÃF.K�@�?JP�å�X�I.åÉB�X�@�?JB(KkI j@�©�B�C�B� B(P�@"�� �X�B(B��5C�B�=�K�BEK�I.QA?JCK�@�X�N�P�@�N�X�B(K�I Gå�B�=T@�FHa�B�X�K�FH=�C ©�B�å�@�FHa�B�X�K ��?Ê¥ B8¥ ?A=�FHã�K�B�=�P(B�I GØ.F.P�FH=�P�?JB(K��tCO?JK�QJI�P�FH@�?JI.=�K��tCO?JK�P�QA?A="FH@�?JI.=�K��B�@�P8¥ �zãTdbFHå�å�QAd]?A=�[j@�©�BMK�@�X�FH?A=���'�N�P�@�N"FH@�?JI.=�a�B�@�©�I�C + 6 � � �:; ��2 787 á!2 789 8�FH=�C×@�IG@�B(K�@S@�©�B5P(I.=TØ:B�X�[:B�=�P(BMI É@�©�?JKa�B�@�©�I�C I.X>B�QÃF.K�@�?JP�FHQAQAd�FH=�?JK�I.@�X�I.å�?JPzå�©"F.K�B(K�¥Me`©�Bzå�X�B(K�B�=T@jK�@�N�COd�X�B(K�I.QAØ:B(K>@�©�B�å�X�I.ã�QJB�a I tFHN���B�@�?JP�?A@¶d�I @�©�B`a�I8K�@SC�B�=�K�B`K�@�X�N�P�@�N�X�B(K�I É@�©�B�©�B�å�@�FHa�B�X�K�¥ 2 @SB��O@�B�=�C�K�FHQJK�Im@�©�B«FHa�I.N�=T@�I �F(Ø8FH?AQÃFHã�QJB«C�FH@�FGP(I.=�P(B�X�=�?A=�[K�dOK�@�B�a�KSP(I.=�K�?JK�@�B(CbI 0FH=�?JK�I.@�X�I.å�?JP5a�I�C�B�Q�a�I.QJB(P�N�QJB(Ku?A=T@�B�X�F.P�@�?A=�[z@�©�X�I.N�[8©�©�?A[8©�QAd×FH=�©"FHX�a�I.=�?JPMåÉI.@�B�=]@�?ÃFHQJK�¥R]N�P�©�C�FH@�F�FHX�BjN�K�B� ®N�Q�@�I�P(I.=�K�@�X�N�P�@«Ø8FHX�?JI.N�K5@�©�B(I.X�B�@�?JP�FHQZFHå�å�X�I��O?Aa�FH@�?JI.=�KGFH=�CÇ@�I�@�B(K�@5@�©�B�aE¥

e`©�B�K�@�X�N�P�@�N�X�B�I `@�©�B�å"FHåÉB�Xc?JK�F.K$ I.QAQJI�ª«K�¥ 2 =âR�B(P8¥ 2�2 K�I.a�Bbã"F.K�?JP ÊF.P�@�KzP(I.=�P(B�X�=�?A=�[�@�©�B�B�QÃF.K�@�?JP�?A@¶d@�©�B(I.X�dßFHX�BkX�B(P�FHQAQJB(CqFH=�Cß@�©�BÇK�?AazN�QÃFH@�?JI.=�a�B�@�©�I]Cß?JKWå�X�B(K�B�=T@�B(C�¥ 2 =�R�B(P8¥ 2�2�2 ªtBÇã�X�?JB�'�dâC�B(K�P�X�?AãÉBk@�©�BC�B�=�K�B«K�@�X�N�P�@�N�X�B(KuI �@�©�B5åÉB�=]@�FHa�B�X�K�FH=�C�©�B�å�@�FHa�B�X�K�ª5©�?JP�©kB�QÃF.K�@�?JP5å�X�I.å�B�X�@�?JB(KtFHX�B«K�@�N�CO?JB(C�?A=b@�©�B5å�X�B(K�B�=]@å"FHå�B�X�¥ 2 = R�B(P8¥ 2 Ö @�©�B×I.ã�@�FH?A=�B(C X�B(K�N�QA@�KmP(I.=�P(B�X�=�?A=�[�@�©�BWB�QÃF.K�@�?JP×å�X�I.åÉB�X�@�?JB(KjI �@�©�BWK�@�N�CO?JB(C K�@�X�N�P�@�N�X�B(KFHX�BbCO?JK�P�N�K�K�B(C FH=�C P(I.abå"FHX�B(C ª5?A@�© @�©�B ®X�B(BWØ:I.QAN�a�B×@�©�B(I.X�d:¥�e`©�B×QÃF.K�@GK�B(P�@�?JI.=§P(I.=T@�FH?A=�Kj@�©�BbK�N�aba�FHX�dFH=�CEP(I.=�P�QAN�K�?JI.=�K%¥

� ��� ����������� ��� � � � ��� ��� �

ÖuFHX�?JI.N�K×a�B�@�©�I�C�Kb©"F(Ø:BÇã�B(B�= å�X�I.åÉI8K�B(Cß?A= @�©�BkQA?A@�B�X�FH@�N�X�B� I.XWK�?AazN�QÃFH@�?JI.=�K�I mB�QÃF.K�@�?JPÇå�X�I.åÉB�X�@�?JB(K�I a�I�C�B�Q0K�d�K�@�B�a�K$+ 9 ;�� 9 5���6 9 ��6 � ��6 ; ��6<;���4 9 ��;�2 � 2 787 á!2 7 58¶¥Se`©�BjP(I.abå�N�@�FH@�?JI.=�KMC�B(K�P�X�?AãÉB(CÇ?A=�@�©�BGå�X�B(K�B�=]@ªtI.X�¬ ª�B�X�BEå�B�X" ®I.X�a�B(C ã]dâ@�©�B�P(I.=�K�@�FH=T@�å�X�B(K�K�N�X�BEn�I.=T@�B 3 FHX�QJI§a�B�@�©�I]C ª5?A@�©�Ø.FHX�?ÃFHã�QJB�K�©"FHåÉB�I G@�©�Bã�I�� +,2�2 7 8¶¥Ee`©�B�B�QÃF.K�@�?JP�P(I.=�K�@�FH=]@�KWªtB�X�BkC�B�@�B�X�ab?A=�B(Cxã]dâFÇØ:B�X�K�?JI.= + �:; � 2 789 8�I «@�©�B�K�@�X�FH?A=���'�N�P�@�N"FH@�?JI.=a�B�@�©�I�C�+,2 787 á!2 786 8¶¥j^MQA@�©�I.N�[8© @�©�BWa�B�@�©�I�C�K�B(B�a�KG@�I�ã�B×K�QJI�ª�B�XcP(I.=TØ:B�X�[:B�=T@z@�©"FH= K�I.a�B�a�B�@�©�I�C�KGª5?A@�©U���B(C�K�©"FHå�BWI u@�©�Bzå�B�X�?JI�CO?JPzã�I�� +,2 7�� ��2 7 5�89�É@�©�?JKGCO?JK�F.COØ8FH=T@�FH[:B×?JK���?A= I.N�XGI.å�?A=�?JI.=1� ®N�QAQAdEP(I.abå�B�=�K�FH@�B(CãTd�K�?Aabå�QA?JP�?A@¶d�I �@�©�B>a�B�@�©�I]CkFH=�C�@�©�B ÊF.P�@u@�©"FH@5FHQAQ"@�©�B>B�QÃF.K�@�?JPMP(I.=�K�@�FH=T@�K5FHX�BMP�FHQJP�N�QÃFH@�B(Ckª5?A@�©�?A=kFb±�³�°]Í.ºJµX�N�= CON�X�?A=�[�ª5©�?JP�© FHQJK�I�@�©�B �®B�&TN�?AQA?Aã�X�?AN�a*�zX�B� B�X�B�=�P(BÇK�@�FH@�B�?JKWC�B�@�B�X�ab?A=�B(C�¥ �®^>K�@�©�BkC�B�@�B�X�ab?A="FH@�?JI.=qI @�©�BcX�B� B�X�B�=�P(BzK�@�FH@�Bcª5?A@�©�@�©�B�K�FHa�Bcå�X�B(P�?JK�?JI.=�?A=�F�K�B�å"FHX�FH@�BcX�N�=�ªtI.N�QJC�X�B�&TN�?AX�BWFbX�N�=�I �F�P(I.abå"FHX�FHã�QJBQJB�=�[8@�©1��@�©�?JK>K�F(Ø:B(KmFHãÉI.N�@ �87 åÉB�X�P(B�=]@>I S@�©�BcK�?Aa�N�QÃFH@�?JI.=�@�?Aa�B8¥ ��e`©�BcB�QÃF.K�@�?JPzP(I.=�K�@�FH=T@�KmP�FH=Eã�BcI.ã�@�FH?A=�B(C?A=âF�K�?A=�[8QJBbX�N�=ßFHQJK�I�ãTd K�I.a�B�I.@�©�B�Xza�B�@�©�I�C�K�+ 6 9 � 6 ; � 2 7 6�8 ®I.Xcª5©�?JP�©1�r©�I�ªtB�Ø:B�X���F.KzªtB�QAQ`F.K$ I.Xca�I8K�@I >I.@�©�B�X׬�=�I�ª5= a�B�@�©�I]C�K��SN�K�?A=�[ I >B���å�QA?JP�?A@×ab?JP�X�I8K�P(I.å�?JP* I.X�azN�QÃF.B% I.X�@�©�Bkå�X�B(K�K�N�X�B �®I.XbB�Ø:B�= ®I.XW?A@�K

6

Page 5: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

C�B�X�?AØ8FH@�?AØ:B(K + 6 9 �12 7 6 8 ��?JK«X�B�&]N�?AX�B(C�¥ 2 =E@�©�BcP�F.K�BcI uFH=�?JK�I.@�X�I.å�?JP�FH=�C�=�I.=��¶P(B�=T@�X�FHQra�I.QJB(P�N�QÃFHXM?A=T@�B�X�F.P�@�?JI.=�K@�©�B�ab?JP�X�I8K�P(I.å�?JPkå�X�B(K�K�N�X�B�?JK��Z©�I�ª�B�Ø:B�X��uI ®@�B�=ßB��Oå�X�B(K�K�B(CxãTd§X�FH@�©�B�XbP(I.abå�QA?JP�FH@�B(C� I.X�azN�QÃF.B8¥ ^Må�å�QAd�?A=�[@�©�BEå�X�B(K�B�=T@�a�B�@�©�I�C��5I.=�B�F�Ø:I.?JC�K�CO?���B�X�B�=T@�?ÃFH@�?A=�[ @�©�B�?A=T@�B�X�F.P�@�?JI.=�åÉI.@�B�=]@�?ÃFHQGF.K�ªtB�QAQjF.K�C�B�X�?AØ�?A=�[ßFH=�C?Aabå�QJB�a�B�=T@�?A=�[�@�I�@�©�Bcå�X�I.[8X�FHa @�©�Bcab?JP�X�I8K�P(I.å�?JP) I.X�azN�QÃF.B) I.XM@�©�Bcå�X�B(K�K�N�X�B%�®I.X>@�©�BzB�QÃF.K�@�?JPWP(I.=�K�@�FH=]@�K���¥Y>=�BuP�FH=W=�I.@�?JP(Bt@�©"FH@Û@�©�BuK�FHa�B�?JK_@�X�N�B3 I.XrF5a�B�@�©�I�C%+ 6�6 � �87 8�ª5©�?JP�©W?JKÛã"F.K�B(CzI.=z=]N�a�B�X�?JP�FHQ�CO?���B�X�B�=]@�?ÃFH@�?JI.=I �@�©�B ®X�B(B B�=�B�X�[8d�ª5?A@�© X�B(K�å�B(P�@k@�I @�©�B K�@�X�FH?A=0¥ �®e`©�B �X�B(B B�=�B�X�[8d P�FH= ãÉB I.ã�@�FH?A=�B(C��jB8¥ [�¥,�mãTd�@�©�Bp�X�B�=�¬:B�Q>�¶lÛF.C�Cxa�B�@�©�I]C + 6�6!� �87 �32�2�2 8¶¥ � 2 = @�©�B×QÃFH@�@�B�Xja�B�@�©�I�C���©�I�ª�B�Ø:B�X��ÛØ8FHX�?JI.N�KcC�B� I.X�a�FH@�?JI.=�KzFHX�I.N�=�C@�©�B�X�B� ®B�X�B�=�P(B K�@�FH@�B�©"F(Ø:B�@�IâãÉB�P(I.=�K�?JC�B�X�B(C��>FH=�C�@�©�B �X�B(B�B�=�B�X�[8dq©"F.Kk@�IâãÉB�P�FHQJP�N�QÃFH@�B(C FH@ÇB�F.P�© I @�©�B�C�B� I.X�a�FH@�?JI.=�K�¥ 2 =â[:B�=�B�X�FHQ �rI.@�©�B�XWa�B�@�©�I�C�KzX�B�&]N�?AX�BkFHQJK�I�C�B�@�B�X�ab?A="FH@�?JI.= I «@�©�B�X�B� B�X�B�=�P(B�K�@�FH@�B�?A=F.COØ8FH=�P(B���?Ê¥ B8¥mã�B� ®I.X�Bz@�©�BzX�N�= ?A=�ª5©�?JP�© @�©�BWC�FH@�F�=�B(P(B(K�K�FHX�dE@�I�C�B�@�B�X�ab?A="FH@�?JI.=§I t@�©�B�B�QÃF.K�@�?JPWP(I.=�K�@�FH=]@�KFHX�BcI.ã�@�FH?A=�B(C�¥

iGB(K�P�X�?Aã�?A=�[b@�©�BjFHå�å�QA?JB(C�K�?AazN�QÃFH@�?JI.=�@�B(P�©�=�? &]N�BjX�B�&TN�?AX�B(K`X�B(P�FHQAQA?A=�[�K�I.a�BG[:B�=�B�X�FHQ0C�B�U�=�?A@�?JI.=�K«P(I.=�P(B�X�=��?A=�[ B�QÃF.K�@�?JP�?A@¶d I >K�I.QA?JC�K%¥§e`©�?JKW?JKbC�I.=�B�?A= @�©�B* I.QAQJI�ª5?A=�[§K�N�ã�K�B(P�@�?JI.=0¥ßR]@�FH@�?JK�@�?JP�FHQ5a�B(P�©"FH=�?JP�FHQ«ã"F.K�?JKbI @�©�BWK�?AazN�QÃFH@�?JI.= @�B(P�©�=�? &]N�B×?JKmK�¬:B�@�P�©�B(C�ã�X�?JB�'�dE?A=�@�©�B�K�B(P(I.=�C�K�N�ã�K�B(P�@�?JI.=0¥ 2 =�@�©�B�@�©�?AX�C K�N�ã�K�B(P�@�?JI.=1�É@�©�Bª�F�d�?A=kª5©�?JP�©EI.=�BjF�Ø:I.?JC�K5P�FHQJP�N�QÃFH@�?A=�[�@�©�BGK�@�X�FH?A=kP(I.abå�I.=�B�=T@�KMCON�X�?A=�[b@�©�BmK�?AazN�QÃFH@�?JI.=�K=� FH=�C��O©�B�=�P(B��O@�©�B=�B(P(B(K�K�?A@ dx@�I�¬�=�I�ª @�©�BkX�B� ®B�X�B�=�P(B�K�@�FH@�B�?A=qF.COØ8FH=�P(B���?JK×K�©�I�ª5=0¥ 2 = @�©�BkQÃF.K�@ � ®I.N�X�@�©!��K�N�ã�K�B(P�@�?JI.=1��@�©�BX�B�a�FH?A=�?A=�[�C�B�@�FH?AQJK>I r@�©�BGå�B�X" I.X�a�B(CEK�?AazN�QÃFH@�?JI.=�KGFHX�Bjå�X�B(K�B�=]@�B(C�¥

� � � �������������� ���������������������������� !�����"���#�%$��"�&�����'�"�e`©�B) �X�B(BWB�=�B�X�[8d�P�©"FH=�[:B��)(+*-,/.10�2436587���P(I.X�X�B(K�å�I.=�CO?A=�[Ç@�I�F�@�©�B�X�a�I�COd]="FHab?JP�FHQAQAd�X�B�Ø:B�X�K�?Aã�QJB×B�QÃF.K�@�?JP×C�B��

I.X�a�FH@�?JI.=�I ÛFjK�I.QA?JC�N�=�C�B�X�FH=�B��O@�B�X�="FHQ�K�@�X�B(K�K�9 5;: P�FH=�ã�B5B���å"FH=�C�B(C�?A=�å�I�ªtB�X`K�B�X�?JB(K�I �@�©�B>P(I.abåÉI.=�B�=]@�KI Z@�©�BcK�@�X�FH?A=�@�B�=�K�I.X�¥�e`©�BzK�B(P(I.=�CEI.X�C�B�XMB��Oå"FH=�K�?JI.=EX�B�F.C�K=+,2�2 6 8

(+*-,/.10�2436567=<?>!@A,�B�C DE 5;: 9 5F:HGH5;:JILKM DE 5;:=NO.�P 5;:=NO. GH5;:QG NO.SR �"2��

ª5©�B�X�BT>!@A,�Bâ?JK�@�©�B�Ø:I.QAN�a�B I z@�©�B�X�B� B�X�B�=�P(B K�@�FH@�B���U ?JK�@�©�B K�dOK�@�B�a CO?Aa�B�=�K�?JI.="FHQA?A@¶d � P 5;:�NO.mFHX�B�@�©�BP(I.abå�I.=�B�=T@�KMI r@�©�BG@�B�=�K�I.X«I rB�QÃF.K�@�?JPjP(I.=�K�@�FH=T@�K)��?A=]Ø.FHX�?ÃFH=]@Mª5?A@�©�X�B(K�å�B(P�@5@�IW@�©�B: ®I.QAQJI%ª5?A=�[�X�B�å�QÃF.P(B�a�B�=T@�KI Z@�©�Bj?A=�CO?JP(B(K �SV-WYX �'Z[W]\ �^V=R4X_W`Z�Ra\��$�

G 5;:cbedgf�5ih^: I f�:"h�5 I EN f�5ih N f�:Oh N?jA< M � 6 �

?JKZ@�©�B=�®lÛFH[8X�FH=�[:B���K�@�X�FH?A=×@�B�=�K�I.X�� h 5 blk 5�m_n+5 ?JKZ@�©�B5CO?JK�å�QÃF.P(B�a�B�=T@tØ:B(P�@�I.X�� n+5 R k 5 C�B(K�P�X�?AãÉB�@�©�B`X�B� B�X�B�=�P(BK�@�FH@�BcFH=�C�@�©�BzC�B� ®I.X�a�B(CEK�@�FH@�B���X�B(K�å�B(P�@�?AØ:B�QAd + 4�2�89��FH=�C f 5 b oo"prq ¥

^`@�P(I.=�K�@�FH=T@kå�X�B(K�K�N�X�B+s ��?Ê¥ B8¥ ª5©�B�=�@�©�B�K�@�X�B(K�K�?JK�?JK�I.@�X�I.å�?JP��t9 5;: C m s�u 5;: �×?A@�?JK���©�I�ªtB�Ø:B�X��>a�I.X�BP(I.=TØ:B�=�?JB�=]@«@�I�N�K�B>I.@�©�B�X5B�QÃF.K�@�?JPGP(I.=�K�@�FH=]@�K��^vc5F:�NO.��OI.ã�@�FH?A=�B(C�ã]d�@�©�B ®I.QAQJI%ª5?A=�[� �X�B(BmB�=T@�©"FHQAå]d �xwG?Aã�ã�K ®X�B(BB�=�B�X�[8d �`B���å"FH=�K�?JI.= + ; 6 8

(zy{<?>�| b ( d *%,}.~0�2x36567 I s�>�jA<?>#|�C�KM DE 5;:=NO. vc5F:�NO. GH5;:HG N�.�R � 9 �

Page 6: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

ª5©�B�X�B > | b > @A,}Bc?JKu@�©�B>Ø:I.QAN�a�BmI 0@�©�BMX�B� B�X�B�=�P(B>K�@�FH@�B>P�©�I8K�B�=ÇF.Kt@�©�BmB�&TN�?AQA?Aã�X�?AN�a K�@�FH@�BGFH@u@�©�B>å�X�B(K�K�N�X�Bs �rFH=�C > ?JKz@�©�BbØ:I.QAN�a�B�I `@�©�B�C�B� I.X�a�B(CxK�dOK�@�B�aE¥ 2 @cP�FH=§ã�BbK�B(B�=§@�©"FH@c@�©�B�K�B(P(I.=�C§I.X�C�B�X�B��Oå"FH=�K�?JI.=I 5@�©�B� ®X�B(B�B�=T@�©"FHQAå]dâFH@c=�I.=��Ê\�B�X�IEå�X�B(K�K�N�X�Bb?JK�F &TN"F.COX�FH@�?JP ®I.X�a �_ª5?A@�©�I.N�@zQA?A=�B�FHX�@�B�X�a�K��0?A=â@�©�B�K�@�X�FH?A=P(I.abå�I.=�B�=T@�K�¥�e`©�?JK�?JKt?A=kP(I.=]@�X�F.K�@`@�Iz@�©�B ®X�B(BMB�=�B�X�[8d�B��Oå"FH=�K�?JI.= �"2��Sª5©�?JP�©�P(I.=T@�FH?A=�K`QA?A=�B�FHX�@�B�X�a�Kt?A=k@�©�BK�@�X�FH?A=�P(I.abå�I.=�B�=T@�K%¥

e`©�B�X�Bj?JKMF×K�?Aabå�QJBjX�B�QÃFH@�?JI.=Eã�B�@¶ªtB(B�=�@�©�BcB�QÃF.K�@�?JPcP(I.=�K�@�FH=T@�K vc5;:�N�.0FH=�C P 5F:�NO.3+ ; 6 �12�2 6 8 �v�5;:�NO.'C P 5;:=NO. m s d u�56N&uA:=. I u�56.uA:=N m u 5;: uONO.�j � � 67�

e`©�B�B�QÃF.K�@�?JP�P(I.=�K�@�FH=]@�Kzvc5;:=NO.5X�B�QÃFH@�B�@�©�BEK�@�X�FH?A=�P(I.abåÉI.=�B�=]@�K�� G N�.9��P�FHQJP�N�QÃFH@�B(Cgª5?A@�©�X�B(K�åÉB(P�@�@�I§@�©�BX�B� B�X�B�=�P(B�K�@�FH@�B���?Ê¥ B8¥«@�©�BWB�&]N�?AQA?Aã�X�?AN�a K�@�FH@�B�FH@m@�©�Bc?JK�I.@�X�I.å�?JPWå�X�B(K�K�N�X�B��#s �5@�I�@�©�BWP�©"FH=�[:B(KGI �@�©�BWK�@�X�B(K�K@�B�=�K�I.XMP(I.abå�I.=�B�=T@�KMª5?A@�©EX�B(K�å�B(P�@«@�I×@�©�BcK�@�FH@�BjI Z@�©�Bj?JK�I.@�X�I.å�?JPcå�X�B(K�K�N�X�B��g(+9 5;: b 9 5;:JI s�u 5;: �

(+9 5;: C EN�. vc5;:=NO. G NO. � � � �

2 =TØ:B�X�@�?A=�[ � � ��I.=�BzI.ã�@�FH?A=�K

G 5;: C EN�. � 5;:�NO.�(+9'NO.rR ��4 �

ª5©�B�X�BG@�©�BGB�QÃF.K�@�?JPjP(I.abå�QA?ÃFH=�P(B(K�� � 5;:�NO.��OFHX�BGX�B�QÃFH@�B(CÇ@�IW@�©�BGB�QÃF.K�@�?JPjP(I.=�K�@�FH=]@�Ktvc5;:=NO.�ãTd�@�©�BjB�&]N"FH@�?JI.= +,2�2 9 8

E� � �

� 5;: � � v � � NO.�C d u�56N&uA:=. I u�56.�uA:�N�jA< M � � ; �

2 Û@�©�BjK�?A=�[8QJBjP(I.abå�I.=�B�=T@�� 9�������I r@�©�BjK�@�X�B(K�K`@�B�=�K�I.X«P(I.X�X�B(K�åÉI.=�CO?A=�[b@�I×å�N�X�BG@�B�=�K�?JI.= 4 P(I.abå�X�B(K�K�?JI.=E?A=@�©�B��¶CO?AX�B(P�@�?JI.= ?JKmP�©"FH=�[:B(C ?A=OU�=�?A@�B(K�?Aa�FHQAQAd ��ã]d ( b (+9������� ��ÉFH=�C�@�©�BWI.@�©�B�XmP(I.abå�I.=�B�=T@�KzFHX�B�¬:B�å�@?A=T@�F.P�@��"@�©�B�=E@�©�BjK�@�X�FH?A=�P�FHQJP�N�QÃFH@�B(C�ª5?A@�©EX�B(K�å�B(P�@5@�Ib@�©�BjB�&]N�?AQA?Aã�X�?AN�a�X�B� B�X�B�=�P(BcK�@�FH@�Bj?JK5[8?AØ:B�=�ãTd

GQ5;: C � 5;: ���!( � ��; �

e`©TN�K���@�©�BcwrI.?JK�K�I.=EX�FH@�?JIba�B�F.K�N�X�B(C�?A=E@�©�BjCO?AX�B(P�@�?JI.=��xåÉB�X�å�B�=�CO?JP�N�QÃFHXM@�I�â?JK5[8?AØ:B�=Eã]d

� ��� C m G ���G���� C m � �������� ������� � ��5 �

e_FH¬�?A=�[�?A=]@�I�F.P(P(I.N�=T@>@�©"FH@ ��������� C ��������� �O?A@ ®I.QAQJI%ª«K ®X�I.a ��5 ��@�©"FH@

� ��� C m ������������������ R � ��� C m ������������������ � �"2 7 �

� � ��� �! )�& #"��?�=�"�� �����T� � �_�O�&�i���"����Q�[�=���?���

2 = P(I.=]@�X�F.K�@j@�IEF*'�N�?JC���ª5©�?JP�©xP�FH= ãÉB×K�?Aa�N�QÃFH@�B(C ?A=xF�åÉB�X�?JI�CO?JP×ã�I�� I `FH=§FHX�ã�?A@�X�FHX�d P�©�I8K�B�=§K�©"FHå�B��K�?Aa�N�QÃFH@�?JI.=�KEI WFâP�X�d�K�@�FHQmX�B�&]N�?AX�B�N�K�?A=�[ Fxå�B�X�?JI]CO?JP�ã�I���ª5©�?JP�©gU�@�KÇ@�Iâ@�©�B�N�=�?A@�P(B�QAQGFH@Ç@�©�B K�@�N�CO?JB(C

4

Page 7: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

@�©�B�X�a�I�COd]="FHab?JPkP(I.=�CO?A@�?JI.=�K�¥Çe`©�?JKc?JKjã�B(P�FHN�K�BkFH=Td ab?JKvU�@zã�B�@¶ª�B(B�=â@�©�B�åÉB�X�?JI�CO?JPbQÃFH@�@�?JP(B�[:B�=�B�X�FH@�B(CâãTd@�©�BSN�=�?A@ÛP(B�QAQOFH=�Cj@�©�BSå�B�X�?JI]CO?JP�ãÉI��mX�B(K�N�QA@�KÛ?A=�FHå�å�B�FHX�FH=�P(BuI �F.C�CO?A@�?JI.="FHQ �.N�=Tª�FH=]@�B(C��.?A=T@�B�X�="FHQOK�@�X�B(K�K�ª5©�?JP�©N�K�N"FHQAQAdÇa�FH¬:B(K«@�©�BjK�@�N�CO?JB(C�K�@�X�N�P�@�N�X�Bj@�©�B�X�a�I�COd�="FHab?JP�FHQAQAd�N�=�K�@�FHã�QJB8¥ 2 =E[:B�=�B�X�FHQ ��©�I%ªtB�Ø:B�X���=�B�?A@�©�B�XM@�©�BK�©"FHå�Bz=�I.XG@�©�BWK�?A\�BWI u@�©�BWN�=�?A@mP(B�QAQ�FHX�B�¬]=�I%ª5=A I.XGK�@�N�CO?JB(C K�d�K�@�B�a�K�¥>e`©�?JKGå�X�I.ã�QJB�a£P�FH= ã�BzK�I.QAØ:B(C�ãTdN�K�?A=�[�@�©�B�n�I.=T@�B 3 FHX�QJI�P(I.N�=]@�B�X�å"FHX�@ +,2�2 7 8rI �@�©�BWwrFHX�X�?A=�B�QAQJI�¶omFH©�a�FH= ?JC�B�F +,2�2 6 89��?Ê¥ B8¥«ã]d�FHQAQJI�ª5?A=�[Ç@�©�BK�©"FHå�B�FH=�C @�©�BbK�?A\�B�I `@�©�B×å�B�X�?JI]CO?JPbã�I�� �®C�B(K�P�X�?Aã�B(C ãTd F.C�CO?A@�?JI.="FHQtC�B�[8X�B(B(K�I . ®X�B(B(C�I.a*�m@�I�P�©"FH=�[:B�?A=K�N�P�©xFkª�F(d�@�©"FH@��ÛFH@cB�&]N�?AQA?Aã�X�?AN�a �0@�©�B � F�Ø:B�X�FH[:B��mãÉI���U�@�Kj@�©�BbB�&]N�?AQA?Aã�X�?AN�a£N�=�?A@cP(B�QAQ�P(I.X�X�B(K�å�I.=�CO?A=�[E@�I@�©�B×P(I.=�CO?A@�?JI.=�KzK�@�N�CO?JB(C�¥ 2 = K�N�P�© K�?AazN�QÃFH@�?JI.=�K��Ûª5©�?JP�©§P�FH= ã�B�å�B�X" I.X�a�B(C ?A=�@�©�B ®X�FHa�B�ªtI.X�¬ I tØ8FHX�?JI.N�K[:B�=�B�X�FHQA?A\%FH@�?JI.=�KcI �@�©�BWP(I.=�K�@�FH=T@Gå�X�B(K�K�N�X�B×B�=�K�B�a�ã�QJB + 6 � �32 7 2��32 786 ��2 7 5 ��2�2 6!��2�2 � 89��?A@G?JKGP(I.=TØ:B�=�?JB�=]@c@�IC�B(K�P�X�?Aã�BW@�©�B�å�B�X�?JI�CO?JP�ã�I���ãTd�@�©�BWã�I���a�FH@�X�?>� ��� ��ª5©�?JP�© P(I.QAN�ab=�K�FHX�B) I.X�a�B(C�ãTd�@�©�BWP(I.abå�I.=�B�=T@�KzI @�©�BcØ:B(P�@�I.X�KmC�B(K�P�X�?Aã�?A=�[�@�©�Bcå�B�X�?JI]CO?JPjã�I�� +,2�2 � 8¶¥`e_I�F(Ø:I.?JC�X�I.@�FH@�?JI.=�K>I S@�©�B�K�d�K�@�B�a ��@�©�Bc=]N�azã�B�XmI S@�©�BP(I.abå�I.=�B�=T@�K�I É@�©�B5ã�I��×a�FH@�X�?>��K�©�I.N�QJCbã�B5B�&TN"FHQ�@�Ic@�©�B5=TN�a�ãÉB�X�I É@�©�B5?A=�C�B�å�B�=�C�B�=T@�P(I.abåÉI.=�B�=]@�KtI �@�©�BK�@�X�FH?A=k@�B�=�K�I.X��^U d U I K jA< M ¥`Y>=�B>I Ûå�I8K�K�?Aã�?AQA?A@�?JB(Kt@�I �N�QVU�QAQÉ@�©�?JK�X�B�&TN�?AX�B�a�B�=]@`?JKt@�I�å�N�@`K�I.a�BMX�B(K�@�X�?JP�@�?JI.=�KI.=�å�I8K�K�?Aã�QJBzCO?AX�B(P�@�?JI.=�KmI �@�©�BzãÉI��EB(CO[:B(K +,2�2 7 8¶¥5^>=�I.@�©�B�XMå�I8K�K�?Aã�?AQA?A@ d �ÉF.C�I.å�@�B(C�?A=�@�©�Bzå�X�B(K�B�=T@må"FHå�B�XmF.Ka�I.X�BmP(I.=TØ:B�=�?JB�=T@ I.XtP�FHQJP�N�QÃFH@�?JI.=�K��]?JKt@�I�¬:B(B�å�@�©�BMãÉI���a�FH@�X�?>��K�d�aba�B�@�X�?JP>CON�X�?A=�[W@�©�B>K�?AazN�QÃFH@�?JI.=�K +,2�2�48¶¥

iGB�=�I.@�?A=�[×@�©�BMa�FH@�X�?>��I _@�©�BMX�B� B�X�B�=�P(BGK�@�FH@�BMã]d�� b �%@A,}B%��ª5©�?JP�©�?JKt@�FH¬:B�=EF.Ku@�©�BjF(Ø:B�X�FH[:B(�®B�&]N�?AQA?Aã��X�?AN�a*��ã�I��Ça�FH@�X�?>� ��� ��FH@«@�©�BGå�X�B(K�K�N�X�B s ����I.=�BcP�FH=Eª5X�?A@�Bj@�©�BjK�@�X�FH?A=E@�B�=�K�I.X«?A=�@�©�B I.X�a

� b � d �JR�� j�C���� ­ � � � � � �� ­ m���� < M R �"2�2��

ª5©�B�X�Bc@�©�Bca�FH@�X�?>���ß?JK>F.K�K�N�a�B(C�@�Ibã�BcK�d�aba�B�@�X�?JP*��ª5©"FH@«?Aabå�QA?JB(K>@�©"FH@�� ?JK>FHQJK�I�K�d]aba�B�@�X�?JP������ ­ ?JK@�©�Bja�FH@�X�?>�E?A=]Ø:B�X�K�BzI Z@�©�BjX�B� B�X�B�=�P(Bcã�I���a�FH@�X�?>� �ÉFH=�C � ?JK«@�©�BjN�=�?A@Ma�FH@�X�?>��I ZCO?Aa�B�=�K�?JI.="FHQA?A@ d�U�¥ue`©�BØ:I.QAN�a�BcI Z@�©�Bjã�I��Ç?JK«B�&TN"FHQÛ@�I×@�©�BzFHã�K�I.QAN�@�BjØ8FHQAN�BcI Z@�©�BjC�B�@�B�X�ab?A="FH=T@GI r@�©�Bjã�I��Ça�FH@�X�?>�

> d � j�C�������� d ��j�� �"2 6 �

e`©�BWP(I.=OU�[8N�X�FH@�?JI.="FHQ�å"FHX�@�?A@�?JI.= �N�=�P�@�?JI.= I ���å"FHX�@�?JP�QJB(K���ª5©�?JP�©xFHX�BWP�QJI8K�B(C�?A=§F�å�B�X�?JI]CO?JPWã�I���� d � jI.ã�@�FH?A=�B(C ã]d FÇC�B� I.X�a�FH@�?JI.= �®C�B(K�P�X�?Aã�B(C ãTd @�©�BbK�@�X�FH?A= � �mI t@�©�B×X�B� B�X�B�=�P(Bbã�I������[| b � @A,}B C � d"! j��P�FH=Eã�BGª5X�?A@�@�B�=�F.K

#%$&� d � j(' C)�+*-,/. m *0$&� d � j('Z21 3C K��4257698;:+<>=>? 8A@�< 5 =-B 8C@D< �+*E, . m�FZ21 3 R �"2 9 �

ª5©�B�X�B ? 5 � B 5 � V C K R � � � RG� ��C�B�=�I.@�B�@�©�B�å"FHX�@�?JP�QJB�åÉI8K�?A@�?JI.=�K�FH=�C�I.X�?JB�=T@�FH@�?JI.=�K�� F ?JK�@�©�BE?A=]@�B�X�F.P�@�?JI.=B�=�B�X�[8d � Z�?JK>@�©�B×h`I.QA@�\(a�FH=�= P(I.=�K�@�FH=T@���1�?JKm@�©�BW@�B�abåÉB�X�FH@�N�X�B��0FH=�C *0$&� d � j('S?JKm@�©�B= ®X�B(B�B�=�B�X�[8d�I u@�©�BK�dOK�@�B�a�FH@5@�©�BcK�@�X�FH?A= G ¥

p�I.X ®N�X�@�©�B�XMP(I.=�K�?JC�B�X�FH@�?JI.=�K>?A@5?JK«P(I.=TØ:B�=�?JB�=]@>@�I�C�B�U�=�Bj@�©�B I.QAQJI�ª5?A=�[�å"FHX�@�?A@�?JI.= �N�=�P�@�?JI.=

#lC 5 = ��HJIKHML�NPOQ �+*E,�R m s�> d � jZ21 S #%$&� d � j(' �"2 67�

;

Page 8: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

ª5©�B�X�B`@�©�B`?A=T@�B�[8X�FH@�?JI.=kI�Ø:B�X�@�©�B5K�@�X�FH?A=b@�B�=�K�I.XSP(I.=�P(B�X�=�KtFHQAQ�?A@�K D8D�� ­ <� ?A=�C�B�åÉB�=�C�B�=]@tP(I.abå�I.=�B�=T@�K�¥Z<mK�?A=�[

�"2 9 �5FH=�C � 9 ��I.=�BzI.ã�@�FH?A=�K

# C 5 = � H IKHMLENPOQ �+*-, R}m s > d � j I *0$&� d � j('Z21 SC 5 = � H IKHMLENPOQ �+*-, R m y $&� d � j('Z21 SC �+*E,�R m y $&� d"! j('Z21 S 5 = � HJIKHML�NPOQ

� �+*E, ��m >#|M Z21 DE 5;:�N�. vc5;:=NO. GH5;:QG NO.��� R �"2 � �

ª5©�B�X�B>@�©�B«QÃF.K�@uB�&]N"FHQA?A@¶d�?JKuP(I.X�X�B(P�@. ®I.XuK�@�FHã�QJB«X�B� B�X�B�=�P(B>K�@�FH@�B(K:�®C�B(K�P�X�?Aã�B(C�ã]dbåÉI8K�?A@�?AØ:BMCO?VU�=�?A@�B &]N"F.COX�FH@�?JP I.X�a � 67� ��ª5©�B�=E@�©�BcK�dOK�@�B�a ?JK5QÃFHX�[:BzB�=�I.N�[8©1��?Ê¥ B8¥Sª5©�B�=E@�©�BcK�@�X�FH?A=�'�N�P�@�N"FH@�?JI.=�KmFHX�BcK�a�FHQAQÊ¥

e`©�B: I.QAQJI�ª5?A=�[�X�B�QÃFH@�?JI.=�P(I.a�B(K ®X�I.a �"2 � �`FH=�C � ; ���

GH5;:HG N�.��C Z21 � 5;:�NO.> | R �"2�4 �

ª5©�B�X�B

� b�� = � HJIKHML�NPOQ � �+*E, d m y $&� d � j(' <&Z21 j� = � H IKHMLENPOQ �+*-, d m y $&� d � j(' <&Z21 j �"2 ; �

C�B�=�I.@�B(Kr@�©�B�@�©�B�X�a�I�COd]="FHab?JP5F�Ø:B�X�FH[8?A=�[GI �F �N�=�P�@�?JI.= � ª5?A@�©W@�©�B�å"FHX�@�?A@�?JI.= ®N�=�P�@�?JI.=��"2 67��¥ 2 =�å"FHX�@�?JP�N�QÃFHX��@�©�BzF�Ø:B�X�FH[:B*�®B�&]N�?AQA?Aã�X�?AN�a*�`Ø:I.QAN�a�BzFH@5@�©�Bjå�X�B(K�K�N�X�B s�?JK«P�FHQJP�N�QÃFH@�B(C�F.K

>�|�C ������� d ��j��� � �"2�; �

2 @�?JK0ªtI.X�@�©�@�IMF.C�Cj@�©"FH@_@�©�B�P(I.abå�X�B(K�K�?Aã�?AQA?A@ d ����� C m ­����� o �o |�� � �HP�FH=cã�B�I.ã�@�FH?A=�B(C$ ®X�I.a @�©�B�B�&]N"FH@�?JI.= �

� d ([> j ��� b � = � H IKHMLENPOQ d ([> j � �+*-, d m y $&� d � j(' <&Z21 j� = � HJIKHML�NPOQ �+*E, d m y $&� d � j(' <&Z21 jC Z21 > | � � � �"2�5 �

� � � ������� "�����?������� ����� � �+� � ��� "�� �' ��� " ��{�������"�! ��&�e`©�BMK�@�X�FH?A=�@�B�=�K�I.Xt?JKtC�B�U�=�B(C�ª5?A@�©�X�B(K�å�B(P�@u@�Iz@�©�B«X�B� B�X�B�=�P(B>K�@�FH@�B«ª5©�?JP�©ÇP(I.X�X�B(K�å�I.=�C�Ku@�Iz@�©�B>B�&]N�?AQA?Aã��

X�?AN�a K�@�FH@�B«I �@�©�B«K�dOK�@�B�a FH@�@�©�B5[8?AØ:B�=�å�X�B(K�K�N�X�B8¥�R]?A=�P(B��]?A=�[:B�=�B�X�FHQ �T@�©�B>B�&TN�?AQA?Aã�X�?AN�aÝK�@�FH@�B5?JKu=�I.@�¬]=�I%ª5=?A=EF.COØ.FH=�P(B(��?Ê¥ B8¥Zã�B� ®I.X�B>@�©�BGK�?AazN�QÃFH@�?JI.=!���"I.=�B>ab?A[8©]@`@�©�?A=�¬�@�©"FH@`@�I×P�FHQJP�N�QÃFH@�B>@�©�Bm@�©�B�X�a�I�COd]="FHab?JPcF�Ø:B�X"�FH[:B(KMI Z@�©�B I.X�a �"2 ; ��ª5©�?JP�©�C�B�åÉB�=�C�I.=E@�©�BjK�@�X�FH?A=�P(I.abå�I.=�B�=T@�K��"?A@«?JK5=�B(P(B(K�K�FHX�d�@�Ibå�B�X" I.X�a¢FH=�?A=�?A@�?ÃFHQX�N�=§@�IEC�B�@�B�X�ab?A=�B�@�©�B×X�B� ®B�X�B�=�P(B�K�@�FH@�B8¥ �®n�I.X�B(I�Ø:B�X��ZF.Kc@�©�BbX�B� B�X�B�=�P(B�K�@�FH@�B�azN�K�@cã�BbC�B�@�B�X�ab?A=�B(C§Ø:B�X�dF.P(P�N�X�FH@�B�QAd �Z@�©�B�?A=�?A@�?ÃFHQtX�N�=âªtI.N�QJCâ=�I.@�ã�B�P(I.abå�N�@�FH@�?JI.="FHQAQAdâP�©�B�FHå0¥ � e`©�B�å�X�B(K�B�=T@��SP(I.=�K�@�FH=T@Wå�X�B(K�K�N�X�B

;

Page 9: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

a�B�@�©�I�C C�I]B(KG=�I.@GX�B�&]N�?AX�B���©�I�ª�B�Ø:B�X��rFH=]d�B��O@�X�F�?A=�?A@�?ÃFHQSX�N�= @�IkC�B�@�B�X�ab?A=�B�@�©�B×X�B� ®B�X�B�=�P(BbK�@�FH@�B8¥�e`©�?JKj?JK?AQAQAN�K�@�X�FH@�B(C�ãÉB�QJI%ª ®I.XGFb@¶ª�I�¶CO?Aa�B�=�K�?JI.="FHQuK�dOK�@�B�aE¥)�®e`©�B�@�©�X�B(B��¶CO?Aa�B�=�K�?JI.="FHQSP�F.K�B�?JK>CO?JK�P�N�K�K�B(CE?A=�C�B�@�FH?AQB�QJK�B�ª5©�B�X�B +,2�2 ; 8¶¥ �

e`©�B>?A=T@�B�[8X�FHQJK5I�Ø:B�X�@�©�BmK�@�X�FH?A=kP(I.abå�I.=�B�=T@�K5P�FH=kã�BMP(I.=TØ:B�X�@�B(CÇ?A=]@�IW?A=T@�B�[8X�FHQJK`I�Ø:B�X`?A=�C�B�å�B�=�C�B�=T@«P(I.a��å�I.=�B�=T@�KuI �@�©�B5ã�I��×a�FH@�X�?>��¥S<mK�?A=�[j@�©�B I.X�azN�QÃF��"2�2��SFH=�C�C�B�=�I.@�?A=�[z@�©�B��TF.P(I.ã�?ÃFH=�I �@�©�B5@�X�FH=�K" I.X�a�FH@�?JI.=d�� ��� R � ��� R � ��� j#� d G ��� R G ��� R G ��� j�ã]d X d � R�� j�I.=�B P�FH=�B��Oå�X�B(K�Kk@�©�B F(Ø:B�X�FH[:B ��ª5?A@�© X�B(K�åÉB(P�@Ç@�I � ��?A=L &É¥ �"2 ; ��ãTdÇ@�©�BGX�FH@�?JI�I Z@�©�BzF�Ø:B�X�FH[:B(KMª5?A@�©EX�B(K�åÉB(P�@5@�I0� �

� SC � X d � R�� j ���< X d � R�� j �� R � 687 �

ª5©�B�X�B�� ®I.X � b � ��� 8C@D< R B 8A@�< R � d � R�� j � ãÉB�?A=�[qFH=]d �®K�a�I�I.@�©!�� �N�=�P�@�?JI.= I �@�©�B P(I.=OU�[8N�X�FH@�?JI.= I WF@¶ª�I�¶CO?Aa�B�=�K�?JI.="FHQZK�d�K�@�B�a �O@�©�BzF(Ø:B�X�FH[:B(K � � � ���FHX�BcC�B�U�=�B(C�F.K

� � b � = � ��� � = � ��� � = � ��� > @ � = � 8A@�< � =-B 8A@�< � d � 8A@�< R B 8A@�< R �JR�� j��+*E, $ m d F I s�> jA<&Z21 '� = � ��� � = � ��� � = � ��� > @ � = � 8A@�< � =-B 8C@D< �+*E, $ m d F I s�> jA<&Z21 ' � � 6 2��

eÛI�B�QA?Aab?A="FH@�B�@�©�BbK�@�X�FH?A= ®X�I.a£@�©�Bbã�I.N�=�C�FHX�d�C�B�å�B�=�C�B�=�P(B(KzI `@�©�Bb?A=]@�B�[8X�FHQJKc?A= � 6 2����Û@�©�B�� =�I.X�a�FHQA?A\�B(C���®K�P�FHQJB(Cx@�I�F�N�=�?A@WK#&]N"FHX�B��Gå�I8K�?A@�?JI.=�K�I 5@�©�B�å"FHX�@�?JP�QJB(K�� � 5 C ��� � ? 5 � V{C K R � � � RG� ��FHX�B�N�K�B(C�?Z@�©�B�ã�I��a�FH@�X�?>�/�ß?JK«K�d�aba�B�@�X�?JP8¥�p�I.XM@�©�BjK�d]aba�B�@�X�?JPcãÉI��ka�FH@�X�?>��?A=E@ ªtI�CO?Aa�B�=�K�?JI.=�K>@�©�B��TF.P(I.ã�?ÃFH=

X d � R�� j b f�d G ��� R G ��� R G ��� jf�d � ��� R � ��� R � ��� j

C d�� ��� I � ��� j d�� ���� m � ����� ��� jM d�� ���� m �!�����!��� j��

C`X�� d ��jiX�� d � j � 686 �

?JK�F�å�X�I�CON�P�@�I GFA ®N�=�P�@�?JI.= ª5©�?JP�©�C�B�å�B�=�C�K�I.=�QAd I.= @�©�B�P(I.abåÉI.=�B�=]@�K�I G@�©�BÇãÉI��ßa�FH@�X�?>���D� �tFH=�CqF ®N�=�P�@�?JI.=qª5©�?JP�©�C�B�å�B�=�C�K�I.=�QAdßI.= @�©�BEP(I.abåÉI.=�B�=]@�K�I m@�©�BÇX�B� ®B�X�B�=�P(B�ã�I�� a�FH@�X�?>����� �uª5©�?JP�©�P�FH=�ãÉB@�©�I.N�[8©T@×I >F.K*��N�=�¬�=�I�ª5=!�zP(I.=�K�@�FH=]@�K�¥Ee`©TN�K��_@�©�B�@�©�B�X�a�I]COd�="FHab?JPÇF(Ø:B�X�FH[:BkI `@�©�B �N�=�P�@�?JI.= � P�FH=ßãÉBª5X�?A@�@�B�=�F.K

� C � X�� ��#< X�� ��C � = � ��� � = � ��� � = � ��� � = � 8C@D< � =EB 8C@D< � �+*E, d m y � 567g@�� <&Z21 j� = � ��� � = � ��� � = � ��� � = � 8A@�< � =-B 8A@�< �+*-, d m y � 567g@�� <&Z21 j R � 689 �

ª5©�B�X�Bj@�©�B(� ab?JP�X�I8K�P(I.å�?JP$ ®X�B(BjB�=T@�©"FHQAåTd �

y � 567g@�� C Z21%$ d � I K j�����> I ������� d ��j' m F I s�> R � 6 67�

C�I�B(Kj°�·8²�C�B�å�B�=�CEI.=�@�©�BjX�B� B�X�B�=�P(BcK�dOK�@�B�aE¥e`©�B5B�&]N"FH@�?JI.= � 689 �rK�@�FH@�B(KZ@�©"FH@uFH@S?JK�I.@�X�I.å�?JP`å�X�B(K�K�N�X�B`@�©�B5n�I.=T@�B 3 FHX�QJIjK�?AazN�QÃFH@�?JI.=�P�FH=×ã�B`åÉB�X" I.X�a�B(C

ËS³®²�¿�·.´O²"¬�=�I�ª5?A=�[W@�©�B>K�@�X�N�P�@�N�X�FHQÉå"FHX�FHa�B�@�B�X�K=��?Ê¥ B8¥Z@�©�B>X�B� B�X�B�=�P(B>K�@�FH@�B��uI 0@�©�BmK�d�K�@�B�aÝFH@`B�&TN�?AQA?Aã�X�?AN�a ?A=F.COØ8FH=�P(B ��?Ê¥ B8¥Zã�B� ®I.X�BMåÉB�X" I.X�ab?A=�[W@�©�BMK�?Aa�N�QÃFH@�?JI.=kX�N�=k?A=�ª5©�?JP�©Ç@�©�BMB�QÃF.K�@�?JP>å�X�I.åÉB�X�@�?JB(K`I 0@�©�B>K�d�K�@�B�aÝFHX�B

5

Page 10: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

P(I.abå�N�@�B(C0��¥ke`©�?JKj?JKc?A=§P(I.=]@�X�F.K�@z@�I�@�©�B�[:B�=�B�X�FHQuP�F.K�B�I «FH=âFH=�?JK�I.@�X�I.å�?JP�K�@�X�B(K�Kjª5©�B�=§@�©�B�ab?JP�X�I8K�P(I.å�?JPB�=T@�©"FHQAå]d�?JKGFH= B���å�QA?JP�?A@: ®N�=�P�@�?JI.=�I u@�©�BWK�@�X�FH?A= FH=�C�ª5©�B�= I.=�B�©"F.Km@�I�¬�=�I�ª�@�©�BWX�B� ®B�X�B�=�P(BWK�@�FH@�B�Ü�µ�¸(·.½�µ@�©�BcK�?Aa�N�QÃFH@�?JI.=�K�¥

e`©�B`K�?Aabå�QJB(K�@ZK�P�©�B�a�B`@�ImC�B�@�B�X�ab?A=�B � 5;:�N�.]?A= �"2�4 �Û?JK_@�IGK�@�I.X�B�CON�X�?A=�[j@�©�B`K�?AazN�QÃFH@�?JI.=�K�@�©�BuØ8FHQAN�B(KSI "@�©�Bã�I���a�FH@�X�?>�bP(I.abå�I.=�B�=T@�K � 5F: ?A=�F«U�QJB8¥Z^ �@�B�XrU�=�?JK�©�?A=�[j@�©�B`X�N�=1�:@�©�B�K�@�I.X�B(CbC�FH@�FGP�FH=Wã�B�N�K�B(C×@�IGP(I.abå�N�@�B@�©�BbF(Ø:B�X�FH[:B �®B�&]N�?AQA?Aã�X�?AN�a*�mØ8FHQAN�B(KjI u@�©�BbP(I.abå�I.=�B�=T@�KcI �@�©�B�ã�I���a�FH@�X�?>� � � 5;: �C d�� @A,�B�j 5;: b � 5;: ��ãTdK�N�ã�K�@�?A@�N�@�?A=�[ � C � 5;: ?A= � 689 ��¥�e`©�BÇP�FHQJP�N�QÃFH@�B(CßB�&]N�?AQA?Aã�X�?AN�a ��X�B� B�X�B�=�P(B��cØ8FHQAN�B(K×P�FH=â@�©�B�=ßã�B�N�K�B(Câ@�IP(I.abå�N�@�Bj@�©�BcK�@�X�FH?A=�@�B�=�K�I.XMP(I.abå�I.=�B�=T@�K�� GQ5;: �Oª5©"FH@���?A=E@�N�X�=1�Oa�FH¬:B(KMåÉI8K�K�?Aã�QJBjP�FHQJP�N�QÃFH@�?JI.=�I r@�©�BcB�QÃF.K�@�?JPP(I.abå�QA?ÃFH=�P(B(KGF.P(P(I.X�CO?A=�[�@�I � 687 ��¥

�«µ�Æ�¼.½�Ì�� 2 @E?JK�ªtI.X�@�©�@�IgF.C�C @�©"FH@�@�©�Bxa�B�@�©�I]C N�K�B(C ?A=s@�©�B§å�X�B(K�B�=]@�ª�I.X�¬ Å:·%µ�±§°�·:²cX�B�&]N�?AX�BxP�X�B��FH@�?A=�[§FH=Td U�QJB�?A=ߪ5©�?JP�© @�©�BÇC�FH@�F�FHX�BkK�@�I.X�B(C�¥ DmFHa�B�QAd ��?A@) I.QAQJI�ª«K ®X�I.a �"2�2���� �"2�4 �WFH=�C �"2�; �c@�©"FH@W@�II.ã�@�FH?A= @�©�B×P(I.abå�QA?ÃFH=�P(B(Kc?A@G?JKjB�=�I.N�[8© @�I�F(Ø:B�X�FH[:B�CON�X�?A=�[�@�©�B×K�?Aa�N�QÃFH@�?JI.=�K�F� B�ª�a�I.=�I.ab?ÃFHQJKzP(I.=�K�?JK�@�B(CI G@�©�BÇãÉI��ßa�FH@�X�?>�qP(I.abå�I.=�B�=T@�K�I Gå�I�ªtB�X�K�=�I.@�B���P(B(B(CO?A=�[ ®I.N�X +,2�2 ; 8¶¥ e`©�BEF(Ø:B�X�FH[:BEØ8FHQAN�B(K�I G@�©�B(K�Ba�I.=�I.ab?ÃFHQJK���?A=�P�QAN�CO?A=�[�@�©�BzF�Ø:B�X�FH[:BzØ8FHQAN�B(KMI Z@�©�Bcã�I���a�FH@�X�?>�EP(I.abå�I.=�B�=T@�Kmª5©�?JP�©�C�B�U�=�Bc@�©�BjX�B� B�X�B�=�P(BK�@�FH@�B��§P�FH= ã�BqK�N�ã�K�@�?A@�N�@�B(C @�I @�©�B ®I.X�a�N�QÃF �"2�4 �âFH@x@�©�BgB�=�C I �@�©�B�X�N�= ª5©"FH@â[8?AØ:B(Kâ@�©�BgB�QÃF.K�@�?JPP(I.abå�QA?ÃFH=�P(B(K�¥�f>I%ªtB�Ø:B�X��5P�X�B�FH@�?JI.=�I cF U�QJB�ª5?A@�©q@�©�B � ©�?JK�@�I.X�d ��I j@�©�B�ã�I�� B�Ø:I.QAN�@�?JI.=g=�I.@�I.=�QAdßI ��B�X�KFßK�?Aabå�QJB FH=�C P(I.=TØ:B�=�?JB�=]@�K�P�©�B�a�B ®I.XÇC�B�@�B�X�ab?A="FH@�?JI.=sI z@�©�B P(I.abå�QA?ÃFH=�P(B(K�� � 5;:�NO.��«ã�N�@�FHQJK�Iß©�B�QAå�KÇ@�IB(K�@�?Aa�FH@�Bj@�©�BzB�&TN�?AQA?Aã�X�FH@�?JI.= � @�?Aa�B��"FH=�C�@�©�BjK�@�FH@�?JK�@�?JP�FHQ_B�X�X�I.X�KMI Z@�©�BjX�B(K�N�QA@�K«I.ã�@�FH?A=�B(C�¥

� � � ���������� ���r� � � ��� " ����?��������

2 = @�©�B�n 3 K�?AazN�QÃFH@�?JI.=�K×CO?JK�P�N�K�K�B(C ?A=§@�©�?JK�å"FHåÉB�Xz@¶ªtI�¬�?A=�C�KzI 5@�X�?ÃFHQ�a�I�Ø:B(KWª�B�X�B�å�B�X" ®I.X�a�B(C�¥Çe`©�BU�X�K�@�P(I.=�P(B�X�=�B(C �®K�?AazN�QA@�FH=�B(I.N�K���P�©"FH=�[:B(K�I G@�©�BÇa�I.QJB(P�N�QÃFHX�a�F.K�KbP(B�=]@�X�BEå�I8K�?A@�?JI.=�FH=�C @�©�BÇa�I.QJB(P�N�QÃFHXI.X�?JB�=T@�FH@�?JI.=1?«@�©�BEF.P(P(B�å�@�FH=�P(B�X�FH@�?JI ª�F.K׬:B�å�@�P�QJI8K�Bk@�I 987 å�B�X�P(B�=T@�¥ e`©�Bka�F���?Aa�FHQ>FHabå�QA?A@�N�C�B(K�I >@�©�BFHQAQJI�ª�B(C P�©"FH=�[:B(K×I «@�©�B�@�X�FH=�K�QÃFH@�?JI.="FHQ5C�B�[8X�B(B(K×I �X�B(B(C�I.a FH=�Câ@�©�B�X�I.@�FH@�?JI.="FHQ5I.=�BA��?A=âX�F.CO?ÃFH=�K��jª�B�X�B@�©�B�K�FHa�B8¥ �ÊY>@�©�B�XWP�©�I.?JP(B(K��rB8¥ [�¥kã"F.K�B(C§I.=xB�&]N"FHQA?A@¶d§I MF(Ø:B�X�FH[:B�¬�?A=�B�@�?JP�B�=�B�X�[8?JB(K�I 5@�X�FH=�K�QÃFH@�?JI.="FHQ5FH=�CX�I.@�FH@�?JI.="FHQjC�B�[8X�B(B(KÇI $ �X�B(B(C�I.a +,2�2 7 8>[8?AØ:B�@�©�B�K�FHa�B�X�B(K�N�QA@�K��`ª5?A@�©�?A=g@�©�B�B��OåÉB�X�?Aa�B�=]@�FHQGB�X�X�I.X�¥ � e`©�BK�B(P(I.=�C�¬]?A=�C�I 0a�I�Ø:B(K���@�X�?JB(CÇFHãÉI.N�@ �x­�� � @�?Aa�B(K�QJB(K�K �X�B�&]N�B�=T@�QAd �OP(I.=�P(B�X�=�B(CÇP�©"FH=�[:B(K`I 0@�©�BmP(I.abåÉI.=�B�=]@�KI �@�©�B«K�d�aba�B�@�X�?JP«ã�I��×a�FH@�X�?>��I.=�QAd ?]@�©�B«I.X�?JB�=]@�FH@�?JI.=�K�� B 5 ��FH=�C�@�©�B«K�P�FHQJB(C�åÉI8K�?A@�?JI.=�K�� � 5 �TI �@�©�B«å"FHX�@�?JP�QJB(KªtB�X�B>=�I.@uP�©"FH=�[:B(C�¥�e`©�B(K�B«a�I%Ø:B(KtC�B�@�B�X�ab?A=�B(C�@�©�BMK�?A\�B>FH=�Cb@�©�B>K�©"FHåÉBMI 0@�©�B5ãÉI�� �OFH=�Cb@�©�B�?AX5F.P(P(B�å�@�FH=�P(BX�FH@�?JIbª`F.KMP�QJI8K�BG@�I 687 å�B�X�P(B�=T@�¥

2 @b?JK�ªtB�QAQ>¬]=�I%ª5=�@�©"FH@�@�©�B�FH=�?JK�I.@�X�I.åTdqI j@�©�B�å�B�X�?JI�CO?JP�ãÉI��qP�FH=�a�I�CO?> �d �®B�Ø:B�= &]N"FHQA?A@�FH@�?AØ:B�QAd �5K�B(BB8¥ [�¥ +,2�2�;�� 2�2�58 �c@�©�B�@�©�B�X�a�I�COd]="FHab?JPkå�X�I.å�B�X�@�?JB(KbI M@�©�BkK�@�N�CO?JB(C K�d�K�@�B�aE¥�eÛI�ab?A=�?Aab?A\�BÇ@�©�B�?A=�'�N�B�=�P(BI `@�©�BbãÉI��xFH=�?JK�I.@�X�I.åTd �ZK�FHabå�QJB(K�I `K�©"FHå�B(KcP�QJI8K�B�@�I�@�©�B�K#&]N"FHX�Bb©"F(Ø:B�ãÉB(B�=xN�K�B(C�¥�e`©�B�K�?AazN�QÃFH@�?JI.=�KWI @�©�B�åÉB�=]@�FHa�B�X�K×FH=�Câ@�©�Bk^�FH=�Câh K�@�X�N�P�@�N�X�B(KbI «@�©�B�©�B�å�@�FHa�B�X�KWªtB�X�BÇP�FHX�X�?JB(CßI.N�@) I.X�K�FHabå�QJB(K�ã�B�?A=�[P(I.=�K�B(P�N�@�?AØ:B�&]N"F.COX�N�å�QA?A=�[:KbI >FEab?A=�?Aa�N�a�K�FHabå�QJB��Zª5©�?JP�© P(I.=�K�?JK�@�B(CßI ;�©�I.X�?A\�I.=T@�FHQ5X�I�ª«KWå"FHX�FHQAQJB�Q`@�I

2 7

Page 11: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

@�©�B k � F��O?JK��0B�F.P�©§X�I�ª P(I.abåÉI8K�B(C I ; a�I.QJB(P�N�QJB(K�¥be`©�?JKcC�B�@�B�X�ab?A=�B(Cx@�©�BbK�?A\�B(KcI �@�©�BbK�@�N�CO?JB(C§K�dOK�@�B�a�K �� C�����R M?M�� R������O¥t^mKr@�©�B 3 K�@�X�N�P�@�N�X�B5I �@�©�Bt©�B�å�@�FHa�B�X�KuP�FH=�=�I.@rã�B5FHX�X�FH=�[:B(C×?A=×F� � åÉB�X�?JI�CO?JP�QÃFH@�@�?JP(B��I.=�QAd�K�FHabå�QJB(KGI ��]C M?M�� R������Ç©�B�å�@�FHa�B�X�KGª�B�X�B×K�?AazN�QÃFH@�B(C ?A=�@�©�?JKGP�F.K�B8¥G^5C�CO?A@�?JI.="FHQAQAd �0K�?AazN�QÃFH@�?JI.=�KzI � C�����R K ��� R�� �תtB�X�B>å�B�X" ®I.X�a�B(C ®I.Xt@�©�B 3 K�@�X�N�P�@�N�X�B8¥ 2 =�@�©�?JK�P�F.K�BM@�©�B«ab?A=�?AazN�a K�FHabå�QJB>P(I.=�K�?JK�@�B(CkI 4ש�I.X�?A\�I.=]@�FHQrX�I%ª«KMå"FHX�FHQAQJB�Q_@�I�@�©�B k � F��O?JK���B�F.P�©�X�I�ª�P(I.abåÉI8K�B(CEI 4ba�I.QJB(P�N�QJB(K�¥`e�d�å�?JP�FHQrQJB�=�[8@�©�K>I S@�©�BX�N�=�K5ª�B�X�BjB�&TN"FHQ�� � K � m@�X�?ÃFHQ0K�@�B�å�K5å�B�X`å"FHX�@�?JP�QJB��®P�d�P�QJB(K��3 I.X � C�������� � K � jP�d�P�QJB(K I.X � C�����R K ��� �K ��×P�dOP�QJB(K: ®I.X � C M?M�� �_FH=�C M � K �� ®I.X � C�� ��R������O¥�R�I.a�BbQJI.=�[:B�XjX�N�=�Kjª�B�X�B�FHQJK�IÇåÉB�X" I.X�a�B(C @�IP(I.abå"FHX�B×CO?���B�X�B�=]@>X�FH=�C�I.a =]N�azã�B�Xm[:B�=�B�X�FH@�I.X�KjFH=�C�@�I�P�©�B(P�¬E@�©�BWP(I.=TØ:B�X�[:B�=�P(BbI �@�©�B�a�B�@�©�I�C�¥M<>å�@�I2 7 å�B�X�P(B�=T@`I 0@�©�B>@¶d�å�?JP�FHQÉK�?Aa�N�QÃFH@�?JI.=�QJB�=�[8@�©kª�F.K`P(I.=�K�?JC�B�X�B(CÇF.Kt@�©�B=��B�&]N�?AQA?Aã�X�FH@�?JI.=k@�?Aa�B��OFH=�C�=�I.@t@�FH¬:B�=?A=T@�I F.P(P(I.N�=T@b?A=â@�©�BkF�Ø:B�X�FH[8?A=�[ å�X�I]P(B(CON�X�B(K�¥�e`©�?JK×P�FH=xã�B�@�©�I.N�[8©]@bI >F.KzN�K�?A=�[�QÃFHX�[:BA��K�F� ®B�@ d �Ûa�FHX�[8?A=ã�B(P�FHN�K�B«@�©�BmFH="FHQAd�K�?JK�I �@�©�BMB�Ø:I.QAN�@�?JI.=�I �@�©�B«ã�I���a�FH@�X�?>��P(I.abå�I.=�B�=T@�K5F.KtªtB�QAQ�F.K�@�©�B«å"FHX�@�?JP�QJB>å�I8K�?A@�?JI.=�KFH=�C�I.X�?JB�=T@�FH@�?JI.=�KcCO?JK�@�X�?Aã�N�@�?JI.=�KG?A=�CO?JP�FH@�B(C�@�©"FH@G@�©�BWB�&TN�?AQA?Aã�X�?AN�a ª�F.KGX�B�F.P�©�B(CA ®I.X � @�?Aa�B(K���ãTd�I.=�B×I.X�C�B�XI Za�FH[8=�?A@�N�C�BzK�a�FHQAQJB�X�¥

� � ��� ����� � �� � ��� ��� ��� � �������� � � �� ������� � ��� � ��� � � � ��� ����� ����� � � ��� � �

ÖuFHX�?JI.N�KÛK�@�X�N�P�@�N�X�B(K_I �@�©�B�å�B�=T@�FHa�B�X�KZFH=�Cc©�B�å�@�FHa�B�X�K_©"F(Ø:Btã�B(B�=$ ®I.N�=�Cz?A=zP(I.abå�N�@�B�XZK�?AazN�QÃFH@�?JI.=�K + �89 á� ;�8¶¥×e`©�BbK�?AazN�QÃFH@�?JI.=�Kzå�X�I�Ø:B(C @�©"FH@j?A= ã�I.@�©§P�F.K�B(KG@�©�B�X�B�B��O?JK�@G@�©�B '�N�?JC å�©"F.K�B�FH=�C K�I.a�BWK�I.QA?JC å�©"F.K�B(Kª5©�?JP�©�X�B�å�X�B(K�B�=]@�Ø8FHX�?JI.N�K�I.X�?JB�=T@�FH@�?JI.="FHQjI.X�C�B�X�?A=�[:K��5B8¥ [�¥ � FHQAa�I8K�@��� �X�B(BEX�I.@�FH@�?JI.=1�=�®K�@�X�I.=�[8QAd��b©�?A=�C�B�X�B(CX�I.@�FH@�?JI.=1�"FH=�C* ®X�I.\�B�=�X�I.@�FH@�?JI.= + � 60� � 4á � ;�8¶¥Se`©�BGQÃFH@�@�B�X«I.X�C�B�X�?A=�[�ª�F.K5I.ã�K�B�X�Ø:B(CEFH@5@�©�B>©�?A[8©�B(K�@«C�B�=�K�?A@�?JB(Kª5©�?JP�© FHX�Bb@�©�B�K�N�ãO¨vB(P�@zI `@�©�Bbå�X�B(K�B�=]@zª�I.X�¬ ?�FH@c@�©�B(K�B�C�B�=�K�?A@�?JB(Kc@�©�B�a�I.QJB(P�N�QJB(Kz?A=§ã�I.@�©xK�dOK�@�B�a�KcI.=�QAdØ�?Aã�X�FH@�BzFHX�I.N�=�C�@�©�B�?AX«QÃFH@�@�?JP(Bjå�I8K�?A@�?JI.=�KmFH=�CÇQA?Aã�X�FH@�B�FHX�I.N�=�C�@�©�B�?AX«å�X�B� B�X�X�B(CEI.X�?JB�=]@�FH@�?JI.=�K�¥

2 =z@�©�BuK�d�K�@�B�a�I �@�©�Buå�B�=T@�FHa�B�X�KSI.=�QAdcI.=�B�K�@�X�N�P�@�N�X�Btª5?A@�©�I.N�@Za�I.QJB(P�N�QÃFHXrX�I.@�FH@�?JI.=W©"F.KrãÉB(B�=) ®I.N�=�C%+ �89 �� 6 � � 4�8¶¥Se`©�?JKtK�@�X�N�P�@�N�X�BmP(I.=]@�FH?A=�K`@¶ª�I�å�B�=T@�FHa�B�X�K`?A=k?A@�K>½�µ�»�²Ê¼.°]Í.´�ºV¼8½�N�=�?A@`P(B�QAQ�FH=�C�?A@�K�[:B(I.a�B�@�X�d�FH@`P�QJI8K�Bå"F.P�¬�?A=�[§P�FH=ßãÉBÇK�B(B�=ß?A= p_?A[�¥ 6 F�?�K�B(BÇFHQJK�I e_FHã�QJB 2 ¥re`©�B � X�I�ª�K�@�X�N�P�@�N�X�B��rK�©�I�ª5= ?A= p_?A[�¥ 6 F�P(I.=�K�?JK�@�KbI X�I�ª«KWI MP�QJI8K�B�QAd å"F.P�¬:B(Cxå�B�=T@�FHa�B�X�K�¥�e`©�B�X�I%ª«KWFHX�B�å"FHX�FHQAQJB�Qt@�I�@�©�B k � F��O?JK��SFH=�C§@�©�B�a�I.QJB(P�N�QJB(KW?A=x@�©�BP(I.=�K�B(P�N�@�?AØ:BzX�I�ª«K>FHX�BcFH=]@�?>�Êå"FHX�FHQAQJB�Q_@�I�B�F.P�©�I.@�©�B�X�¥

2 =gP(I.=T@�X�F.K�@k@�Ißå�B�=T@�FHa�B�X�K��M@�©�B�©�B�å�@�FHa�B�X�K ®I.X�a � FH@�QJB�F.K�@��b@�©�X�B(B CO?���B�X�B�=T@ ��@�©�B�X�a�I]COd�="FHab?JP�FHQAQAdK�@�FHã�QJB�I.X�a�B�@�F.K�@�FHã�QJB��jK�@�X�N�P�@�N�X�B(Kzª5?A@�©�I.N�@�a�I.QJB(P�N�QÃFHXzX�I.@�FH@�?JI.= FH@c@�©�Bb©�?A[8©�B(K�@WC�B�=�K�?A@�?JB(K�+ ��� � � ;8¶¥�^>QAQ@�©�B(K�BkK�@�X�N�P�@�N�X�B(K���K�©�I�ª5= ?A= p_?A[�¥ 6 ã��¶C��tFHX�BkI >X�B(P�@�FH=�[8N�QÃFHXbN�=�?A@WP(B�QAQJK�¥ e`©�BÇK�@�X�N�P�@�N�X�B(K×?A= pr?A[�¥ 6 ãÉP�FHX�BK�?Aab?AQÃFHXG@�I�@�©�BWK�@�X�N�P�@�N�X�B) I.X�a�B(C�ãTd�@�©�B�å�B�=T@�FHa�B�X�K��0FH=�C�@�©�B�d�CO?���B�X: ®X�I.a B�F.P�©§I.@�©�B�Xmã]dE@�©�BWX�B�QÃFH@�?AØ:Bå�I8K�?A@�?JI.=�K�I >@�©�BEX�I�ª«K�¥qY>=�BEI m@�©�B�a �tC�B�=�I.@�B(C�ãTd h:�rª`F.K�I.ã�@�FH?A=�B(C ã]d F K�QJI%ª�P(I.abå�X�B(K�K�?JI.=qI G@�©�BK�dOK�@�B�a �X�I.a @�©�BkQJI�ª�B�X�C�B�=�K�?A@ d �uI.X�?JB�=T@�FH@�?JI.="FHQAQAd CO?JK�I.X�C�B�X�B(C��tå�©"F.K�BÇI >@�X�?ÃFH=�[8N�QÃFHXbQÃFH@�@�?JP(B8¥ße`©�BÇP�QJI8K�Bå"F.P�¬:B(CEØ:B�X�K�?JI.=EI r@�©�?JK5K�@�X�N�P�@�N�X�BcP�FH=�ãÉBGK�B(B�=�?A=�pr?A[�¥ 6 ã0¥ 2 @`?JK5?A=T@�B�X�B(K�@�?A=�[�@�I×=�I.@�?JP(BG@�©"FH@5@�©�BjK�@�X�N�P�@�N�X�Bh ?JK�=�I.@W@�©�B�a�I8K�@×C�B�=�K�BkK�@�X�N�P�@�N�X�Bkª5©�?JP�© P�FH=ßãÉBkI.ã�@�FH?A=�B(CßãTd§å"F.P�¬]?A=�[ X�I�ª«K×I M@�©�BkP�QJI8K�B�QAd§å"F.P�¬:B(C©�B�å�@�FHa�B�X�K�I M@�©�B�K�FHa�BkI.X�?JB�=]@�FH@�?JI.=qª5?A@�©�?A=�F�X�I�ª=�tK�B(B�erFHã�QJB 2 ¥ 2 = p_?A[�¥ 6 PÇI.=�BÇP�FH=qK�B(BÇF�K�@�X�N�P�@�N�X�B�� ®N�X�@�©�B�X�X�B� B�X�X�B(Ck@�IbF.K�^ �]ª5©�?JP�©Ç?JK�@�©�B>a�I8K�@`C�B�=�K�B>I _K�N�P�©ÇX�I�ª �¶K�@�X�N�P�@�N�X�B(K + � ;�8¶¥Se`©�BGK�@�X�N�P�@�N�X�B(K5^ FH=�C

2�2

Page 12: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

hq©"F�Ø:Bm@¶ªtIW©�B�å�@�FHa�B�X�K`?A=k@�©�BMN�=�?A@`P(B�QAQÊ¥uY>ãTØ�?JI.N�K�QAd ��FH@`C�B�=�K�?A@�?JB(K�©�?A[8©kB�=�I.N�[8© ��?Ê¥ B8¥Zª5©�B�=Ç@�©�B>å�X�B(K�K�N�X�B��s �]@�B�=�C�K`@�IW?A=OU�=�?A@¶d ���O@�©�B>K�@�X�N�P�@�N�X�Bj^ a�N�K�@`ãÉB>a�I.X�BGK�@�FHã�QJBm@�©"FH=�hm¥�e`©�BGK�@�X�N�P�@�N�X�BG^ ?JK���©�I�ª�B�Ø:B�X���=�I.@@�©�BWa�I8K�@cC�B�=�K�B×K�@�X�N�P�@�N�X�BbI �@�©�B�©�B�å�@�FHa�B�X�K%¥�LSØ:B�= a�I.X�BbC�B�=�K�BWK�@�X�N�P�@�N�X�BbI t@�©�BW©�B�å�@�FHa�B�X�K��� ®N�X�@�©�B�XX�B� B�X�X�B(C�@�IkF.KM@�©�B 3 K�@�X�N�P�@�N�X�B��É?JK>K�©�I�ª5=�?A=�pr?A[�¥ 6 C�¥«e`©�BWK�@�X�N�P�@�N�X�B 3 ?JK>@�©�Bza�I8K�@>C�B�=�K�BWK�@�X�N�P�@�N�X�BWI @�©�B�©�B�å�@�FHa�B�X�K>ª�BW¬]=�I%ª�FH=�C�?A@�KMN�=�?A@GP(B�QAQZP(I.=T@�FH?A=�K ®I.N�Xma�I.QJB(P�N�QJB(Kmª5©�?JP�©§FHX�B�=�[email protected]�?JB�=]@�B(C FHQJI.=�[k@�©�B©�I.X�?A\�I.=T@�FHQua�I.QJB(P�N�QÃFHX � X�I�ª«K��,�ÛK�B(B×e_FHã�QJB 2 ¥�Y>ã]Ø]?JI.N�K�QAd ��?A= @�©�B×QA?Aab?A@GI %s ��� @�©�?JKjK�@�X�N�P�@�N�X�B×azN�K�@jãÉBa�I.X�BcK�@�FHã�QJBc@�©"FH=E@�©�BjK�@�X�N�P�@�N�X�Bz^W¥

2 @m?JKcªtI.X�@�©x@�IE=�I.@�?JP(Bb@�©"FH@c=�I.=�B�I `@�©�B×QÃFH@�@�B�Xc@¶ª�I�K�@�X�N�P�@�N�X�B(K%�®^ÝFH=�C 3 �>ª�F.KzI.ã�@�FH?A=�B(CxãTd B�?A@�©�B�XF�K�åÉI.=]@�FH=�B(I.N�KM@�X�FH=�K�?A@�?JI.=A ®X�I.a�@�©�BzK�@�X�N�P�@�N�X�Bzh I.X«ã]dEP(I.abå�X�B(K�K�?A=�[�FH=TdEI.@�©�B�X>å�©"F.K�B8¥5e`©�?JK«?JKmC�B(K�å�?A@�B@�©"FH@��ʳ��zFH@GP�QJI8K�Bzå"F.P�¬]?A=�[�ã�I.@�©�@�©�B(K�BWK�@�X�N�P�@�N�X�B(KcFHX�B�C�B�=�K�B�XG@�©"FH= hsFH=�C � F.Km?A@GP�FH=�ã�BWK�B(B�=�?A= pr?A[�¥ 9 ��ʳ�³��W@�©�B�?AXW?A\�I.@�©�B�X�a�KbFHX�B�QJI�P�FH@�B(Cxã�B�QJI�ªÝ@�©�B�?JK�I.@�©�B�X�a P(I.X�X�B(K�å�I.=�CO?A=�[ @�IE@�©�B�QÃFH@�@�B�XWI.=�B�?A=â@�©�B�ª5©�I.QJBC�B�=�K�?A@ dkX�FH=�[:Bcª5©�B�X�Bj@�©�B�dEFHX�Bja�B(P�©"FH=�?JP�FHQAQAdEK�@�FHã�QJB8¥ue`©�?JK5?A=�CO?JP�FH@�B(KM@�©"FH@M@�©�BGQJI]P�FHQ0ab?A=�?Aa�F�I Z@�©�B: ®X�B(BB�=�B�X�[8d�P(I.X�X�B(K�å�I.=�CO?A=�[�@�Ib@�©�BcK�I.QA?JC�K�@�X�N�P�@�N�X�B(KMI Z©�B�å�@�FHa�B�X�K>FHX�BjØ:B�X�dÇC�B(B�å0¥ 2 =EP(I.=�K�B�&]N�B�=�P(B���@�©�Bj@�?Aa�B=�B(P(B(K�K�FHX�d I.XzI�P(P�N�X�X�B�=�P(BÇI «FH=]d§K�@�X�N�P�@�N�X�FHQ�@�X�FH=�K�?A@�?JI.=â?A=â@�©�B�©�B�å�@�FHa�B�XbK�dOK�@�B�a FH@�©�?A[8©âC�B�=�K�?A@�?JB(KW?JKazN�P�©�QJI.=�[:B�X5@�©"FH=Ç@�©�B>@�?Aa�B(K5I _@�©�BmK�?AazN�QÃFH@�?JI.=�K5å�B�X" ®I.X�a�B(C* I.Xt@�©�BGK�@�N�CO?JB(C�K�?A\�B(K�I _@�©�BmK�FHabå�QJB(K�¥Se`©�?JKFHQAQJI�ª«KMI.=�B: ®I.X5C�B�@�B�X�ab?A="FH@�?JI.=�I r@�©�BjB�QÃF.K�@�?JPmå�X�I.åÉB�X�@�?JB(K«I r@�©�BjK�@�N�CO?JB(C�K�@�X�N�P�@�N�X�B(K I.X«FWª5©�I.QJBGX�FH=�[:BjI ©�?A[8©�å�X�B(K�K�N�X�B(KmC�B(K�å�?A@�Bc@�©"FH@jFH@mF�X�FH=�C�I.abQAd�P�©�I8K�B�= å�X�B(K�K�N�X�Bc?A=�@�©�?JK>X�FH=�[:B�ªtB�¬]=�I%ªsª5?A@�©�å�X�I.ã"FHã�?AQA?A@¶dB�&]N"FHQ0@�I×N�=�?A@¶dÇ@�©"FH@MI.=�QAdÇI.=�BcI Z@�©�B(K�BcK�@�X�N�P�@�N�X�B(K«P�FH=�ãÉBG@�©�B�X�a�I�COd]="FHab?JP�FHQAQAdEK�@�FHã�QJB8¥

e`©�B�N�=�?A@kP(B�QAQGå"FHX�FHa�B�@�B�X�K�I z@�©�B�K�@�N�CO?JB(C K�I.QA?JC�KÇFH@kP�QJI8K�B�å"F.P�¬]?A=�[ ��?Ê¥ B8¥s?A=�@�©�B�QA?Aab?A@�I c?A=OU�=�?A@�Bå�X�B(K�K�N�X�B���FHX�BMP(I.QAQJB(P�@�B(C�?A=ke_FHã�QJB 2 ¥:e`©�BMP(I.X�X�B(K�åÉI.=�CO?A=�[�å"FHX�FHa�B�@�B�X�K5FH@tF: B�ª U�=�?A@�B«å�X�B(K�K�N�X�B(KtFHX�B«K�©�I%ª5=?A=Ee_FHã�QJB 2�2 ¥

��� � � � � �� � � ���� � � � ��� �

^mKZ?A@Sª�F.K�a�B�=]@�?JI.=�B(C�?A=�@�©�B`?A=]@�X�I]CON�P�@�?JI.=1��=�IjC�B� B(P�@�K�ª�B�X�B5å�X�B(K�B�=T@u?A=�@�©�B5K�@�X�N�P�@�N�X�B(KuK�@�N�CO?JB(Cb?A=b@�©�?JKªtI.X�¬�¥SiGB� ®B(P�@�KtFHX�B��T©�I%ªtB�Ø:B�X���N�="F(Ø:I.?JC�FHã�QJBGFH@uC�B�=�K�?A@�?JB(KuãÉB�QJI%ª�@�©�B«P�QJI8K�B«å"F.P�¬�?A=�[z?A=�@�©�BM@�©�B�X�a�I]COd�="FHab?JPQA?Aab?A@�¥ke`©TN�K��Û?A=§@�©�?JKzP(I.=]@�B���@��SF.Kjª�B�QAQ�F.Kj?A=§@�©�B�P(I.=T@�B��O@�I 5@�©�BbªtB�QAQt¬]=�I%ª5=§å�X�I.ã�QJB�a P(I.=�P(B�X�=�?A=�[�@�©�BQÃF.P�¬§I >FH=]d @�X�N�B�@�X�FH=�K�QÃFH@�?JI.="FHQ�I.X�C�B�X�?A=�[�?A=x@ ªtI CO?Aa�B�=�K�?JI.=�K%+ � 5���4 7 89�Û@�©�BkI.ã�@�FH?A=�B(CâB�QÃF.K�@�?JP�P(I.=�K�@�FH=]@�KFH=�CEP(I.abå�QA?ÃFH=�P(B(K>P�FH=EãÉBG@�©�I.N�[8©]@>I �F.K«C�B(K�P�X�?Aã�?A=�[�QJI]P�FHQ0B�QÃF.K�@�?JPcå�X�I.åÉB�X�@�?JB(K>I r@�©�BjK�@�N�CO?JB(C�K�d�K�@�B�a�K�¥

� � � � "z����������� �"�&��������2 =�e_FHã�QJB(K 2�2�2 �ÊÖ 2 @�©�B�CO?Aa�B�=�K�?JI.=�QJB(K�K�B�QÃF.K�@�?JP�P(I.abå�QA?ÃFH=�P(B(K�� ��5;:�NO. b � 5;:�NO.69 � <&Z21 �5I.ã�@�FH?A=�B(C I.X�@�©�B

å�B�=T@�FHa�B�X�KGFH=�CE@�©�Bj©�B�å�@�FHa�B�X�KGFHX�BcP(I.QAQJB(P�@�B(C�¥$��¦§BzC�Ib=�I.@>K�©�I�ªs@�©�BcP(I.abå�QA?ÃFH=�P(B(K�� ��������� R ��������� ª5©�?JP�©©"F(Ø:B�@�I>ãÉBt\�B�X�I>ãTdc@�©�B�K�d�aba�B�@�X�dcX�B�&TN�?AX�B�a�B�=]@�K�¥ � 2 @_P�FH=WãÉB�K�B(B�=W@�©"FH@_@�©�B�B�QÃF.K�@�?JP`P(I.abå�QA?ÃFH=�P(B(KSI.ã�@�FH?A=�B(C I.XZK�d�K�@�B�a�K�F.KSK�a�FHQAQ"F.K � C ���jå"FHX�@�?JP�QJB(K�CO?���B�XSã]dWI.=�QAd×F ®B�ª å�B�X�P(B�=T@3 ®X�I.a�@�©�B5B(K�@�?Aa�FH@�B(K�I.ã�@�FH?A=�B(C I.X@�©�Bc@�©�B�X�a�I�COd�="FHab?JP�QA?Aab?A@ � �� ¥5e`©�B�K�FHa�Bj?JKM@�X�N�B= ®I.X>@�©�BzwrI.?JK�K�I.=�X�FH@�?JI8KMª5©�?JP�©�P�FH=�ãÉB�I.ã�@�FH?A=�B(C

2 6

Page 13: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

®X�I.a @�©�BcP(I.abå�QA?ÃFH=�P(B(KMã]d �"2 7 ��¥2 @�?JK�ª�I.X�@�©k@�Iz=�I.@�?JP(B«@�©"FH@�@�©�B ��������� P(I.abå�QA?ÃFH=�P(B(K5FHX�BM=�B�[TFH@�?AØ:B I.Xu@�©�BMX�B(P�@�FH=�[8N�QÃFHX`K�@�X�N�P�@�N�X�BMI 0@�©�B

å�B�=T@�FHa�B�X�KjFH=�C�@�©�Bzh K�@�X�N�P�@�N�X�B�I S@�©�Bc©�B�å�@�FHa�B�X�K%¥MR]N�P�©�F�ãÉB�©"F�Ø]?JI.X>?JK«@ d]å�?JP�FHQ ®I.X>a�FH@�B�X�?ÃFHQJK>B��O?JK�@�?A=�[?A= ="FH@�N�X�B�FH=�C ?A@b?Aabå�QA?JB(Kb@�©"FH@�@�©�B�w_I.?JK�K�I.= X�FH@�?JI8K�I m@�©�B(K�B�K�@�X�N�P�@�N�X�B(K�FHX�BÇå�I8K�?A@�?AØ:B8¥ 2 = P(I.=]@�X�F.K�@�@�I@�©�B�a ��@�©�BzX�B�a�FH?A=�?A=�[ ��a�I.X�B�C�B�=�K�B��«K�@�X�N�P�@�N�X�B(KmI �@�©�B�©�B�å�@�FHa�B�X�KmB��O©�?Aã�?A@���·H±�³®²®³ �.µMP(I.abå�QA?ÃFH=�P(B(K ��������� �?Ê¥ B8¥>°Éµ Í:¼8²®³ �HµMw_I.?JK�K�I.=�X�FH@�?JI8K�¥�e`©TN�K���@�©�Bc^�FH=�C 3 K�@�X�N�P�@�N�X�B(K>FHX�BjØ:B�X�dEK�?Aabå�QJBcB���FHabå�QJB(K>I uFH=�?JK�I.@�X�I.å�?JPFHN���B�@�?JP>å�©"F.K�B(K�¥Se`©�BmåÉI8K�K�?Aã�?AQA?A@¶d�@�©"FH@5K�I.a�Bm=�I.=��¶P(I.=TØ:B��Ça�I.QJB(P�N�QJB(K`a�F(d� ®I.X�a�FHN���B�@�?JPmå�©"F.K�B(K�©"F.Ktã�B(B�=å�I.?A=T@�B(CEI.N�@«ã]d�I.=�BjI r@�©�BzFHN�@�©�I.X�KM?A=E@�©�BGå"F.K�@)+ 4�5�� ;.7 8¶¥

wZFHX�@cI t@�©�B×X�B(K�N�QA@�KGå�X�B(K�B�=]@�B(C ?A= @�FHã�QJB(K 2�2 �ÊÖ 2 ª�F.KcI.ã�@�FH?A=�B(C ã]d�N�K�?A=�[�F� B�ª�f>w ª�I.X�¬�K�@�FH@�?JI.=�K�¥ 2 @FHå�å�B�FHX�Kc@�©"FH@c@�©�B�K�?AazN�QÃFH@�?JI.=�K×I.=§@�©�B(K�Bbª�I.X�¬�K�@�FH@�?JI.=�KzP�FH=xã�BbK�å�B(B(C N�åxK�N�ã�K�@�FH=T@�?ÃFHQAQAd � FHQAa�I8K�@z@ ª5?JP(B��ª5©�B�=×@�©�B$��å�K�B�N�C�I<� X�FH=�C�I.a =TN�a�ãÉB�X�KtFHX�Bt[:B�=�B�X�FH@�B(C×ã]dzN�K�?A=�[G@�©�B«R�D>¦ Rz[:B�=�B�X�FH@�I.XSå�X�I.å�I8K�B(CWãTd�fmI.QA?ÃFH=µ�²m¼.º3+,2 687 8�ª5©�?JP�©â?JKjã"F.K�B(C I.=§@�©�Bb¦§B�d�Q�K�B�&]N�B�=�P(B8¥�e`©�?JKj[:B�=�B�X�FH@�I.X��_ª5©�?JP�©â?JKzFHQJK�IEP(I.=]Ø:B�=�?JB�=T@W@�IÇN�K�B I.Xcå"FHX�FHQAQJB�QtP(I.abå�N�@�FH@�?JI.=�K��r©"F.KzãÉB(B�=âFHQAX�B�F.COd @�B(K�@�B(CxãTd N�Kj?A=§@�©�B�P�F.K�B�I �X�B(B�B�=�B�X�[8d§P(I.abå�N�@�FH@�?JI.=�K I.X�@�©�B� v¥ P8¥ P8¥ FH=�Cß©0¥ P8¥ å0¥ P�X�d�K�@�FHQJKWI M©"FHX�CßK�å�©�B�X�B(K�+,2 6 2 8¶¥�n�I8K�@×I «@�©�BkX�N�=�KW?A=â@�©�B�å�X�B(K�B�=T@bK�?Aa�N�QÃF��@�?JI.=�KmI Z@�©�BWB�QÃF.K�@�?JP�P(I.=�K�@�FH=T@�Km©"F.K«ã�B(B�=�C�I.=�B�ãTd�N�K�?A=�[�@�©�BWR�D>¦ R�fmI.QA?ÃFH=1� KM[:B�=�B�X�FH@�I.XjFH=�CE?A@�KmK�?Aabå�QJBa�I�CO?VU"P�FH@�?JI.=�K +,2 686 8¶¥ 2 =�pr?A[�¥ 6 ��X�B�å�X�B(K�B�=]@�FH@�?AØ:B×B���FHabå�QJB(KmI S@�©�B�F.P(P�N�azN�QÃFH@�?JI.= å�QJI.@�KGFHX�BcK�©�I%ª5= I.X«@�©�BB�QÃF.K�@�?JP>P(I.abå�QA?ÃFH=�P(B(K`FH=�C�@�©�B k�� FH=�C ��k wrI.?JK�K�I.=kX�FH@�?JI8K�P�FHQJP�N�QÃFH@�B(C I.Xu@�©�BMX�B(P�@�FH=�[8N�QÃFHX`K�@�X�N�P�@�N�X�BMI 0@�©�Bå�B�=T@�FHa�B�X�K�ãTd�N�K�?A=�[z@¶ª�IWX�FH=�C�I.a =]N�azã�B�X�[:B�=�B�X�FH@�I.X�K���iGo>^>Dmi:6<;cFH=�C�@�©�BGR�DM¦ RbfmI.QA?ÃFH=1� K�[:B�=�B�X�FH@�I.X�¥2 @�P�FH=bãÉB5K�B(B�=�@�©"FH@S@�©�B5X�B(K�N�QA@�K�I.ã�@�FH?A=�B(C ®I.XSã�I.@�©b@�©�B5[:B�=�B�X�FH@�I.X�KtFH[8X�B(B«ª5?A@�©�?A=�@�©�B«B��OåÉB�X�?Aa�B�=]@�FHQ"B�X�X�I.X�¥e`©�?JK«B�=�P(I.N�X�FH[:B(KmI.=�Bj@�I×N�K�BG@�©�BcfmI.QA?ÃFH=1� KmR�D>¦ R�[:B�=�B�X�FH@�I.XM?A=EI.@�©�B�XMn�I.=T@�B 3 FHX�QJI�K�?AazN�QÃFH@�?JI.=�K�¥

l0I�I.¬]?A=�[ FH@Ç@�©�B�pr?A[�¥ 6 I.=�B�P�FH= FHQJK�IâB(K�@�?Aa�FH@�B�@�©�B P(I.=TØ:B�X�[:B�=�P(B I �@�©�B�P(I.abå�N�@�B(C C�FH@�FO¥�^mK�B����å�B(P�@�B(C + 6 � � 2 7 ;8�@�©�BÇP(I.=TØ:B�X�[:B�=�P(B�I «@�©�BkK�?AazN�QÃFH@�?JI.= X�B(K�N�QA@�KW?A=ß@�©�B�P�F.K�BkI «@�©�BkB�QÃF.K�@�?JP�å�X�I.å�B�X�@�?JB(K×?JKazN�P�©kK�QJI�ªtB�X�@�©"FH=1��B8¥ [�¥,�:?A=�@�©�BMP�F.K�BMI �@�©�B«B�&]N"FH@�?JI.=�I 0K�@�FH@�B8¥Se`©�B«K�QJI�ªgP(I.=]Ø:B�X�[:B�=�P(BGI �@�©�B '�N�P�@�N"FH@�?JI.=a�B�@�©�I�Cb?JK�FHQJK�IG?AQAQAN�K�@�X�FH@�B(Cb?A=�p_?A[�¥ � ª5©�B�X�BMI.=�B5P�FH=�K�B(B`@�©�B«F.P(P�N�azN�QÃFH@�?JI.=kå�QJI.@�K�I �@�©�B5B�QÃF.K�@�?JP5å�X�I.å�B�X�@�?JB(KI.ã�@�FH?A=�B(C I.X � C������×å�B�=T@�FHa�B�X�K ®I.XMFWX�N�=�P(I.=�K�?JK�@�B(CEI � � M � K ��jn 3 P�d�P�QJB(K%¥

2 @�?JKkªtB�QAQG¬�=�I�ª5= @�©"FH@Ç@�©�B�X�B�FHQG@�?Aa�B�I WK�?AazN�QÃFH@�?JI.=�K�N�K�?A=�[ FH=]dgP(I.abå�N�@�FH@�?JI.="FHQja�B�@�©�I�C P�FH= ãÉBX�B(CON�P(B(CE?> Z@�©�Bja�B�@�©�I�CEP�FH=Eã�BGå"FHX�FHQAQJB�QA?A\�B(C�¥`R]?A=�P(Bz@�©�Bjå�X�B(K�B�=]@«a�B�@�©�I]C�C�I]B(K«=�I.@«X�B�&TN�?AX�Bc@�Ib¬]=�I%ª @�©�BX�B� B�X�B�=�P(BmK�@�FH@�BMå�X�?JI.X�@�I�K�?AazN�QÃFH@�?JI.=�K5?A@`P�FH=�ã�B ®N�QAQAd�å"FHX�FHQAQJB�QA?A\�B(CEFH=�CkB�F.K�?AQAd�?Aabå�QJB�a�B�=]@�B(C�I.=ÇFzå"FHX�FHQAQJB�QP(I.abå�N�@�B�X�¥ 2 =§erFHã�QJB�Ö 2�2 ª�B�P(I.QAQJB(P�@�B(C§@�©�B�X�B(K�N�QA@�KcI.ã�@�FH?A=�B(C I.Xc@�©�B�B�QÃF.K�@�?JP�P(I.=�K�@�FH=T@�K= ®I.Xz@�©�X�B(BbX�N�=�KI u@�©�B×K�FHa�BWQJB�=�[8@�© � � K � n 3 P�dOP�QJB(K�� F� ®@�B�XjB�&TN�?AQA?Aã�X�FH@�?JI.=!��¥ze`©�BzU�X�K�@mX�N�= � F �Mª�F.Kmå�B�X" ®I.X�a�B(C ã]d�FK�?A=�[8QJB×å�X�I�P(B(K�K�I.XcK�@�FHX�@�?A=�[� ®X�I.a F�åÉB�X" B(P�@�QAd I.X�C�B�X�B(C X�B(P�@�FH=�[8N�QÃFHX�K�@�X�N�P�@�N�X�B�?_@�©�B×?A=�?A@�?ÃFHQ � � K ��×P�dOP�QJB(KªtB�X�BmK�å�B�=T@ ®I.X�B�&TN�?AQA?Aã�X�FH@�?JI.=0¥�e`©�B>I.@�©�B�Xt@ ªtI�X�N�=�Kuª�B�X�BMå�B�X" I.X�a�B(C�å"FHX�FHQAQJB�QAQAd�ã]d 2�4jå�X�I�P(B(K�K�I.X�K�¥ 2 =�@�©�BP�F.K�B)��ã!�_@�©�BMK�@�FHX�@�?A=�[zP(I.=OU�[8N�X�FH@�?JI.=�K`P(I.X�X�B(K�å�I.=�C�B(Cb@�Ij@�©�B«P(I.=OU�[8N�X�FH@�?JI.=�K�I.ã�@�FH?A=�B(C�ª5?A@�©�?A=�@�©�B5U�X�K�@�X�N�=F� ®@�B�X d � I�� j � K � n 3 P�d�P�QJB(Kuª5©�B�X�B � C K R � � � R K �z?JKS@�©�B5å�X�I�P(B(K�K�I.Xu=TN�azã�B�X�?�@�©�B«K�B�&]N�B�=�P(B(KuI �X�FH=�C�I.a=TN�a�ãÉB�X�K�ªtB�X�B�CO?���B�X�B�=]@z?A=§B�F.P�©âP�F.K�B8¥�D>I�B�&]N�?AQA?Aã�X�FH@�?JI.=âP�dOP�QJB(Kcª�B�X�BbåÉB�X" I.X�a�B(C§?A= @�©�?JK�P�F.K�B8¥ 2 = @�©�BP�F.K�B%�®P��«FHQAQr@�©�Bc?A=�?A@�?ÃFHQZP(I.=OU�[8N�X�FH@�?JI.=�KGªtB�X�B�@�©�BzK�FHa�BWF.KM@�©�Bz?A=�?A@�?ÃFHQrP(I.=OU�[8N�X�FH@�?JI.= ?A=�@�©�BWP�F.K�B%� F �`ã�N�@@�©�BmK�B�&TN�B�=�P(B(K�I Û@�©�BMX�FH=�C�I.aÝ=]N�azã�B�X�K`ªtB�X�BmCO?���B�X�B�=]@�? � � K � B�&]N�?AQA?Aã�X�FH@�?JI.=�P�d�P�QJB(KtªtB�X�Bmå�B�X" ®I.X�a�B(C�?A=

2 9

Page 14: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

B�F.P�©�I S@�©�B(K�BjX�N�=�K�¥ 2 @>P�FH=�ã�BcK�B(B�=E@�©"FH@>@�©�BcI.ã�@�FH?A=�B(C�X�B(K�N�QA@�K>FHX�Bj?A=�FH[8X�B(B�a�B�=]@Gª5?A@�©�?A=�@�©�BcP(I.a�ã�?A=�B(CK�@�FH@�?JK�@�?JP�FHQ_B�X�X�I.X�K�¥

� � � �"�&���������" �_�?$�$��"�& � " �?�������R�I.a�BÇå�X�I.å�B�X�@�?JB(K�I >@�©�Bk©"FHX�C��¶P(I.X�BEK�dOK�@�B�a�K���QA?A¬:BÇå�X�B(K�K�N�X�B�I.XbB�QÃF.K�@�?JP�P(I.=�K�@�FH=]@�K���FHX�B�CO?AØ:B�X�[:B�=]@�?A=

@�©�BbP�QJI8K�B��Êå"F.P�¬]?A=�[EQA?Aab?A@�¥bY>@�©�B�X=&]N"FH=T@�?A@�?JB(K���QA?A¬:BbP(I.abå�QA?ÃFH=�P(B(K��0@�B�=�C @�Ik\�B�X�IÇ?A= @�©�?JKGQA?Aab?A@�¥ 2 = [:B�=�B�X�FHQ �@�I�FH="FHQAd�\�B�=]N�a�B�X�?JP�FHQAQAd &TN"FH=]@�?A@�?JB(Kzª5©�?JP�©âCO?AØ:B�X�[:B�I.Xz@�B�=�C§@�I�\�B�X�I��_?A@c?JKja�B�FH=�?A=�[ ®N�Qu@�I�X�B(K�P�FHQJB�@�©�B�aãTd�@�©�B�?AXjF.K�d]abå�@�I.@�?JP(KGI.ã�@�FH?A=�B(C ®X�I.a F�@�©�B(I.X�B�@�?JP�FHQSX�B(K�B�FHX�P�©0¥ 2 =�@�©�Bzå"FHX�@�?JP�N�QÃFHXcP�F.K�BWI �@�©�BW©"FHX�C��¶P(I.X�BK�dOK�@�B�a�K`@�©�BzF.K�d�abå�@�I.@�?JP(K>FHX�BzI ��B�X�B(CÇã]dk@�©�B$ �X�B(BGØ:I.QAN�a�BzFHå�å�X�I���?Aa�FH@�?JI.= +,2 � � 6 4���2 689 á!2 6 5 8¶¥

e`©�B`B(K�K�B�=�P(B�I �@�©�B. ®X�B(BuØ:I.QAN�a�B«FHå�å�X�I:F.P�©�P(I.=�K�?JK�@�Kr?A=×@�©�B`I.ã�K�B�X�Ø.FH@�?JI.=×@�©"FH@S?A=W@�©�B5P(I.=�C�B�=�K�B(CWa�FH@�@�B�Xå�©"F.K�B(Kt@�©�BMa�I.QJB(P�N�QJB(K`P�FH=kãÉBM@�©�I.N�[8©T@5I _F.Kta�I�Ø�?A=�[�?A=ÇK�©�B�QAQJK ®I.X�a�B(C�ãTd�@�©�B�?AX�=�B�FHX�B(K�@�=�B�?A[8©Tã�I.X�K�¥Se`©�?JKFHå�å�X�I��O?Aa�FH@�?JI.= P�FH=�ãÉBGå�X�I%Ø:B�=�@�I×[8?AØ:BzF.K�d�abå�@�I.@�?JP�FHQAQAd�B���F.P�@MX�B(K�N�QA@�K I.X5@�©�BjB�&TN"FH@�?JI.=�I SK�@�FH@�BcI Z©"FHX�CK�å�©�B�X�B(K��®I.X«©"FHX�C�CO?JK�P(K���?A=�@�©�BzP�QJI8K�Bjå"F.P�¬]?A=�[kQA?Aab?A@ +,2 6 6 8¶¥ 2 @«?JKMªtB�QAQr¬]=�I%ª5=�@�©"FH@mFH@>©�?A[8©�C�B�=�K�?A@�?JB(K>@�©�BB�&]N"FH@�?JI.=âI «K�@�FH@�B�I «K�I.a�B�I.@�©�B�X�©"FHX�C��ÊãÉI�COd K�dOK�@�B�a�Kc?JKzFHQJK�IEªtB�QAQ`FHå�å�X�I��O?Aa�FH@�B(Cxã]d @�©�B� ®X�B(BbØ:I.QAN�a�B@�©�B(I.X�d + 689 � 2 6 ;��.2 987 8¶¥Çe`©�B �X�B(BbØ:I.QAN�a�B�å�X�B(CO?JP�@�K×FHQJK�IEP(I.X�X�B(P�@�QAd§@�©�B�F.K�d]abå�@�I.@�?JP ®I.X�a I `@�©�B�B�QÃF.K�@�?JPP(I.=�K�@�FH=]@�KzI t©"FHX�C K�å�©�B�X�B(KzFH=�C CO?JK�P(K(+ 9�� � 9 ;��16 � ��6<4�8¶¥ 2 @Gª5?AQAQSã�BWK�©�I�ª5=§ã�B�QJI�ª�@�©"FH@c@�©�B ®X�B(BWØ:I.QAN�a�BFHå�å�X�I��O?Aa�FH@�?JI.=�ªtI.X�¬OKMFHQJK�Ibª�B�QAQ0?A=�@�©�BcP�F.K�BjI Z@�©�BcK�@�N�CO?JB(C�å�©"F.K�B(K«I rå�B�=T@�FHa�B�X�KGFH=�CÇ©�B�å�@�FHa�B�X�K�¥

2 @M©"F.KmãÉB(B�= K�©�I%ª5= ?A=�+,2 6 6�8Z@�©"FH@: ®I.Xm@�©�B_U �¶CO?Aa�B�=�K�?JI.="FHQr©"FHX�C K�å�©�B�X�B(KGI u@�©�B×CO?ÃFHa�B�@�B�X 9ß@�©�B= ®X�B(BØ:I.QAN�a�B���� 8�� � < �T=�B�FHX5@�©�BmP�QJI8K�Bmå"F.P�¬�?A=�[b?JK�å�X�I.åÉI.X�@�?JI.="FHQ�@�IW@�©�B�� �Ê@�©�åÉI%ªtB�X)����ã�B�?A=�[×@�©�B>=]N�azã�B�X«I Û@�©�Ba�I.QJB(P�N�QÃFHXzC�B�[8X�B(B(KcI . �X�B(B(C�I.a �0?Ê¥ B8¥���C M I.XG©"FHX�C CO?JK�P(KcFH=�C���C �� I.Xj©"FHX�C K�å�©�B�X�B(K��>I t@�©�BbB���P(B(K�KCO?JK�@�FH=�P(B��)u C m 93��ã�B�@¶ª�B(B�=x@�©�BbP(B�=]@�B�X�KcI t@�©�B×=�B�?A[8©]ãÉI.X�?A=�[�K�å�©�B�X�B(KcFH@j@�©�B�?AXjQÃFH@�@�?JP(B�K�?A@�BWå�I8K�?A@�?JI.=�K��ª5©�?JP�© FHX�BjCO?JK�@�FH=�P(B(CEã]d��� +,2 6 6�8

�8�� � < C� d u&j�� R � 6�� �

ª5©�B�X�B

u�<�9 b u � C d > <?> 7 |#j ­�� D m K R � 6 4 �

> ?JK«@�©�BjØ:I.QAN�a�B�I r@�©�B�K�dOK�@�B�a �'> 7 |b?JK5@�©�BjØ:I.QAN�a�B�I Z@�©�BzP(I.=�K�?JC�B�X�B(C�K�@�X�N�P�@�N�X�BWFH@MP�QJI8K�Bjå"F.P�¬]?A=�[ ��FH=�C zC�B�å�B�=�C�KGI.=�@�©�BWK�©"FHå�BzI �@�©�B) �X�B(B�Ø:I.QAN�a�B8¥m^Må�å�QAd�?A=�[�@�©�?JK I.X�azN�QÃF�@�IÇFH=�?JK�I.@�X�I.å�?JPz©"FHX�C�ã�I]CO?JB(KGFH=�CF.K�K�N�ab?A=�[�@�©"FH@M=�B�FHXmP�QJI8K�Bcå"F.P�¬]?A=�[� cC�I]B(KM=�I.@>C�B�å�B�=�C�I.=�@�©�BcØ:I.QAN�a�Bcå�B�XMå"FHX�@�?JP�QJB%��ª5©"FH@>a�B�FH=�K>@�©"FH@@�©�B) �X�B(BzØ:I.QAN�a�BWC�I�B(K>=�I.@mP�©"FH=�[:B�?A@�KmK�©"FHå�Bzª5©�B�=�@�©�B�Ø:I.QAN�a�B�I �@�©�BWK�dOK�@�B�a�?JKmP�©"FH=�[:B(C ã]d�?JK�I.@�X�I.å�?JPå�X�B(K�K�N�X�B��rI.=�B5P�FH=b=�B�[8QJB(P�@S@�©�B5P(I.=�K�@�FH=T@� `FH=�Cת5X�?A@�B`@�©�B5P(I.=OU�[8N�X�FH@�?JI.="FHQ ®X�B(B5B�=�B�X�[8dzå�B�X�I.=�B � a�I.QJB(P�N�QJB����ã�I]COd �t?A=�@�©�B I.X�a �

� 8�� � < C m Z21 ����� 8�� � < C m ��Z21 ��� � d >J<?> 7 |�j ­�� D m K � � � 6:; �

2 6

Page 15: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

e`©�?JK5QJB�F.C�KM@�I×@�©�B ®I.QAQJI%ª5?A=�[�B�&]N"FH@�?JI.=�K I.X5@�©�BGå�X�B(K�K�N�X�BzFH=�CE@�©�BGã�N�QA¬ka�I�CON�QAN�K �

s 8�� � < C m f �f%d >J< � j C �2� Z21

U > . K I Ku � 3 � 6 ; �

v 8�� � <� C m > f sf > C K < � 8�� � <� C

C �2� Z21U >

�K I K I ­

Du � I ­Dd u � j ��� R � 6 5 �

ª5©�B�X�B�u � ?JK5C�B�U�=�B(CE?A= � 6 4 ��¥^mK�?A@Ç?JKÇB�F.K�dg@�IßK�B(B��«@�©�B�å�X�B(K�K�N�X�B K�©�I%ª«K�K�?A=�[8N�QÃFHX�?A@¶d I z@�©�BA I.X�a d u � j ­ ª5©�B�X�B�F.K�@�©�B�QJB�F.CO?A=�[

K�?A=�[8N�QÃFHX�?A@ d�I �@�©�B�ã�N�QA¬�a�I]CON�QAN�Km?JKmI u@�©�B= I.X�a d u � j � ¥>e`©�B�B�QÃF.K�@�?JPWP(I.=�K�@�FH=]@�KGFHX�BWB��OåÉB(P�@�B(C�@�I�K�©�I�ª@�©�BcK�FHa�B ��QJB�F.CO?A=�[7�«K�?A=�[8N�QÃFHX�?A@¶dEF.K5@�©�Bcã�N�QA¬�a�I�CON�QAN�K)+ 9�� 8¶¥

2 =c@�©�Bupr?A[�¥ 45ª�BuK�©�I%ªx@�©"FH@_@�©�B3 ®X�B(BSØ:I.QAN�a�B�FHå�å�X�I���?Aa�FH@�?JI.=ת�I.X�¬�K_ªtB�QAQ]ãÉI.@�©�?A=z@�©�B�P�F.K�BtI �åÉB�=]@�FHa�B�X�KFH=�Cß©�B�å�@�FHa�B�X�K( I.X�ª5©�?JP�© U C M FH=�C � C �O¥ 2 @WP�FH= ã�BÇK�B(B�= @�©�B�X�Bk@�©"FH@b@�©�B�X�FH@�?JI8K�I M@�©�B�B�QÃF.K�@�?JPP(I.=�K�@�FH=]@�Ku@�Iz@�©�B5ã�N�QA¬×a�I]CON�QAN�K�I.ã�@�FH?A=�B(C( ®X�I.a @�©�B ®X�B(B«Ø:I.QAN�a�BmFHå�å�X�I��O?Aa�FH@�?JI.=ÇFHX�BMªtB�QAQ�FHå�å�X�I��O?Aa�FH@�B(CãTd�QA?A=�B�FHX. ®N�=�P�@�?JI.=�K5I 0@�©�Bm?A=TØ:B�X�K�BGC�B�=�K�?A@ d:¥ 2 =�å"FHX�@�?JP�N�QÃFHX���F.K�å�X�B(CO?JP�@�B(CÇãTd�@�©�B ®X�B(BMØ:I.QAN�a�Bm@�©�B(I.X�d �O@�©�BX�FH@�?JI8K s�<=s 8�� � < FH=�C v �-<�v 8�� � <� @�B�=�CE@�I�N�=�?A@¶d�FH@>P�QJI8K�Bcå"F.P�¬�?A=�[�¥ 2 =E@�©�BjU�X�K�@>P�F.K�Bz@�©�B�F.P(P�N�X�F.P�d�I S@�©�BB��OåÉB�X�?Aa�B�=]@�FHQZC�B�@�B�X�ab?A="FH@�?JI.=§I t@�©�?JKMQA?Aab?A@G?JK>azN�P�© ©�?A[8©�B�X(�®P�QJI8K�B�@�I�I.=�B�å�X�I.ab?AQJB��M@�©"FH= ?A=�@�©�BWK�B(P(I.=�CP�F.K�B � FHã�I.N�@«@¶ª�I�å�B�X�P(B�=T@���¥

e`©�B�I.X�CO?A="FH@�B(KkI m@�©�B ��QA?A=�B�FHX��×U�@�K�K�©�I�ª5=�?A=�pr?A[�¥ 4 FH@�Ø:I.QAN�a�B(K�P(I.X�X�B(K�å�I.=�CO?A=�[§@�I§P�QJI8K�BÇå"F.P�¬�?A=�[:KI `@�©�B�K�@�N�CO?JB(C§K�@�X�N�P�@�N�X�B(K�P�©"FHX�F.P�@�B�X�?A\�B%&TN"FH=]@�?A@�FH@�?AØ:B�QAd @�©�BbK�?A=�[8N�QÃFHXzã�B�©"F(Ø�?JI.Xc?A= @�©�BbØ�?JP�?A=�?A@¶d I 5P�QJI8K�Bå"F.P�¬�?A=�[:K�I �K�@�N�CO?JB(CbK�@�X�N�P�@�N�X�B(K�¥Ze`©�B5I.ã�@�FH?A=�B(C�P(I�B�@�P�?JB�=T@�KuFH=�CbCO?AX�B(P�@�?JI.="FHQ�w_I.?JK�K�I.=bX�FH@�?JI8KuFHX�B5P(I.QAQJB(P�@�B(C?A=Ee_FHã�QJBzÖ 2�2�2 ¥ 2 @«P�FH=EãÉBjK�B(B�=�@�©"FH@MK�I.a�BjI Z@�©�BjØ.FHQAN�B(KMI ZCO?AX�B(P�@�?JI.="FHQrw_I.?JK�K�I.=EX�FH@�?JI8K>FHX�Bj=�B�[TFH@�?AØ:B8¥

� � ��� ����� � � � ��� � �� � ����� �� �

LSQÃF.K�@�?JP�å�X�I.å�B�X�@�?JB(KWI mC�B�=�K�B�K�I.QA?JCâK�@�X�N�P�@�N�X�B(K I.X�å�B�=T@�FHa�B�X�K�FH=�Câ©�B�å�@�FHa�B�X�KתtB�X�BkC�B�@�B�X�ab?A=�B(C ãTdFH="FHQAdOK�?JKZI "@�©�Buã�I���a�FH@�X�?>�WB�Ø:I.QAN�@�?JI.=×?A=Wn�I.=T@�B 3 FHX�QJIGK�?Aa�N�QÃFH@�?JI.=�K�¥ 2 @r©"F.KrãÉB(B�=×K�©�I�ª5=×@�©"FH@SK�?Aa�N�QÃFH@�?JI.=�KI mK�d�K�@�B�a�K�F.KbK�a�FHQAQMF.K � C ����[8?AØ:B�X�B(K�N�QA@�Kת5©�?JP�©gCO?���B�Xbã]dâI.=�QAd FA ®B�ª å�B�X�P(B�=T@( ®X�I.a�@�©�BÇX�B(K�N�QA@�KI.ã�@�FH?A=�B(CEã]dkB��O@�X�FHå�I.QÃFH@�?JI.=�@�I×@�©�Bj@�©�B�X�a�I�COd]="FHab?JPzQA?Aab?A@�¥

e`©�B�F.K�d]abå�@�I.@�?JP(KÇI j@�©�B�I.ã�@�FH?A=�B(C�B�&]N"FH@�?JI.=�I zK�@�FH@�B��`ã�N�QA¬ a�I�CON�QAN�K��MFH=�CgB�QÃF.K�@�?JP�P(I.=�K�@�FH=T@�K�FHX�B?A=qFH[8X�B(B�a�B�=T@bª5?A@�© å�X�B(CO?JP�@�?JI.=�K�I mF�K�?Aabå�QJBkØ:B�X�K�?JI.= I M@�©�B* ®X�B(B�Ø:I.QAN�a�BÇ@�©�B(I.X�d:¥xe`©�BkP(I�B�@�P�?JB�=T@�K�I @�©�B�QJB�F.CO?A=�[ÇK�?A=�[8N�QÃFHX�?A@�?JB(KjI �å�X�B(K�K�N�X�B×FH=�C�B�QÃF.K�@�?JP×P(I.=�K�@�FH=]@�Km?A=�@�©�B�Ø]?JP�?A=�?A@ d�I �@�©�BWP�QJI8K�B�å"F.P�¬�?A=�[k©"F�Ø:Bã�B(B�= C�B�@�B�X�ab?A=�B(C�¥ e`©�B(K�B P(I]B�@�P�?JB�=]@�KEP�FH= ãÉB�N�K�B� ®N�Qm@�IßP(I.=�K�@�X�N�P�@�FH=�Cg@�Iß@�B(K�@ÇØ8FHX�?JI.N�KÇ@�©�B(I.X�B�@�?JP�FHQFHå�å�X�I��O?Aa�FH@�?JI.=�KmP(I.=�P(B�X�=�?A=�[�B�QÃF.K�@�?JP�?A@ dEI ra�I.QJB(P�N�QÃFHXMK�d�K�@�B�a�K%¥

¦§B�K�©�I.N�QJC�=�I.@�B�@�©"FH@�@�©�B�P(I.abå�N�@�FH@�?JI.=�KÇåÉB�X" I.X�a�B(C�K�©�I�ª @�©"FH@�@�©�B�wrI.?JK�K�I.=�X�FH@�?JI8K�I c@�©�B�a�I8K�@C�B�=�K�B�K�@�X�N�P�@�N�X�B(K×I «©�B�å�@�FHa�B�X�K×FHX�B�=�B�[TFH@�?AØ:B8¥�e`©�?JK�X�B(K�N�QA@×P(I.=OU�X�a�K×B�FHX�QA?JB�XWK�N�[8[:B(K�@�?JI.=�Kz@�©"FH@×P(B�X�@�FH?A=

2 �

Page 16: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

=�I.=��¶P(I.=TØ:B��Ea�I.QJB(P�N�QJB(KMa�F(d% I.X�a�å�©"F.K�B(K«I �FH=�I.a�FHQJI.N�KMwrI.?JK�K�I.=EX�FH@�?JI + ;.7 8¶¥Z¦§BcK�©�I.N�QJC�K�@�X�B(K�K5@�©"FH@«@�©�B©�B�å�@�FHa�B�X�KZFHX�BS=�I.@_FH=zB���P(B�å�@�?JI.=z?A=c@�©�?JKrF.K�å�B(P�@�?.FH="FHQAd�@�?JP�FHQ�FH=�CzP(I.abå�N�@�B�X_K�?Aa�N�QÃFH@�?JI.=�X�B(K�N�QA@�K_P(I.=�P(B�X�=�?A=�[I.@�©�B�X«a�I.QJB(P�N�QJB(K ®I.X�ab?A=�[�²�¿�µ�½�Æ�·�Å8ÀH°É¼.Æ׳®»�¼8º#ºÂÀ�±�²Ê¼TÜ�ºJµ«FHN���B�@�?JPjå�©"F.K�B(K5ª5?AQAQ0ã�BjCO?JK�P�N�K�K�B(C�B�QJK�B�ª5©�B�X�B8¥

2 @«?JK«ª�I.X�@�©�@�IkF.C�CE@�©"FH@m@�©�BzK�?Aa�N�QÃFH@�?JI.=�a�B�@�©�I�C�FHå�å�QA?JB(C�?A=�@�©�?JK>å"FHåÉB�XmC�I]B(KM=�I.@>X�B�&]N�?AX�BcN�K�?A=�[�@�©�BK�@�X�N�P�@�N�X�FHQ�å"FHX�FHa�B�@�B�X�K:��X�B� B�X�B�=�P(BMK�@�FH@�B��SI É@�©�B5N�=�?A@tP(B�QAQ�I �@�©�B«K�@�N�CO?JB(C�K�dOK�@�B�a F.KtFH=�K�?AazN�QÃFH@�?JI.=�?A=�å�N�@�¥e`©�B>X�B� ®B�X�B�=�P(B(�®B�&]N�?AQA?Aã�X�?AN�a*��K�@�FH@�BM?JK�C�B�@�B�X�ab?A=�B(CǪ5?A@�©�?A=k@�©�BmK�FHa�BMX�N�=k?A=�ª5©�?JP�©Ç@�©�B>B�QÃF.K�@�?JPmå�X�I.å�B�X�@�?JB(KFHX�BbC�B�@�B�X�ab?A=�B(C�¥�e`©�?JKjK�F�Ø:B(KzFÇK�N�ã�K�@�FH=]@�?ÃFHQtFHa�I.N�=T@�I �@�©�BbK�?Aa�N�QÃFH@�?JI.=§@�?Aa�B8¥be`©�?JKzFHQJK�I�FHQAQJI%ª«KzI.=�B×@�I?A=�P�X�B�F.K�BM@�©�BMF.P(P�N�X�F.P�d�I É@�©�BMX�B(K�N�QA@�K�ã]dbB���@�B�=�CO?A=�[�@�©�B5QJB�=�[8@�©�I �@�©�B«K�?Aa�N�QÃFH@�?JI.=�KtK�?Aabå�QAdWã]d�P(I.=T@�?A=]N�?A=�[@�©�B�a ®X�I.a @�©�Bjå�QÃF.P(Bj?A=Eª5©�?JP�©E@�©�B�dǪtB�X�BcK�@�I.å�åÉB(C�¥

^>QA@�©�I.N�[8© @�©�B×FHå�å�QA?JB(C§a�B�@�©�I]C I `B�QÃF.K�@�?JPWå�X�I.åÉB�X�@�?JB(KcC�B�@�B�X�ab?A="FH@�?JI.=ßC�I]B(Km=�I.@cP(I.=]Ø:B�X�[:B�F.K$&TN�?JP�¬]QAdF.K>a�B�@�©�I]C�KmN�K�?A=�[ÇI.@�©�B�X>@�©�B�X�a�I�COd�="FHab?JPWB�=�K�B�azã�QJB(K(�®B8¥ [�¥M@�©�B%� > 1�B�=�K�B�azã�QJB�����?A@�KmK�?Aabå�QA?JP�?A@ d ��@�©�B�X�B?JKc=�IE=�B(B(C @�I�FHå�å�QAd ab?JP�X�I8K�P(I.å�?JP�B���å�X�B(K�K�?JI.=�K$ I.Xc@�©�Bbå�X�B(K�K�N�X�B�I.Xc?A@�KzC�B�X�?AØ8FH@�?AØ:B(K��jFH=�CxåÉI8K�K�?Aã�?AQA?A@¶d @�IP�FHQJP�N�QÃFH@�B�¼.º�ºT@�©�BjB�QÃF.K�@�?JPmP(I.=�K�@�FH=T@�K«?A=EF�±�³#°]Í8ºAµtX�N�=EB�=�P(I.N�X�FH[:B(K«I.=�B: I.X«FHå�å�QAd]?A=�[�?A@�?A=�Ø8FHX�?JI.N�K5K�dOK�@�B�a�K�¥2 =ßå"FHX�@�?JP�N�QÃFHX���@�©�?JK×a�B�@�©�I�C K�B(B�a�Kb@�I�ã�BÇå�X�B� ®B�X�FHã�QJBÇ?A=qK�?A@�N"FH@�?JI.=�K�ª5©�B�X�B�I.=�BÇ=�B(B(C�K�B�F.K�dßFH=�C &]N�?JP�¬B(K�@�?Aa�FH@�B(K5I Û@�©�BGB�QÃF.K�@�?JPmå�X�I.å�B�X�@�?JB(K I.X�K�dOK�@�B�a�K�ª5?A@�©�P(I.abå�QJB�� �®B8¥ [�¥Sa�I.QJB(P�N�QÃFHX��t?A=]@�B�X�F.P�@�?JI.=�K I.Xtª5©�?JP�©P�FHQJP�N�QÃFH@�?JI.=�K×I �@�©�B ®I.X�P(B(KWFHX�B�B�?A@�©�B�Xz@�?Aa�B��¶P(I.=�K�N�ab?A=�[ I.Xz=�I.=T@�X�?AØ�?ÃFHQÊ¥�e`©�?JKc?JK��_B8¥ [�¥,�Û@�©�B�P�F.K�B�I «K�I.a�BK�dOK�@�B�a�K I.X�ab?A=�[�?JK�I.@�X�I.å�?JP�FHN���B�@�?JPjå�©"F.K�B(K«ª5©�?JP�©�FHX�Bj@�©�BzK�N�ãO¨vB(P�@«I SK�B�å"FHX�FH@�Bjª�I.X�¬�K%¥

� �� ����� ��&� "����^���¦§BbFHX�BW[8X�FH@�B� �N�QS@�I�imX�¥chG¥�l�¥�fmI.QA?ÃFH=A I.XjK�B�=�CO?A=�[�@�IkN�KG@�©�BbP(I]C�B×I �@�©�BbR�D>¦ R ��å�K�B�N�C�I<� X�FH=�C�I.a

=TN�a�ãÉB�X�[:B�=�B�X�FH@�I.X�FH@W@�©�BÇØ:B�X�dâãÉB�[8?A=�=�?A=�[§K�@�FH[:BkI m@�©�?JK×å�X�IH¨vB(P�@�¥âwrFHX�@�I m@�©�?JKתtI.X�¬âª�F.K�K�N�å�å�I.X�@�B(CãTdâ@�©�B�[8X�FH=]@(6:e$2�2(p 7 2 7 689 I >@�©�Bkw_I.QA?JK�© 3 I.abab?A@�@�B(B% ®I.X�R�P�?JB�=T@�?VU"P�o>B(K�B�FHX�P�© �®¤jh`D ��¥ZwZFHX�@�I M@�©�BP�FHQJP�N�QÃFH@�?JI.=�K>ª�F.K5å�B�X" ®I.X�a�B(C�FH@«@�©�BcwrI.\(="F�� 3 I.abå�N�@�B�XmFH=�C�DmB�@¶ª�I.X�¬]?A=�[ 3 B�=T@�B�X��®w 3 R�R���¥

� �&�i���O�&��Q�&������� ���������������������� �!#"$�#%���&' �()%+*, .-'/.�)02131��546��72137�89 � :;�<= �>? )�#&�@����A�2�?&CBD )EA )FG��*���H#�I*��3J�K���L�J�M�� �N��O� '/�P.Q �)03R27�46��7�S�:�89 � 02�<= �>? )�#&�@�������FT ?UV )W�X�X;O�����������&YBD �E� �FZ�2*[��H#��*[��J�K���L�J�M��� �N#�O� )�\�+K]K� /./?��:21��^46��7�S�0�89 � 1��_` ?>? )<a�����?�2@,��L���X�%���&)*��)���bX2cdN#X;M3��@'(�X�%*��K6MeX2cf� X3��&�X��Y�$P?g?h\��:2737C4]��7�S3038+ � R;CFT ?UV �WAX�X;O���#����&Yia )Wj �N#������>? ?kaJ)�lY )LmJ�M��� �n�o �)03S�p�7�46��7�S3q389 � S2Y(� .kb�����3*�@[@,�)>� )�Ar)r)@[*���&CLmJ�M���*[%��#n.s\�?:�t2:3te46��7�t2:389 �utv�>? )wA*[�*[@�@x�2�y&�z{<|�2�IX�� ��>� ?kaJ��lY )L�J�M�� �-�}\��1�t�:27�46��7�t2:389 � q2CLf �L�*����I��~�����*,�3>? 3��������%y��*��3FT ��D�?%+�M�~�����*����2��&^�5 �FT �FGX2�]%*���%yJ)X;H�����*,��LmJ)*�@[X3��X�r�J)*[%��2@����2�3���*[�)�A��s�Q �?��p�t

46��7�q3p389

2�4

Page 17: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

� 72CLf �L�*[��y�2~?�]��*,�)>� )� ��� ��%y��*��)����&C�5 �FT �F X��]%+*[��%yJ)X;H�����*���� X3@���%+�)@x�2�|L�J�M��]*x%�An.h\��:�:3R 4]��7�q���8+ �[��p2C� �k� �<b�I��~)�;�)��Lf �L�*[��y�2~�����*��)����&��5 �FT )F X��]%+*[��%yJ)X;H�����*���>? )L�J�M�� ?kaJ��l5*[�]K��IMeX�cd(�X3@�*x&)�#n�s �)q��vt 46��7�q�0�89 �[���C� ?<aX3�)*x�������K���Lf )Lm*����I��~��]��*,�)�2��&�Lf )L�*[��y�2~?�]��*,��L�J)*[@�X��]X3r)J)*x%�2@ ���2�3���*[�)�D�$-�h\��R3tC46��7�q�1�89 �[��:;C_` ?i)�I������@'����&Y<� )� �� �)@x&������� X3@���%2 �L�J�M��� ?-?- � ���;t��V46��73q3R389 �[��02C� .(�K��IX�X � ���3Ky��)Wj �! �FT �� �����3��I�������3����3�2�?&C_` �i)�I������@,��L�J�M�� ?N#�O� )� �K]K� .-?Q � ��1�R�: 46��7�q�S�89 �[�1�C� ?(' )F ���]KIJ)�*[lY��>? ?kaJ)�lY )L�J�M��� ?g.Q �?t;0�:20�46��7�q�t�89������ �2@x�]X5�I�+c���������%+���mKIJ)��I�*[� �[��R;C�5 )FT )FGX2�]%*���%yJ)X;H�����*,��L�J�M�� )�\�+K]K� �� /)P?P �)0�t3te4]��7�q�t28+ �[��S2CBD �<bX�� � @�*[���)� X�@[��%� �L�J�M�� ?}.g\�'��7)�546��7�q37389�)���� ��@[��X`�I�+c���������%+���bK�J)������*��\ �[�vtvC�5 )FT )FGX2�]%*���%yJ)X;H�����*,��_j ?i)�I��)�3�@,�)�2��&�� .k� ?<a�y�2~��v����L�J�M��� �N#��O� )� �+K�K� ?}.}\�)0)��S3qC4]��737)��8+ �[��q2C_` �i������)����@���*[����������� ��������������������� ���! #"$��%'&(�)����*$��� �+�,�� -��./������&�*�K���& � M >� �Lf 'WA�����]��� �'_j '�\�O�����0��)�3�.����&

>? �1.*[�)��z{>����]K�*[�Z4�E�@x�]��O�*������ ��7�7���89 �[��72C�5 )FT )FGX2�]%*���%yJ)X;H�����*,��>� ?kaJ��lY )L�J�M�� �o?n �)13p37�7 4]��737)��8+ �u:2p2�UV �BD )EmOv��������� X�@[��%� �L�J�M�� ?Q.Q'�?7�S�7�46��7�7�:�89 �u:��C>? �� .k� �wd����Il^�2� �2��&�_` �i)�I��)�3�@,��L�J�M�� �N��O� )�Tn�- ��R2S303:C46��7�73:389 �u:�:;Yk� )wd���3�)��EA �� )Lf ?Lf���I�3�������& Lf ��j �� X3���]X3� �)>? ?kaJ)�lY )L�J�M��� ?o?}\�)7�p3S�p�46��7�73:389 �u:202C�5 )FT )FGX2�]%*���%yJ)X;H�����*,��L�J�M�� )N#��O� �< n�} ��:�S�4]��7373:�8+ �u:;1�C� �Lf '��@[@���� �\UV .BD �E�O;������'_` 'i)�I��)�3�@,������& <= �� '� �)@x&�����'�#&�O;�2��%��& kaJ)��l5*[%��2@ L�J�M���*x%� 324252 ��� �d�

46��7�730389�)����&C���c���I���%���aK�J)������*��\ �u:�R;C� �L .� �2@x�2��X3����*'����& Lf ��j �� X3���]X3� �)>? .kaJ)�lY �L�J�M��� /�h�Q �)S�q�737C4]��737�t28+ �u:2S2C� ?()%yJ)l5*[&�KA����&YW ��76�Hb�� ��L�J�M��� �N#�O� )E�-.-'�?t�:�:�qC4]��7�7�t28+ �u:3tvCN �<b@x����� �2��&�<= )� �� ��@[&�������L�J�M��� )N#��O. �E -?g\��R2q�t20C4]��737�q38+ �u:2q2 Lf +89 ?k� �B �*:9��*[�I���)� �>? )� �3�6KI��y����2�?&�<= )� ?� �)@x&������� X3@���%2 ?ka�IM��� �� *;0��)*[& ka�IM�� �s�P�s\�'��S�te4]��737�q38+ �u:272C�5 #FT #FGX2�]%+*[��%yJ�X;H��]��*,�A*[�=<� >�/ -�;�, ?��@��/&BAC"�D)�,��@�EGF�HI$���,��JK��L �����*M"$��./�,���,���N� �M�GO�./JPIM� >���Q<L��JR�&:� ?��. �+�y�

��&)* KI��& � MC� �B X����)M��2l^�j����&!89 ?��r)r.��)J)��*�l 4�FGX��I@[& (�%*�����K�*:S?%2�?(�*��)���2r.X��I������737�q�89��r �S37) � 0�p2CN �<b�I�)*[���]l^����L�J�M��� �N#��O� �E }.s\�)p�S)�;t;p�Re4�:�p�p���89 � 0)�Yk� )wd���3�5�2��&��� �k� �� ��%�_AX;Hb�@[@,��>? ?kaJ)��l� �L�J�M��� /./�n �'��p�1��3�`4�:�p�p���89 � 03:;C� ��j �<|�;KI�����)� ?UV �!AX��IX����2��&Y_` �i)�I������@,�)>? ?kaJ)�lY )L�J�M��� /?/�}\�)t�:��;te4,:2p�p�:�8+ � 0�02Yk� �� %�<b��*x&�� �2��& k� )wd���3�)�)>? ?kaJ)��l� �L�J�M��� /./�}\�'�vt�R3te4�:2p3p3:389 � 021�C>? �_A��� � *[�@[@[���.k� )! ?� *[��X3���)�2�?&CWj ���63Ha��� �)>� ?kaJ��lY )L�J�M�� \/?/�} ��7�R���q�4�:�p�p�:�89 � 03R;Cib �W .(�K�*[@�@[*[�)�����A�2��&�1 �FT ?()�2@x� � �����?�)>� ?kaJ)��lY )L�J�M�� �n�}\�)0�7�S�:e4]��7�S�t28+ � 0�S2C� )w` �>��2�I*[%=�2��&UTj �� X�J?�2��K6M���L�J�M�� ?N#�O� ��\�+K]K� .-?g ��:�0�p�46��73q�t�89 � 0�tv E� ?wd�@x���I%+X5�2��&�Lf �B �2�y�2�X3���)��L�J�M�� ?N#�O� )� s.} �)7�t;7Y46��7�q�t�89 � 0�q2C_` ?i)�I������@'����&Y� �>? ?k� ��\�3&)&'��L�J�M��� �N#�O� )�\�+K]K� .-?o �'�3��S�7�46��7�q�t289 � 0�72C�5 �>? )N#�)�)�3� �2��& UV )w` .kaJ)���]K�������LmJ�M��� )N#�O� �� s.}\��13q3R3: 4]��73q�t28+ � 13p2CW +VA� �2��&Y� ?<b��������L�J�M��� )N#��O. ?� s?g\��130�13q 4]��73q�q38+ � 1��CW ?��6�Hb��\�)>� )LmJ�M��� :WmkaX3��&' �� �2K]KI���P �)q21�t3te4]��737�p38+ � 1�:;C<= �<= )�\��*��y&'�)>? .kaJ)�lY �L�J�M��� ?o.Q ��:2S37�7�46��7�73:389

2 ;

Page 18: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

� 1302Y�` �i?�2�y�2��XV�2��&C"V �� �2��K�X3����L�J�M�� ?N#�O� �E�}\/?��:21�t;qC4�:�p�p�p�89 � 1�1�C�5 )w` �B\�I�+KI*[����X;O^�2�?&��5 �FT �F X��]%+*[��%yJ)X;H�����*����)�)r�� � @[*[��J)��& � 1�R;C�5 )FT )FGX2�]%*���%yJ)X;H�����*'����&C�j .k� �<b�y�2~)�;�)��L�J�M��� )� �+K�K� .� /�s?n\�)0��1 46��7�q�7�89 � 13S2C�5 )FT )FGX2�]%*���%yJ)X;H�����*,��� X�@[��%� �L�J�M�� ?Q.P'�)7�R�R�46��7�7���89 � 1�tv�(� ?(���)�3�)r�KI���)Lf �!�*[�@x� � �)�)� �NA�2X��)����&��5 )<a*[��&�������LmJ�M��� �N#��O. �E }\/.�'��p�t�: 4,:2p3p�p38+ � 13q2C� ��j �<|�;KI���#�2�?&C_` ?i������)����@���L�J�M��� )N#�O� )E }\/?��R3:�:20�4�:�p�p3p389 � 1372�(� ?(���)�3�)r�KI���)Lf �!�*[�@x� � �)�)�2�?&C�5 �<b*[��&�������L�J�M��� )N#�O� )E }\/?�)S�:2721Y4�:�p�p3p389 �uR2p2C�5 )FT )FGX2�]%*���%yJ)X;H�����*,���5 �wj �B �I�+K�*x�2�3X;O����j .k� �<b�I��~)�;�)���2�?&�� ��AX;H|�2@[*[�.���)�)r�� � @[*[��J)��& �uR��C� '�j �<b����@[*��\���m .N�X2K�J��� � �)�I���'�2�?& N �>� '<|�;KIJ����I�]K��.LfX�@[M�l5���]z L�@x���]K�*x%�AB ��%yJ��)X�@[X��3M�����& E��)�3*������I*[�)�Ys�- �

S�p�R�46��737�S�89 �uR�:;C� �k� �<b�I��~)�;�`����&Y�5 �FT )F X��]%+*[��%yJ)X;H�����*���L�J�M��� )� �+K�K� .� /�h\/?�)0�137Y46��7�q21�89 �uR202C� �k� �<b�I��~)�;�`����&Y�5 �FT )F X��]%+*[��%yJ)X;H�����*���� X3@���%2 �L�J�M��� .Q?P �)721?�V4]��737)��8+ �uR;1�C� �k� �<b�I��~)�;�`����&Y�5 �FT )F X��]%+*[��%yJ)X;H�����*���� X3@���%2 �L�J�M��� .Q�g\�'��R)��0C46��737�0�89 �uR�R;C�5 )w` �B\�I�+KI*[����X;O���L�J _j �K�J)���]*x��8{�?�6KI* KI��K�� X�c � X3@���%+�)@x�2�#LmJ�M���*[%��|LfX�@[*[��J��#%���&���ljMeX�cf(�%*�����%+��� 4�:�p�p3p389 �uR2S2C�5 )w` �B\�I�+KI*[����X;O^�2�?&��5 �FT �F X��]%+*[��%yJ)X;H�����*���B ��(��������2��K�����@[M�- ��0�0��V4,:2p�p���8+ �uR3tvC�5 )w` �B\�I�+KI*[����X;O^�2�?&��5 �FT �F X��]%+*[��%yJ)X;H�����*���>? �L�J�M��� (WakaX���&' )���;K]KI�� /�n �'��:2S��`4,:2p�p�:�8+ �uR2q2C�5 \FGX2�]%*���%yJ)X;H�����*a�2��& �5 wj B �I�+K�*x�2�3X;O��fkaX�l5r)�)KI�;KI*�X3���2@b� �+KIJ)X�&)� *[� (�%*�����%+���2��& B ��%yJ)��X�@[X���MZ} �|��p)�

4�:�p�p3p389 �uR272�(� ��5 �(�J)*[������*���� ��� ���,��� � ��� ��3. � ��JK���$�,��. �+�Z4�!�X���K�J W�X3@�@x�2��& �m!���H "�X��I���#��73q�p38+���]������@[��X��I�+c���������%+���

K�J���I�*[� � S�p2C�5 ?(�KI�I����& � �����?��N��O� �� X�&' )LmJ�M��� �}?h\�'��S��V4]��73q�q38+�)�]��� �2@x�]XV���c���I���%���bKIJ)��I�*[� � S)�C�� _j � �2��&)��� � E� � \� *�c �]��M�%2�\�j � �AX��]��O�*[%yJ � ����&Q89 'L \L�* Ky�2��O�����* �+� *�"+��. �,DN.�� F &:�)�, ?��@�� ?D 4�Lf�������2l5X��

L��I���I��?� X��?&�X�� ����7�q�S�89 � S3:;CN �ib ��A@�l5�3����� �)>� �E�@[�3�6KI*[%* K6M /�- �)1�:3t 46��73q3R389 � S�02C�5 )FT )FGX2�]%*���%yJ)X;H�����*,��� X�@[��%� �L�J�M�� �}\/?�'�v:;1�te4]��7�q�t28+ � S21�CN �� �2�3������()%+*[���%�`P�s�-'�'��p�03qC4]��7�q�t28+ � S3R; E� .� �i���*[*[���)N ?(' ��\�����������2��&�>? )Ld�2�I�.��>? �� �2K���I*x�2@ (�%+*[��?%+�`P?s ��1313p�S�46��7�q3q389 � S�S2CN �>? �<|�;KIJ)�I���6K�����&C�m �N#X�K�J)��� � �)���?��8{�3K� �>? �E��)�� .(�%+*, .P?} �)0�t;0�46��73q�q�89 � S�tvC� �FT �� *[r����+K]KA����&Y� $89 )<b��@ KI�����)>3X��)�I���2@'X�c\KIJ)� �#%+X3���6KI*[%��2@\(�X�%*��K6MeX2cf��l5��I*[%��^g�n ��:��;t;7�46��73q�q�89 � S�q2C�5 )E� �E�O;�2������>? �L�J�M��� �_ P.P �'��q�t2pC4]��73q�738+ � S�72C�5 )FT )FGX2�]%*���%yJ)X;H�����*,��L�J�M�� )�\�+K]K� �� }.h �'��7�q�7�46��7�q37389 � t;p2C�5 )FT )FGX2�]%*���%yJ)X;H�����*'����&C�j .k� �<b�y�2~)�;�)��L�J�M��� )N#�O� ��Tn�h �?t�:�:3: 4]��7�q3738+ � t���(� �WA*��IX2Ky�]�\�)� ��%��X3lVX3@���%+�)@[����P?s �)73p�0�46��7�7�p�89 � t2:;�(� �WA*��IX2Ky�]�\�)>� .kaJ��lY )L�J�M�� �o?n �)0�721�7C4]��737)��8+ � t;02C�5 )E� �E�O;�2�����)E���&)���vO�X3�)����!A�HT(���I*[���=/�- � �;t;p�46��737)�v89 � tv1�C�5 )E� �E�O;�2�����$89 )>? �W���Ky%yJ)*[���]X3� �)�2�?&Y(' .k� )N#X��3��y���!��;K������ s�-�s\�'��:21�4]��7�7���8+ � t2R;C�� ?N#X2KIJ)�� � �)�I���)�j �� ?<a����@[*[� �)�2��&�>? �<|�;K�J��)�y�]K���!A�2K��)�I� s.-�n\��1�t;pY46��7�7���89

2�;

Page 19: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

� t;S2�UV )FG�*\����& (� �ib �Em&�H|�2�y&)���?kaX�l5r)��Ky�;KI*�X3���2@'LfX�@[M�l5��A(�%*�����%+�jP �)1�1Y46��7�73:389 � t�tv�UV )FG�*,��>? .kaJ)�lY )LmJ�M��� �o?}\�)03:3:2S�46��7�73:389 � t;q2C�5 )E� �E�O;�2������� )�j �!��;�2�?����J ���2�?&489 �>? )W��)KI%yJ)*[����X�� ���#%+KI�5� �KI�2@[@, �� �;K� )n.h\��:;1�S�0�46��7�73:389 � t;72�UV )FT �� *�@�K�X3� ��>? �� ��%yJ\ �L�J�M��� �(�X3@�*x&)��n�h �'�3��p�R 4]��7�7�:�8+ � q�p2CN �� �2�3�������#&)Ov����%+��&Y� �;KI��I*[��@[��- �?:2730C4]��7�73038+ � q)�C_` ?W ?<aX��2@,�T ?(���* c����]K����2�?&C>? .k� �(�J)*[@[@[%X�%y���)LmJ�M��� )N#�O� )E n�g ��1�:3t;1�4]��7�73038+ � q3:;C�5 )FT )FGX2�]%*���%yJ)X;H�����*,��� X�@[��%�)@x�2�|L�J�M��]*x%�#N#��r?X3�]Ky�D/�h\�'��:�7Y46��7373R389 � q�02 E� '�` )� �2��K��3�)N ?(� �� �2�3����������&�>� �<= �Ld�2�I���?ka�@[@���@[���#L X3@�M�l5��y�=/�- �)021�7C4]��737�S38+ � q21�C�5 �FT )FGX2�]%*���%yJ)X;H��]��*��2��&Y�5 �wj ?B\�I�+KI*[����X;O���kaX3l5r)��KI�2K�*[X�����@ � �+KIJ)X�&)�|*[� ()%+*[���%�D����&�B\��%yJ)�)X�@[X��3M /?��:3R

46��7�73S389 � q3R;C� ��j �� X3�)�I�*[��X5�2��&�N ?(' ��\����������ka�@[@���@[���#L X3@�M�l5��y�=/�}\��0�137�46��737�t�89 � q�S2C_` �L��y�2@[@ �2��&�N �� �2�3����� 8{��K� �>� )� ��%yJ ?()%+*, ?s?o\�)0�p�R 4]��737�t28+ � q�tv5T ?_j .�\�2�y���� ���` �(�*[��l`�)��&'������&Y(� �<bX���H��]K��y�)��>� )���;K�����*x�2@\()%+*[���%� }\��737C4]��7�7�t28+ � q�q2 Lf f(' B|J)��X�%��2�I*[��� UV E� (�KI�vO���X3�)@x�2��*[���\����&ZLf _` \Ld�2������*[X2KIX�r.X��)@[X3���\���y%yJ)*[O��^X�c#�Ar)r)@[*���& � ��%yJ?�2�)*x%�j}�Q �

:3t;1 46��737�t�89 � q�72CN �Wj �<|�2�)�3J)l^�2� �)>? )� ?(�J���%y��@[�+K]KI���)�j �� �1'�2��J)*x&�X;O�������& (� �(�Ky�;c �]K��IX�lY��!A�2K��)�I� s?o�P �)0�S3:C46��7�73q389 � 7�p2C�5 #FT #FGX2�]%+*[��%yJ�X;H��]��*,�A*[�=<� >�/ -�;�, ?��@��/&BAC"�D)�,��@�EGF�HI$���,��JK��L �����*M"$��./�,���,���N� �M�GO�./JPIM� >���Q<L��JR�&:� ?��. �+�y�

��&)* KI��& � MC� �B X����)M��2l^�j����&!89 ?��r)r.��)J)��*�l 4�FGX��I@[& (�%*�����K�*:S?%2�?(�*��)���2r.X��I������737�q�89��r ��p�t� � 7)�Yk� �<= �WA����Lf �FT ��\*��\���2��&�� �k� ?U=��*��^� �)� �3%+�IX�l5X�@[��%�)@����#s /.�)0)��1�RC46��737�q�89 � 73:;�UV )FG�*\����& (� �ib �Em&�H|�2�y&)����L�J�M�� �N��O� �E�-�g\��S)�;t;0C46��737�q�89 � 7�02 wj �wj �!AX;O�*[��X;Oe����&��5 )FT )FGX2�]%+*[��%yJ�X;H��]��*,�3L�J�M���*[%��#X2c K�J)�j(�X3@�*x& (�KI�2K�� n /?�'��7�t;p�46��7�737389 � 721�CN 'W '<|�2����J)l^�2�\�'(' �` �_=�2��KI�3�� (� (�Ky�;c �]K��IX�lY�'� '� 71�����J�*[&�X;O���BD .<= '� *�KI%yJ)��@�@,� �2�?& _j 'Wj .EA _A� � *�� �

(�%*�����%+�`P?g?g\��:2p���q�4�:�p�p�p�89 � 73R;C�5 )E� �E�O;�2��������&�� ��A@[&����I��X��\�)�#&�O;�2��%��&�� �;KI��I*[��@[�D/)P'�)S��vt 4�:�p�p�p�89 � 7�S2C� �<bX;H#*x%y�����j .kb��%�%+*[��K�X?��UV �B|J)X3��@[�*�c ����X��\������&Y� �B �y�vO����I���+K���L�J�M�� ?N#�O� )� �K]K� ?g.Q �'�1�q)��p�0 4,:2p3p)��8+ � 7�tvC<= �<b�I����&���@ �2��&�N ?(� ?�\�2�3������>� )� �2K�����*x�2@\(�%*�����%+� s.} ��R�q�q�R 4,:2p�p���8+ � 7�q2C�5 )FT )FGX2�]%*���%yJ)X;H�����*'����& w` )wj ?!�X;O�*��3X;O���B ��(�� �������]KI��I@�M�- �?R�4�:�p�p���89 � 7�72C� ?� )w��3�]*[@�*[�O��?(' �wj �_�l5* KI��*[�O���"V $86�]J�* � �3�]J�*��)����&YBD �(�J)*[����?�2�I*���L�J�M��� �N#�O� )< }.- �)721?��p)�V4�:�p�p3:389 �[��p�p2C� )Ld�����I*����@[@�X5�2��&Y�j �N��2J�l5��� �)>? ?kaJ)�lY )L�J�M��� .Q�}\��:2S3S3: 46��73q3:389 �[��p)�C>? �N �N��vMe����&Y� �NA�2J)l^�2�\�)>� ?kaJ)��lY )L�J�M�� ?g.h\��1�1�:�0C4]��73q21�8+ �[��p3:;C>? �N �N��vMe����&Y� �NA�2J)l^�2�\�)>� ?kaJ)��lY )L�J�M�� ?g�P ��1�:;1�0C4]��73q3R�8+ �[��p�02C�5 FT \FGX2�]%+*[��%yJ�X;H��]��*m����& �5 w` B ���K�*x�2�3X;O.�dkaX�l5r)��Ky�;KI*�X3���2@aL�J�M���*x%�VkaX3l5lj�)�)*x%�2K�*[X����e/�P /���/�P.P �fR3:2q

46��7�737389 �[��p21�C_` ?N �(0��)*[�I�����j .k� )W�X3@ K����2��&CFT ?UV �WAX�X;O������L�J�M��]*x%�Y4 �Al^�6KI��y&)�2le8|n'P'�)03q�q�46��73S�q�89 �[��p3R;C� ?(�r)��*[����N �FT $8{l5r.�M3���2��&Y� ?�� )�D@[�*[� �)L�J�M�� )N��O� �< P?o ��1�0�S3qC4]��7�q�1�8+ �[��p�S2C>? �N �N��vM3�)� ?k� �� X�X�&�M3�)�2��&Y� ?N��2J)l^��� ��L�J�M�� �N��O� )< s�P'�?t20�0�46��7�q3R389 �[��p�tvC>? �N �N��vM3�)� ?k� �� X�X�&�M3�)�2��&Y� ?N��2J)l^��� ��L�J�M�� �N��O� )< s.s �)q373RC46��7�q�S�89

2�5

Page 20: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

�[��p�q2CBD ��b����*[������&C>? �N )NA�vM���L�J�M�� ?N#�O� )< s.g\�?t;721�pC4]��73q�q38+ �[��p�72U1 �1�J)X�� �)>? ?kaJ)��l� �L�J�M��� /./�n �)q�t2S�7C4�:2p3p)�v89 �[����p2C�5 )FT )FGX2�]%*���%yJ)X;H�����*,��� .k� )<b�y�2~)�;���)�2��&�� )Ld�2�I*[�)�@[@�X?��� X�@[��%� )L�J�M�� ?-?s �'�vR;1?�V4]��7�q�1�8+ �[�����C_` ?i)�I������@'����&Y� �>? ?k� ��\�3&)&'�)>? .kaJ)��l� �LmJ�M��� /�g �)0���q�q�46��7�q�1�89 �[����:;C_` �k� �FZ�2@[@[�3%+����*M"+��,JK. �/D ���/J ��@�R.�� O �,D)�, � & �e4 F *�@[�M3��!���H�"�X3�����'��7�t2:389 �[����02C>? �W )FG�*[�)�����M<� >�/ -�;�, ?��@��/&��N��@�"+� �+��@�R. �BF'&:�)�, ?��@�� ?D 4 F *�@[�M3��!���H�"�X3��������73q�0�89 �[���1�C� )Ld�����I*����@[@�X5�2��&Y�j �N��2J�l5��� ��L�J�M�� )N��O� �� �K]K� �n�- �'����7�S�46��7�q�p�89 �[����R;C� )Ld�����I*����@[@�X5�2��&Y�j �N��2J�l5��� �)>? )��r)r)@[*[��&�L�J�M��]*x%��-.P �?t���q�: 4]��73q)��8+ �[����S2�(� �!AX3��� �2��&Y� ��m )�D@���*��\��� X�@[��%� �L�J�M�� ?-?h �'��p3R3R 4]��7�q3038+ �[���vtvC�5 )FT )FGX2�]%*���%yJ)X;H�����*,���)�)r)� � @�*x��J)��&' �[����q2C�5 )FT )FGX2�]%*���%yJ)X;H�����*,��Lf )L�*[��y�2~�����*��)����&C>? �� ��� ��%y��*���>? ?kaJ)�lY )L�J�M��� .Q�}\�)S�t���p�46��7�q3:389 �[����72C�5 )FT )FGX2�]%*���%yJ)X;H�����*,��Lf )L�*[��y�2~�����*��)����&C>? �� ��� ��%y��*���>? �L�J�M��� �� /�} ��:)��7�te4]��7�q3038+ �[��:2p2C<= ��� ?W�X�@[*x�2� �?�` �E� �L ���I%�����)BD �BD )FZ�2�I�)X�%y�.������& Lf .� )F J)*�K�@[X�%y����L�J�M��� �N#��O� )E�-�h\�'��S3p�t 46��73721�89 �[��:��C�5 )w` �B\�I�+KI*[����X;O^�2�?&��5 �FT �F X��]%+*[��%yJ)X;H�����*���L�J�M�� )N��O� )E }?h\�?t;S�:2S�46��7�7�7�89 �[��:�:;C�5 )FT )FGX2�]%*���%yJ)X;H�����*,��kaX�l5r)��Ky�;KI*�X3���2@'� �K�J)X�&)�#*[� (�%+*[��?%+� �2��&YB ��%yJ)��X�@[X���MY-'�)q��54]��737�738+ �[��:202C>? �� �<|�����3����� � ? -��@��U*M"$��. �,���� .�� #"$� � �������� <L � �^4�Lf��I�3��l5X�� ���B9�c�X��y&'�'��73S�0�89 �[��:;1�Cib �W .(�K�*[@�@[*[�)�������)EA �� �_�*x� �2�I�*[X��)����&CN ��� )��X��I�)����vM���>� ?kaJ��lY )L�J�M�� ?n.h\�'��R�S21Y46��73S21�89 �[��:�R; FT ?UV �WAX�X;O������FT �BD ����]J��)�y�6K��)�2��&�N ?U=�IX;O�������>? ?kaJ)�lY )LmJ�M��� .-.Q'�'�v:�R27C46��7�t2:389 �[��:2S2 FT ?UV �WAX�X;O������! )EA �W�X�X;O�����������&Y�5 )W���?�]X3� �)>� �kaJ)�lY �L�J�M�� �Q�h\�'��q30�t 46��7�t;7�89 �[��:3tvC�5 )FT )FGX2�]%*���%yJ)X;H�����*'����&C�j .k� �<b�y�2~)�;�)��>? �L�J�M�� .kaJ��l5*[�]K��IMeX�cd(�X3@�*x&)�#n'-'�)7���0�46��7�q21�89 �[��:2q2C� )Lf .B �vM�@[X�����N ?W����Ky��%yJ)�3���)����&C>? �WA��I�+c��@x&'��L�J�M��� �N#�O� )�\�+K]K� .}�P'�)q3p�p�46��7�q�7�89 �[��:272C�5 )FT )FGX2�]%*���%yJ)X;H�����*,��L�J�M��]*x%�5� P�s�P �?t2:20Y4]��7�73S38+ �[��0�p2C�5 )FT )FGX2�]%*���%yJ)X;H�����*,��� .k� )<b�y�2~)�;���)�2��&�_j ?i)�I��)�3�@,��L�J�M���*x%�5� /�o.}\��R���7�46��7�730389

687

Page 21: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

B �A<|� E�8,W2Ld�2�y�2l5�K���y�fX2c?K�J)���6KI��&�*[��&5�6KI���?%9K��������d�;Km%+@[X3���|r���%y��*[�)���2�����i *[�� u:���K�J)��&�*x�]KI�2�?%+���d�����|�3*�O3��V*��5�)�)*�KI�mX2c� fB|J)�|lVX3@���%+�)@[�|pA*x�d�2@[Hb�vM�� r)@x��%+��&j�2K KIJ)�|X��I*��3*��`X2c)KIJ)�#%+X�X��y&�*[���;KI�a��M��]K���lY�2*� �� c�X��f����%yJ`�]K��I��%+K��)�I������������ � B|J)�AK6HaX�z &�*[l5�����*[X�����@)O�X3@��)l5�j4 *� �� fKIJ)���������38fr.��br����]KI*[%@���X�c'K�J)�=%+X3���]*x&�������&^�6KI����%+K��)�I���2Ka%+@[X3����r��3%y��*��)�j*[�a� 0�����@K�X���������������������� ��"! # ���������������$�%� ��"! &�' � ��H#J)����� ' � ��(jc�X��|KIJ)�*),+ -$.0/1+ .2-�34��57698:6�; �2�?& ' � ��<Vc�X��|KIJ)�*),+ -$.0/1+ .2-�3��>=V

Lf���Ky�2l5��y�bL� �@?A��"! �B(DC <E F<EG�HEI�J�IFKL(�NM �OJLC PJ,KPJ�J, LHLQEIRJ

# �@?A��"! �S<�C (�K�HL �HEIFTEILIF(EM � # �@?U��"! & (

V � �W V MX�SY & Q

W��r)KI�2l5���I�#�� �@ZN��"! �WKPC EQFH�HLH�GEQFKEIFH�NM �OJLC TPJ[<�<R(FHLKDJ,TLK

# �@ZN��"! �BQDC QDJ$QF E(�J$ �G�KE(EM � # ��ZN��"! & (

V � �W V MX�SY & I

W���r�KI��lV���I�#<� �@\]��"! �WKDC LQ�H�H�HLGLQ�KEI�H�NM �OJ�C K�HEQFH�TLT�TPJ$(�J

# �@\]��"! �BQ�C^QFKLGL(FTLT� PJ,HEIEM � # �@\]��"! & (

V � �W V MX�SY & I

W���r�KI��lV���I�Ak� �@_A��"! �SHPC LK� �TL �HLK�TDJ�(# �@_`��"! �WQDC Q�KEIRJ$K�TPJ$QLIFHV � �S PC (�GF<LKLT�HL F<RI�Q� M �SKPC PJ$Q�<RQFKPJ,TLQ�H M �S PC@J�(FK� EQFTL F<LHPJV M � a V �

��bc�OJLC (�G�KL(�KL(EIF(FHLT�bd�B(DC^IFH�GLQ�H�TEQLI�GLGV b �W PC@J$HF<�<E L(�T� �KL ��ec�S<�C (�T�G�HLGLQ�TL(�(LQ�ed�B(DC GLTDJ,HE(FGLHL(�Q� V ef� a V b

σ

ϕψ

i 8]UV � W�U=�X�l5�K��IMeX2c#4 ��8�KIJ)� r.���KI��lV�����2��&Z4 � 8aK�J)� J��r�Ky�2l5��4g l5X�@[��%+��@����[h[

6 2

Page 22: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

B �A<|� E 8 8,WjB|J�� � 03�?�;K�*[X�� X2c��6Ky�;K�� ����& KIJ)� �)�)*�K %+�@[@^r����I��lV�K����I� 4���9�KI�I��r?X3@[�2K���&TK�X KIJ)� K�J)����l5X�&�M����2l5*x%@[*�l5*�Ky8 X2c K�J�� �]K���&)*���& �]K��I��%9KI�)����� X�c K�J)� r?����KI�2l5���I� �2��& KIJ)� J)�r�Ky�2l5��y�� B|J)� r��2�y�2l5�K���y� ������&)�S��)��&����c�X3@�@[X;H��������� ���9����������� � ��� & � � �����9���������%� ��"! �:��� �����������������%� � � � & � �����������������%� ��"! � # � ��� ���9����������� � � #[&�# ������������������� ��"! � ���� ���� � a �P� & �P� �����9���������%� ��"! �U �� ���" � a F�� &F# � �����9���������%� ��"! � H#J)����� � *[�=KIJ)� 4 K6HbX2z{&�*�l5�����]*[X��?�2@ 8�O3X�@[�)l5��4 *� �� `K�J)�^�������38X2c\K�J)� ��M��]K���lY�R�26 # �2�I�AKIJ)�D�]*x&����bX�c K�J)�54��I��%+KI���)���)@x�2�98d���)* K�%�@[@���� � �����9���������%� ��"! 69� ��� ���9����������� ��"! 6 # ��� ���9����������� ��"! &����X2K���K�J��%+@[X3��� r��3%y��*��)� @�*[l5* Ky��X�c�� 6��26 # c�X���K�J�� ),+ -�.2/ + .�-�3 �c57698:6�; 6%=V� �2��& � � 69 � 6 V � ����� KIJ)�5�vO���y�2�3� %+X�X��y&�*[���;KI���A����&X��I*[���KI�2K�*[X����jX2c�KIJ)���,z,K�J lVX3@���%+�)@[� X�c�K�J������)* K^%+��@�@ 4��]����i *[�� u:�89 i�X��`K�J)�!S��y�6K`K�J)�I��Y�]K��I��%9KI�)����� KIJ)��Ov��@������VX2c��M 6 V � 6 V M5�����5�)X�Kj�]J�X;H#� � ��%��2�����VK�J)��M �2�I���\�����]r.��%+K�*[O��@[M��\� 0����2@�K�X ��� & (�69 P6 Y &�' 4�H#J)����� ' � Q c�X�� r.���KI��l5��y��2�?& ' �>I c�X3�#J)�r�Ky�2l5��y�y8mH#*�K�J�*��YKIJ)�D�9�r?����*[l5���KI��@'��I��X3�� |�� ��� ��� ����� �����

������� �"!#��$&%'�( �I*)>O ­�+ ,"-�,�. � 8 < ­�+ ,�­�­�. 8 ­ < ­�+ ,�, � ."- � 8 < ­�+ ,�,�­�­ �"/ 8 - <00� I*)2O ­�+ , � - � � 8 / < ­�+ ,�,�. � - 8 � < ­�+ ,�, � ,�­ / 8 < ­�+ ,�,�,�. / � 8 - <1 � I*)>O ­�+ ,�, � - 8 � < ­�+ ,�, � ��."- 8 � < ­�+ ,�,�,�. � � 8 - < ­�+ ,�,�, � / � 8 � <� � N ,2+ -�- � � 8 � < ,0+ - � �/ � , 8 � < ,0+ - � � ,"- � 8 - < ,0+ - � ­ /�/ 8 � <

34��5��6�"!#�7$&%'8( �I:9>O ­�+ , � - � - 8 � < ­�+ ,�, � ­ /�/ 8 / < ­�+ ,�, � � � � 8 / < ­�+ ,�,�, � ­ � 8 � <0 � I:9>O ­�+ ,�­�­�.�. 8 ­ < ­�+ ,�, � - / � 8 � < ­�+ ,�,�­�­ � � 8 � < ­�+ ,�,�, � - � 8 � <1 � I:9>O ­�+ ,�­ � ­ 8 � < ­�+ ,�, � - 8 � < ­�+ ,�,�­ � ­ � 8 - < ­�+ ,�,�, � � 8 � <� � N ,2+ � � / � 8 � < ,0+ � ­ � , 8 � < ,0+ � � � 8 - < ,0+ � � . / 8 � <

3'�750� �"!#�7$;%'<( �I*=2O ­�+ , � � / � 8 � < ­�+ ,�, � � ­ � 8 / < ­�+ ,�, � � � � 8 � < ­�+ ,�,�, � ­�, 8 - <0 � I*=-O ­�+ ,�­�.�. � 8 � < ­�+ ,�, � � . 8 � < ­�+ ,�,�­ / � � 8 - < ­�+ ,�,�, �"- � 8 � <1 � I*=2O ­�+ ,�, � / , 8 � < ­�+ ,�,�­ � , 8 - < ­�+ ,�,�, � � 8 � < ­�+ ,�,�,�­ , 8 � <� � N ,2+ - - � � 8 - < ,0+ - ��­ 8 < ,0+ -�- / � . 8 � < ,0+ -�- � � � � 8 � <

3'�750� �"!#�7$;%?>( �I*@>O ­�+ , � - � , 8 � < ­�+ ,�, � � - 8 � < ­�+ ,�, � -�, � 8 � < ­�+ ,�,�, � ­�. � 8 . <00� I*@2O ­�+ ,�­7-�­�, 8 - < ­�+ ,�,"-�­ � 8 � < ­�+ ,�,�­ � � ­ 8 � < ­�+ ,�,�,"-�­�,"- 8 <1 � I*@>O ­�+ ,�­�,"- � 8 � < ­�+ ,�, � , � 8 � < ­�+ ,�,�­�,�­ / 8 � < ­�+ ,�,�, � ,"-�. 8 - <ACB ,2+ � / - � � 8 - < ,0+ � / - � . 8 � < ,0+ � / - � . � 8 � < ,0+ � / - � . � 8 ­ <� N ,2+ ��, � ,"- 8 � < ,0+ ��, � , 8 ­ < ,0+ ��,�, �/ - 8 ­ < ,0+ ��,�, � ,"-�. 8 - <� N ,2+ , � � �/ 8 � < ,0+ , � � ��, 8 . < ,0+ , � � � 8 ­ < ,0+ , � � � 8 � <A N ,0+ � / - � � 8 � < ,0+ � / - � . 8 � < ,0+ � / - � . � 8 � < ,0+ � / - � . � 8 ­ <� Q ,2+ � ­ ."- 8 � < ,0+ � ­ � .�. � 8 / < ,0+ � ­ � ­ / ­ 8 ­ < ,0+ � ­ � / . � � 8 � <� Q ,2+ ��, � � � 8 � < ,0+ ��,�­ � � - 8 / < ,0+ ��,�, ��,�. 8 ­ < ,0+ ��,�,�­ � � - 8 � <A Q ,2+ ­ -�- � 8 - < ,0+ ­ -�-�­ 8 � < ,0+ ­ -�-�, � 8 � < ,0+ ­ -�-�, � 8 � <�ED ,2+ � � � .�. 8 � < ,0+ � ­ , 8 � < ,0+ � ­ � / � 8 � < ,0+ � ­ � ­�, � 8 � <��D ,2+ � � / .�­ 8 � < ,0+ � � -�­�. 8 � < ,0+ � � � / � � 8 � < ,0+ � � � -�­�.�­ 8 - <A D ,0+ ­ -�- � 8 � < ,0+ ­ -�-�­ 8 � < ,0+ ­ -�-�, � 8 � < ,0+ ­ -�-�, � 8 � <

686

Page 23: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

B �A<|� E 8 8 8,W B|J��V&�*[l5�����*[X��)@[���I�A��@[�3�6KI*[%`%+X3lVr�@�*x�2��%����X2c�KIJ)�Vr?���3Ky�2l5��D��M��]K���l *���K�J)�V�I��%9Ky�2�)�3�)@x�2����X�@[*x& r)J��3�]�3 B|J)� &�*[l5�����*[X��)@[���I�br)���������)�I�D*[�#&���S��)��&��3��W���� ��� � b

&����

� � � � ��� � �� ����� ������� � ������R2S ��R 130�t�46�3��8��RJ, �� :2q3p�4�R38���J, �� z{:�0)�34 t28��RJ, �� �vR�:)4 1�8��RJ, ��:3:;1 ��R 130�:)4�738���J, �� :3t2q�4,t�8���J, �� z{:�0)�34,R�8��RJ, �� �vR27�4,R�8��RJ, ��q37�S ��R 1�:�7�46�3��8��RJ, � :3t2p�4,t�8���J, � z{:3:�R)4�q38��RJ, � �vR2q�4,R�8��RJ, �� ��R 1�:�7�46��p38��RJ, �� :3t�:)4,t�8���J, �� z{:3:3t�4 t28��RJ, �� ��S�p�4,R�8��RJ, ��R2S R2p 021?�346�v:�8��RJ, �� ��q3S�4 0�8���J, �� zI��1�R)4�S38��RJ, �� 73:21?4]�vt28��RJ$ ��:3:;1 R2p 0�037�46�3��8��RJ, �� ��q30�4�1�8���J, �� zI��13p�4�S38��RJ, �� 73:�q�4]��R�8��RJ$ ��q37�S R2p 021�R)4,R�8���J, �� �vt2S�4�:38���J, �� zI��021?4,:�8��RJ, �� 73:�p�4]��:�8��RJ$ ��� R2p 021�0�4 t28���J, �� �vt2q�4 0�8���J, �� zI��03R)4�038��RJ, �� 73:�0�4]��038��RJ$ ��R2S ��R2p 0�030�4,R�8���J, �� ��q�R)4�:38���J, �� zI�v:3t�4,:�8��RJ, �� 7�1��34�738��RJ, ��:3:;1 ��R2p 0�0��34,R�8���J, �� �vt27�4 0�8���J, �� zI�v:2p�4,:�8��RJ, �� 73R�S�4]��p38��RJ$ ��q37�S ��R2p 03:�t�4�S38���J, �� �vt27�4 0�8���J, �� zI�3��q�4�038��RJ, �� 73:�7�4]��S38��RJ$ ��� ��R2p 03:�q�4�S38���J, �� �vt2q�4 0�8���J, �� zI�3��q�4�038��RJ, �� 721�p�4]�1�8��RJ$ ��R2S R2p�p :273p�4�S38���J, �� ��S�:)4�:38���J, �� zI��p�7�4�038��RJ, �� q3:�q�4]��:�8��RJ$ ��:3:;1 R2p�p :3t2q�4�038���J, �� ��S3p�4�:38���J, �� zI��p3R)4,:�8��RJ, �� q)��7�4]����8��RJ$ ��q37�S R2p�p :2q30�4,R�8���J, �� ��S�:)4�:38���J, �� zI��p21?4�038��RJ, �� q)��q�4]��S38��RJ$ ��� R2p�p :3t27�4 1�8���J, �� ��S��34�:38���J, �� zI��p21?4�038��RJ, �� q)�;t�4]�1�8��RJ$ ��

689

Page 24: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

B �A<|� E 8{w W�B|J���&�*[l5�����*�X3�)@[���I���@x���]K�*x%�%X�l5r)@[*[����%+����X2c�KIJ)�AJ)��r�KI��l5��a��M��6KI�l *[�^K�J)�=� r)J?������ fB|J)����M�l � X�@x�m�2�I�K�J�� ����lV� �3�|*�� B � � @[� 8 8 89

� ��� � ��� � ������ � ������� � �� �R2S �vR S37�7�4]��R38��RJ$ �� t;13S�4]��0�8��RJ$ �� �137?4 7�8��RJ$ �� :2p��34 t28���J, ��:�:;1 �vR S3q3:)4]��p�8��RJ$ �� t�:��34]���v8��RJ$ �� ��S�p?4,t�8��RJ$ �� ��q3p�4,:�8���J, ��q�7�S �vR S3q3:)4]���v8��RJ$ �� t2p�S?4 738��RJ$ �� ��S)�34]��0�8��RJ$ �� ��q3p�4,:�8���J, ��� �vR S�t;7�4]��p�8��RJ$ �� t2p�t)4 738��RJ$ �� ��S�0�4]��p�8��RJ$ �� �vt2q�4]��8���J, ��R2S R�p R�t���4�R�8��RJ$ �� S���R�4 S38��RJ$ �� ��:;1.4,t�8��RJ$ �� ����1?4,:�8���J, ��:�:;1 R�p R�t;p?4 S38��RJ$ �� S�:2p�4]��:38��RJ$ �� ��0�7?4�R38��RJ$ �� ���vR)4,:�8���J, ��q�7�S R�p R�S�t)4,t28��RJ$ �� S3p)�34]���v8��RJ$ �� ��:�R�4 S�8��RJ$ �� ��p37�4,:�8���J, ��� R�p R�S�q?4,t28��RJ$ �� S3p�q�4]��:38��RJ$ �� ��:2q?4 S�8��RJ$ �� ����p�4,:�8���J, ��R2S ��R�p S303R�4,t28��RJ$ �� S37�S?4,t28��RJ$ �� �130?4,t�8��RJ$ �� �3�vt2p�46��1�8��RJ, ��:�:;1 ��R�p S�:;1.4,t28��RJ$ � S37�p�4]��:38��RJ$ � �13S?4,t�8��RJ$ � �3��03S�46�v:�8��RJ, �q�7�S ��R�p S��vt)4,t28��RJ$ �� S3S21?4]���v8��RJ$ �� ��0)��4 7�8��RJ$ �� �3�1�7�46��038��RJ, ��� ��R�p S���q?4,t28��RJ$ �� S�t��34]��:38��RJ$ �� ��0�t)4 q�8��RJ$ �� �3��037�46�v:�8��RJ, ��R2S R2p3p R�S�q?4�R�8��RJ$ �� S���7?4�R�8��RJ$ �� ����7?4�R38��RJ$ �� ��p)��S�46��p38��RJ, ��:�:;1 R2p3p R3R;1.4 S38��RJ$ � R�7�7?4 738��RJ$ � ��:2q?4�1�8��RJ$ � ��p�p37�46��p38��RJ, �q�7�S R2p3p R�S�t)4,t28��RJ$ �� R�q�q?4 S38��RJ$ �� ��:�:�4 S�8��RJ$ �� 7�7�q?46�v:�8���J, ��� R2p3p R�S�p�4]��p�8��RJ$ �� R�7�p�4]��p�8��RJ$ �� ��:2S?4�R38��RJ$ �� ��p�p3p�46�v:�8��RJ, ��

6 6

Page 25: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

B �A<|� E w W�B|J��=&�*[l5�����*[X��)@[���I�|�@x���]K�*x%�%X�l5r)@[*[����%+���bX2c KIJ)� J)�r)KI�2l5���|��M��6KI�l *[�CK�J)� < r)J?������ dB|J)�D�]M�l � X�@x�#�2�I�K�J�� ����lV� �3�|*�� B � � @[� 8 8 89

� � � ���� � ���� ��� ������� � ������R2S ��R :�:20?4 0�8��RJ$ �� q373:�46��7�8���J, �� z{S�0��34]��q38��RJ$ �� �3��q?4�:�8��RJ$ ��:3:;1 ��R :���7?4�1�8��RJ$ �� q�S��34,t�8���J, �� z{S�p3S�4]��:�8��RJ$ �� �3�1.4�:�8��RJ$ ��q37�S ��R :��vt)4,t�8��RJ$ �� q�13q?46���v8���J, �� z{S3:3:)4,:�:�8��RJ$ �� �3��0?4�:�8��RJ$ ��� ��R :��vt)4 S�8��RJ$ �� q21�t�4 q�8���J, �� z{S)�v:)4]��q38��RJ$ �� �3��0?4�:�8��RJ$ ��R2S R2p ��:27?4�:38��RJ$ �� S�p�t�4 q�8���J, �� z{:)��S?4 q38��RJ$ �� t3t�t)4�R�8��RJ$ ��:3:;1 R2p ��:2S?4�:38��RJ$ �� R2q�1?4�R38���J, �� z{:�p�p?4 738��RJ$ �� t;S3q�4]��038��RJ$ ��q37�S R2p ��:�R�4�:38��RJ$ �� R3t3t�4�R38���J, �� zy��73S�4]��p38��RJ$ �� t;0��34]��:�8��RJ$ ��� R2p ��:�R�4�:38��RJ$ �� R3t2S�4�R38���J, �� zy��7�R)4]����8��RJ$ �� t;1�t)4 S38��RJ$ ��R2S �vR2p ��0�0?4�:38��RJ$ �� S3R�p�4 S�8���J, �� zy��7�R)4]��p38��RJ$ �� q�:2S?4 738��RJ$ ��:3:;1 �vR2p ��0�0?46�v8��RJ$ � S�03S�4�1�8���J, � zy��q30�4]��p38��RJ$ � t27�7?4,t28��RJ$ �q37�S �vR2p ��03:�4�:38��RJ$ �� S21?�34 7�8���J, �� zy��q3q�4]��:�8��RJ$ �� q�p�t�4]����8��RJ$ ��� �vR2p ��03:�4�:38��RJ$ �� S�0�t�4,t�8���J, �� zy��q�1?4]����8��RJ$ �� q3p�p?4 738��RJ$ ��R2S R�p�p ���vt)4�:38��RJ$ �� R2q3p�4 S�8���J, �� zI�vR2q?4 q38��RJ$ �� t��1.4,t28��RJ$ ��:3:;1 R�p�p ���vt)4�:38��RJ$ � R3t�:)4 S�8���J, � zI�vR3t)4 S38��RJ$ � S3q�t)4 738��RJ$ �q37�S R�p�p ����S?4�:38��RJ$ �� R2q��34 7�8���J, �� zI�vR�R�4 738��RJ$ �� S3q3R�4 738��RJ$ ��� R�p�p ����S?4�:38��RJ$ �� R3t2S�4 q�8���J, �� zI�vR2S?4 q38��RJ$ �� S3q)��4 738��RJ$ ��

6��

Page 26: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

B �A<|� E w 8,W�B|J���&�*[l5�����*�X3�)@[���I���@x���]K�*x%A%X�l5r)@[*[����%+���dX2c'KIJ)�AJ��r�Ky�2l5��|�]M��]K���l *[�^K�J��Dk r)J��3�]�3 dB|J)����M�l � X�@x�m�2�I�K�J�� ����lV� �3�|*�� B � � @[� 8 8 89

� � � � ��� � ���� ��� � ����� � �� �03S ��R 73q)��46��q�8���J, �� S3S)��46���v8���J, �� 1�1?4]��p�8��RJ$ �� t3tv1.46��p�8���J, ���131 ��R 73S21.4�:�R38���J, �� S3S�0?46��R38���J, �� S�0�4]��p�8��RJ$ �� t;1�1.46��0�8���J, ��:�:21 ��R 73:�p�4 q�8���J, �� S21�7�4�1�8���J, �� R�:�4 q38��RJ$ �� t;0�S?4 q�8��RJ$ ��R3t2S ��R 7�:2q?46��R38���J, �� S21�R)4 S�8���J, �� 137?4 738��RJ$ �� tv1�1.4,t�8��RJ$ ��q�73S ��R 7�:2q?46��S�8���J, �� S�R2q?46��:38���J, �� 1�t)4 738��RJ$ �� t�:27?46�1�8���J, ��� ��R 7�:3t)46��R38���J, �� S�R�:�46���v8���J, �� R20?4 q38��RJ$ �� t20�0?46���v8���J, ��03S R2p t;q�R)4 S�8���J, �� R27�1?4�1�8���J, �� R���4�1�8��RJ$ �� S�p�p?4�1�8��RJ$ ���131 R2p t2q�t)46��R38���J, �� R3t2S�4,t�8���J, �� S�7?4 S38��RJ$ �� R3tv1.4 7�8��RJ$ ��:�:21 R2p t;S3S�4,t�8���J, �� R2S�R)4 S�8���J, �� S�t)4,t28��RJ$ �� R2S�t)4�R38��RJ$ ��R3t2S R2p t;1���46��:38���J, �� R2S�:)4,t�8���J, �� R3t)4 S38��RJ$ �� R2q)��4�R38��RJ$ ��q�73S R2p t�R���46��0�8���J, �� R3t�R)4 S�8���J, �� R2q?4 q38��RJ$ �� R�7�p?46��:38���J, ��� R2p t�R�R�46��0�8���J, �� R2S3S�4,t�8���J, �� S�0?4 q38��RJ$ �� R3t;S?4 7�8��RJ$ ��03S �vR2p q�0�1?4 S�8���J, �� S21�0�4,t�8���J, �� R2S?4�R�8��RJ$ �� S�0)��4 S�8��RJ$ ���131 �vR2p q���0?4�:2S�8���J, �� S�:3t)46�1�8���J, �� t;p?4 q38��RJ$ �� S��vt)46��:38���J, ��:�:21 �vR2p q30�p?46��p�8���J, �� S�R2p?46��p�8���J, �� t;q?4�R�8��RJ$ �� S)��S?4,t�8��RJ$ ��R3t2S �vR2p q���7?46���v8���J, �� S3:3R)4 q�8���J, �� tv1.4�R�8��RJ$ �� S3:;1.4,t�8��RJ$ ��q�73S �vR2p q30�p?46��p�8���J, � S�:2p?46��p�8���J, � R���4,t28��RJ$ � S3p�7?46��p�8���J, �� �vR2p q�:�:�46��R38���J, �� S�:2q?46���v8���J, �� S�p?4,t28��RJ$ �� S��1.46��p�8���J, ��03S R�p�p t3t;p?46��:38���J, �� R�t;7?46��0�8���J, �� S3R�4�R�8��RJ$ �� R�R2q?4 S�8��RJ$ ���131 R�p�p t20�S?46��p�8���J, �� R3R27?46��p�8���J, �� S�q?4 q38��RJ$ �� R;130?4�R38��RJ$ ��:�:21 R�p�p t�R;1.46��:38���J, �� R�R�q�4 q�8���J, �� S3:�4�1�8��RJ$ �� R�R�:�4 S�8��RJ$ ��R3t2S R�p�p tv1�7�4 S�8���J, �� R3t20�4�R38���J, �� S�t)4�1�8��RJ$ �� R2S)��4�R38��RJ$ ��q�73S R�p�p t2R)�34 7�8���J, � R2S�R)4 7�8���J, � S�p?4 738��RJ$ � R2S3:�4,t�8��RJ$ �� R�p�p tv1�R)4 7�8���J, �� R2S�:)4 q�8���J, �� S21.4,t28��RJ$ �� R2S�S?4,t�8��RJ$ ��

6 4

Page 27: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

B �A<|� E w 8 8,W'kaX�l5r��2�I*x�]X3��X�cd�����]�)@�KI��X � Ky�2*[�)��&�c�X3� � � Q�H5r?���3Ky�2l5��y���2K�K�J)�V&�*[lV������*�X3�)@�������r)���������)�I� � ��� QF +W4 ��8d� ��*�����@[��@�X3�)� �I�)� ��4 � 8���SDr����I��@�@[�@?���)�?�d*���* KI*[��@�*[���&5c���X3l O;����*[X����m�6KI����%+K��)�I�����������y�;K���&V*��5KIJ)�A@[X��)� �I�)� �x4 %�8fc�X3���Sjr��2�y�2@[@[�@��I�)���b*[�)*�K�*x�2@[*�����&^c��IX�l �`r?����*[X�&�*x%�@x�;K]KI*[%��X � KI��*�����& � M5�)�)*�c�X��Il �I%�2@[*[�)�jX�c'K�J)�D%+@[X3���Ar��3%y����&e�6KI���?%9K������3 _��+KI��*�@x�#X�c\K�J�� ���)�?�#�2�I�D&)*[�I%+���I����&C*���K���9�K�

�I�)� ���� ���������� � ����� � �� �4 ��8 030�S�R)46�vR�8��RJ, �� ��q303R)4�q38��RJ, �� zI��0�q�R)4,t�8���J, �� 73S�p?4,t28��RJ$ ��4 � 8 030�S30�46��S38��RJ, �� ��q�:20�4 t28��RJ, �� zI��0�q�R)4 7�8���J, �� 7�1�t)4 S38��RJ$ ��4 %�8 0303:�q�4�:3:�8��RJ, �� ��q303R)4�S38��RJ, �� zI��0�t2p�4 q�8���J, �� 7�R20?4 S38��RJ$ ��

B �A<|� E w 8 8�8,W�B|J�� �9�K��y�2r.X�@x�;KI��&YO;�2@[�)����X2cdKIJ)� �I���I%��@���& 4 � M KIJ)� c��I��`O�X3@��)l5� � �)@���l5X�&��)@[���I8��@x���]K�*x%j%X����]KI���3Ky��2�?&�&�*[����%9KI*�X3���2@ L X3*[�I��X�� �y�;KI*�X���*[� K�J��V%@�X��]�`r���%y��*[�)� @[*�l5*�K�c�X3�AKIJ)�Vr?���3Ky�2l5��y�=�2��&�J)�r�Ky�2l5��y�� =B|J)�V��I�IX��y�A�2�I�� �+K6Hb��� K6HaX`�2��&ec�X��)�br?���I%���K� 5 &)��)X�K����mK�J���r.���KI��l5��y���H#J)���������m�j��<�������&Ck &����)X2KI�AKIJ)�D�6KI��&�*[��&er�J��������aX2cK�J���J)�r)KI�2l5���I�� 8 Ka*[�mHaX3�]KIJ`KIX �)X�K�*x%+�|K�J?�;K = ���� *x���)���3�;KI*�O3�|c�X��dKIJ)�A�]K��I��%9KI�)�I����� ����& k� 3B|J�*[�m*�l5r)@[*������)���3�2K�*[O��O;�2@[�)���|X�c KIJ)� &�*[����%9KI*�X3���2@�LfX�*x����X����y�;K�*[X3�|��J)X;H#��*���K�J�� @[�3�6K|K6HbXV�IX;H���

5 8 ; == �� & ; ���� �3 p3S3R :� S�7�t �� u:2q�1 �� 7�q�0= ��� ��� & ; ���� �3 7�R20 :� uR���p :� uR273S :� uR2721= ���� & ; ���� p� S373R z{p) uR2S�R p) 03:�p z{p) u:2p3q= � � & ; ���� p� ut20)� p) 0�S3p p) uR��;t p) S213q

� �� p� 0�R�: z{p) u:�:3: p) [��:�0 z{p) p�q�1

� �� p� S3S�p z{p) u:2p�t p) u:2037 z{p) [��p37

6:;

Page 28: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

0

1

a

b

a

b 1

0

a

b

0

1

a

b

0 1

2 3

i 8]UV a:W B|J�� %+@[X3����r?��%y����& �]K��I��%+K��)�I���5*[� K�J)� 4��38Vr.���KI��lV��� �2�?& 4 � 8 z94 &?8VJ)�r�Ky�2l5��C�]M��]K��l^�� B|J)� �)�)*�KC%�@[@c�X��5����%yJ X�c�K�J)���]�Y�]K��I��%9KI�)�����V*[�V�I��%9Ky�2�)�3�)@x�2�� Q8{� K�J)�Y%�3�]�CX2c�K�J)��J)�r)KI�2l5���I�`K�J��M �2�I�ec����]KIJ)��5�I�+c���I�I��&ZKIXG�3�4 � 8DK�J��C<az �]K��I��%+K��)�I���#4 %�8DKIJ)�C��z �]K��I��%9KI�)�I��4�H#J)*x%yJ *x�`&��������� KIJ��2� K�J)��<mz{�]K��I��%9KI�)���e�2KV%@�X��]�^r��3%y��*��)��89�#4 &?8DK�J��kmz{�6KI����%+K��)�I�`4 H#J)*x%yJC*x�aK�J)�=l5X3�]K|&��������D�]K��I��%+K��)�I�AX�c K�J)�D���)X;H#�CJ)�r�Ky�2l5��|�]K��I��%9KI�)�����|�;K#%+@[X3���Ar��3%y��*[�)�C� R3R���R2qv�89 B|J)�Dl5X�@[��%�)@[���#X��I*�����KI�;KI*�X3����� V �������D*[��&�*x%�;KI��&C*���KIJ)*[�'S?���)�I� � M @�*[�)� *[�3KI��IO;�2@x�aX�c X3��*[���KI�2K�*[X���� Q V c�X��#r.���KI��l5��y��2�?& I V c�X��#J��r�Ky�2l5��y�

6 ;

Page 29: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

1 1.02 1.04 1.06

V/V (C)c p

10

100

1000

p * B

A

C

i 8]UV 0+W^B|J)�e*[�X2KIJ)��Il^� X�cA&������� ��X�@[*[& �]K��I��%+K��)�I��� c�X�� KIJ)� J��r�Ky�2l5��V�]M��]K��lY ��� � � & � �@_A��"! H#J)����� � *x� K�J��K6HbX2z{&�*�l5�����]*[X��?�2@AO3X�@[�)l5� 4�*, �� K�J)�Z�2�I����85X2c KIJ)�Z�]M��]K��lY�=�2��& ���@_A��"! &)��)X�K����C*�KI�COv��@�����c�X3� KIJ)� �]K��I��%9KI�)�I� =�;K^%+@[X3��� r?��%y��*����P� ���^*x�`K�J)�Y&�*[l5�����*�X3�)@[���I�`r����������)�I� &��S?�)��& *�� B � � @��!8 8�89 8 K^%��2� � �Y�]���� KIJ��;KVK�J��C*x�]X�K�J)����l%+X3���I����r.X���&�*[�)�DKIX K�J)�=<az �]K��I��%9KI�)�I�#*[�a@�X�%��;K���&^� � X;O��|KIJ)�A*[�X�K�J)����l X2c'KIJ)����z �]K��I��%9KI�)�I����H#J�*[%yJ ��*[�^K��)�I� ��*[�a@[X�%��;KI��&� � X;O���K�J�� *[��X2KIJ)��Il X2c K�J��`kmz �]K��I��%9KI�)�I�`�uR�R��.R2qv

6 5

Page 30: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

0 10 20 30 40

1 0 -6 N M C

30

32

34

36

105 S

* xxxx

D R AN D 48SN W S

0 10 20 30 40

1 0 -6 N M C

17

17.5

18

18.5

19

105

S* yyyy

D R AN D 48SN W S

0 10 20 30 40

1 0 -6 N M C

-15

-14.5

-14

-13.5

-13

-12.5

105

S* xxyy

D R AN D 48SN W S

0 10 20 30 40

1 0 -6 N M C

9

9.5

10

10.5

105

S* xyxy

D R AN D 48SN W S

0 10 20 30 40

1 0 -6 N M C

0.40

0.41

0.42

0.43

0.44

ν xy

D R AN D 48SN W S

0 10 20 30 40

1 0 -6 N M C

0.7

0.72

0.74

0.76

0.78

0.8

ν yx

D R AN D 48SN W S

i 8]UV �1+W#��� �9)�2l5r)@[�jX�cdK�J)�5��%�%+�)l`�)@[�2K�*[X�� r)@[X2Ky�AX�cA4 ��8 z94 &�8�K�J)�V&�*[lV������*�X3�)@��������@x���]K�*x%j%X�l5r)@[*[����%+���A����& 4��v8 z94 cI8K�J��jLfX�*x����X�� �y�;KI*�X���X � KI��*��)��&�c�X�� � �cQFH^r.���KI��l5��y��*[� K�J��j�I��%9Ky�2�)�3�)@x�2��r)J?�����j�;K � � �cQ� e��*�l`�)@[�2K���& � MY����*[�)�K6HbX5&)*�����I���K#�I����&�X3l ���)l � ��#�3��)���I�2K�X��y�������������54 c���@�@ �]M�l � X�@x�y8a����&N<��� 5< 4�X3r?���Y��M�l � X�@x�I8+

987

Page 31: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

0 10 20 30 40

1 0 -6 N M C

-20

0

20

40

105

S* ijkl

S *xx xx

S * yyyy

S *xx yy

S *xyx y

0 10 20 30 40

1 0 -6 N M C

0

0.2

0.4

0.6

0.8

1

ν ij

νxyνyx

i 8]UV mRW B|J)� ��%�%+�)l`�)@x�;K�*[X�� r)@�X�KI�5X�cV4 ��8jK�J)� &�*[l5�����*[X��)@[���I�V�@x���]K�*x%C%X�l5r)@[*[����%+���V����& 4 � 8`KIJ)�YL X3*[�I��X�� �y�;KI*�X��X � KI�2*[�)��&ec�X3� � �XG�TLHjr.���Ky�2l5��y�|*���KIJ)� ����%9Ky�2�)�3�)@[���ar�J������ �;K � � ��QF �

9 2

Page 32: 0/1 1streaming.ictp.it/preprints/P/03/007.pdf · 2003. 8. 2. · ®b + + + $+ +; + ¶¥ " ' + :; $ ' = $+; ; " + :; ' & * & + ; $ * %

1 1.01 1.02 1.03 1.04

V /V C P(stru c tu re )

0.95

1

1.05

1.1

p/p(F

V)

P entam erH eptam er AH eptam er BH eptam er C

1 1.01 1.02 1.03 1.04

V /V C P(stru c tu re )

0.8

0 .9

1

1 .1

1 .2

BT

/BT

(FV

)

P entam erH eptam er AH eptam er BH eptam er C

1 1.01 1.02 1.03 1.04

V /V C P(stru c tu re )

1

1.5

2

2.5

3

Cxx

xx /B

T(F

V)

P entam erH eptam er AH eptam er BH eptam er C

1 1.01 1.02 1.03 1.04

V /V C P(stru c tu re )

1

1.5

2

2.5

3

Cyy

yy /B

T(F

V)

P entam erH eptam er AH eptam er BH eptam er C

1 1.01 1.02 1.03 1.04

V /V C P(stru c tu re )

-1

-0 .5

0

0 .5

1

Cxx

yy /B

T(F

V)

P entam erH eptam er AH eptam er BH eptam er C

1 1.01 1.02 1.03 1.04

V /V C P(stru c tu re )

0

0.2

0 .4

0 .6

0 .8

1

Cxy

xy /B

T(F

V)

P entam erH eptam er AH eptam er BH eptam er C

1 1.01 1.02 1.03 1.04

V /V C P(stru c tu re )

-1

-0 .5

0

0 .5

1

νx y

P entam erH eptam er AH eptam er BH eptam er C

1 1.01 1.02 1.03 1.04

V /V C P(stru c tu re )

-1

-0 .5

0

0 .5

1

νy x

P entam erH eptam er AH eptam er BH eptam er C

i 8]UV \S$W B|J��^�9�r?����*[l5���KI��@�&)�;Ky��X � Ky�2*[�)��& c�X��DKIJ)�^r.���KI��lV���I�^4 X�r.�� %+*[�y%+@[���y8�����& K�J)�^J��r�Ky�2l5��y�^4 KIJ)�^r)J��3�]���� �.<�����& k������D�I�r)�I�������KI��& � M�&�*x�2l5X���&������0����2�I�����)�2�?& %+�IX3�I�]������I����r?��%9K�*[O���@�M)8|&�*[O�*[&)��& � MMWdK�J)��*�������M�l5r�KIX2KI*[%��X � KI�2*[�)��&e*[� c��y�2l5���bX�c K�J)�=c��I��=O�X3@��)l5�D�2r)r���X)9�*[l5�2K�*[X��^c�X3� 4 �38�K�J��=r����������)�I���2�?& 4 � 8mK�J)� � �)@[�el5X�&��)@[����������& � MK�J�� c������ O�X3@��)l5� ���6KI*�l^�;KI� X2c K�J)� � �)@[� l5X�&��)@[���#c�X3�j4 %�8 z94 cI8#K�J)� ��@[�3�6KI*[%D%X����]KI���3Ky� bB|J)� �@x���]K�*x% %+X3���]KI�2��Ky���= ������� �Hb��I�=%��2@x%+�)@x�;KI��& � MeK�J)�Dc�X3��l`�)@[���V4 t28b�2�?& 4 1�89 �8{� 4 ��8b�2��&G4�J.8bHa� ��J)X;H K�J�� L X3*[�I��X�� �y�;KI*�X��bX � Ky�2*[�)��& c���X3l 46��p38+

986