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View Full Version : Different signs in connections of QED and YM


Rene Meyer
Aug7-04, 05:05 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Hello,\n\nI was wondering if there is any physical reason or reason of\nconvenience to use different signs in the comparators for QED gauge\ntheory and YM theory, as Peskin/Schroeder do:\n\nU(1): U(x+eps n, x) = 1 - i e eps n^mu A_mu(x)\n\nSU(2): U(x+eps n, x) = 1 + i e eps n^mu A_mu^i(x) sigma^i/2\n\nWouldnt it be more convenient to use the same sign in both cases?\n\nRene.\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">&nbsp;&nbsp;View this Usenet post in original ASCII form </a></div><P></jabberwocky>Hello,

I was wondering if there is any physical reason or reason of
convenience to use different signs in the comparators for QED gauge
theory and YM theory, as Peskin/Schroeder do:

U(1): U(x+eps n, x) = 1 - i e eps n^\mu A_{mu}(x)

SU(2): U(x+eps n, x) = 1 + i e eps n^\mu A_{mu}^i(x) \sigma^i/2

Wouldnt it be more convenient to use the same sign in both cases?

Rene.

Danny Ross Lunsford
Aug12-04, 08:29 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n\n\nmeyr2@web.de (Rene Meyer) wrote in message news:&lt;d664a6da.0408060603.7f415f60@posting.google. com&gt;...\n&gt; Hello,\n&gt;\n&gt; I was wondering if there is any physical reason or reason of\n&gt; convenience to use different signs in the comparators for QED gauge\n&gt; theory and YM theory, as Peskin/Schroeder do:\n&gt;\n&gt; U(1): U(x+eps n, x) = 1 - i e eps n^mu A_mu(x)\n&gt;\n&gt; SU(2): U(x+eps n, x) = 1 + i e eps n^mu A_mu^i(x) sigma^i/2\n&gt;\n&gt; Wouldnt it be more convenient to use the same sign in both cases?\n&gt;\n&gt; Rene.\n\nIt\'s just conventional, so that the electron charge comes out\nnegative, respecting historical usage.\n\n-drl\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">&nbsp;&nbsp;View this Usenet post in original ASCII form </a></div><P></jabberwocky>meyr2@web.de (Rene Meyer) wrote in message news:<d664a6da.0408060603.7f415f60@posting.google.com>...
> Hello,
>
> I was wondering if there is any physical reason or reason of
> convenience to use different signs in the comparators for QED gauge
> theory and YM theory, as Peskin/Schroeder do:
>
> U(1): U(x+eps n, x) = 1 - i e eps n^\mu A_{mu}(x)
>
> SU(2): U(x+eps n, x) = 1 + i e eps n^\mu A_{mu}^i(x) \sigma^i/2
>
> Wouldnt it be more convenient to use the same sign in both cases?
>
> Rene.

It's just conventional, so that the electron charge comes out
negative, respecting historical usage.

-drl