View Full Version : Electron positron annihilation related to string theory
FrediFizzx
May28-04, 02:01 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>I was wondering how string theory deals with e+e- annihilation or the\nannihilation of any pair. If the electron and positron are represented by\nstrings, do the strings just disappear forever when they annihilate?\n\nFrediFizzx\n\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"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>I was wondering how string theory deals with e+e- annihilation or the
annihilation of any pair. If the electron and positron are represented by
strings, do the strings just disappear forever when they annihilate?
FrediFizzx
Robert C. Helling
May28-04, 05:55 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>On Fri, 28 May 2004 02:01:34 -0400, FrediFizzx <fredifizzx@hotmail.com> wrote:\n> I was wondering how string theory deals with e+e- annihilation or the\n> annihilation of any pair. If the electron and positron are represented by\n> strings, do the strings just disappear forever when they annihilate?\n\nNo. As in QED, they will send out at least to photons to satisfy\nenergy momentum conservation. Thus this process is at leading order a\npair of pants diagram (or better its open string analogue) with the\ntwo incoming strings being in the electron mode and the two outgoing\nstring in the gauge boson mode.\n\nRobert\n\n--\n..oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oO o.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oO\nRobert C. Helling Department of Applied Mathematics and Theoretical Physics\nUniversity of Cambridge\nprint "Just another Phone: +44/1223/766870\nstupid .sig\\n"; http://www.aei-potsdam.mpg.de/~helling\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"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>On Fri, 28 May 2004 02:01:34 -0400, FrediFizzx <fredifizzx@hotmail.com> wrote:
> I was wondering how string theory deals with e+e- annihilation or the
> annihilation of any pair. If the electron and positron are represented by
> strings, do the strings just disappear forever when they annihilate?
No. As in QED, they will send out at least to photons to satisfy
energy momentum conservation. Thus this process is at leading order a
pair of pants diagram (or better its open string analogue) with the
two incoming strings being in the electron mode and the two outgoing
string in the gauge boson mode.
Robert
--
..oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo. oOo.oOo.oOo.oOo.oOo.oOo.oOo.oO
Robert C. Helling Department of Applied Mathematics and Theoretical Physics
University of Cambridge
print "Just another Phone: +44/1223/766870
stupid .sig\n"; http://www.aei-potsdam.mpg.de/~helling
Urs Schreiber
May28-04, 06:26 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>On Fri, 28 May 2004, Robert C. Helling wrote:\n\n> On Fri, 28 May 2004 02:01:34 -0400, FrediFizzx <fredifizzx@hotmail.com> wrote:\n> > I was wondering how string theory deals with e+e- annihilation or the\n> > annihilation of any pair. If the electron and positron are represented by\n> > strings, do the strings just disappear forever when they annihilate?\n>\n> No. As in QED, they will send out at least to photons to satisfy\n> energy momentum conservation. Thus this process is at leading order a\n> pair of pants diagram (or better its open string analogue) with the\n> two incoming strings being in the electron mode and the two outgoing\n> string in the gauge boson mode.\n\nOn the other hand, you certainly can have processes in which the string\nsort of "disappears", namely for instance in pure loop diagrams, if that\'s\nwhat Fredi is concerned about.\n\nMaybe the following general statement helps Fredi to think about this\nstuff:\n\nGiving any Feynman diagram of some field theory, one can imagine that it\nis the approximation to a 2-d surface which would be obtained by blowing\nup the infinitesimally thin edges and vertices of the Feynman diagram, so\nthat for instance, as Robert has mentioned, the trivalent vertex\n\n/\n/\n-----<\n\\\n\\\n\n\nbecomes the "pair of pants" (for closed strings) or something like\n\n\n/ /\n/ /\n------/ /\n\\\n------\\ \\\n\\ \\\n\\\n\n\nfor open strings. See for instance figure 2 of\n\nvan Proeyen\nIntroduction to string theory\nhttp://itf.fys.kuleuven.ac.be/~toine/IITSStrings.pdf\n\nfor better illustration.\n\nIn particular, if we have Feynman diagrams like\n\n\n/\\\n/ \\\n/ \\\n\\ /\n\\ /\n\\/\n\nwhere particles "appear and disappear" this corresponds to the torus\n(closed string) or the annulus=disc with a puncture (open string)\nworldsheet (in the oriented case) or even the Klein bottle and the Moebius\nstrip (in the unoriented case).\n\nSo in this sense I believe that it is fair to say that strings can\n"appear and disappear".\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"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>On Fri, 28 May 2004, Robert C. Helling wrote:
> On Fri, 28 May 2004 02:01:34 -0400, FrediFizzx <fredifizzx@hotmail.com> wrote:
> > I was wondering how string theory deals with e+e- annihilation or the
> > annihilation of any pair. If the electron and positron are represented by
> > strings, do the strings just disappear forever when they annihilate?
>
> No. As in QED, they will send out at least to photons to satisfy
> energy momentum conservation. Thus this process is at leading order a
> pair of pants diagram (or better its open string analogue) with the
> two incoming strings being in the electron mode and the two outgoing
> string in the gauge boson mode.
On the other hand, you certainly can have processes in which the string
sort of "disappears", namely for instance in pure loop diagrams, if that's
what Fredi is concerned about.
Maybe the following general statement helps Fredi to think about this
stuff:
Giving any Feynman diagram of some field theory, one can imagine that it
is the approximation to a 2-d surface which would be obtained by blowing
up the infinitesimally thin edges and vertices of the Feynman diagram, so
that for instance, as Robert has mentioned, the trivalent vertex
/
/
-----<
\
\
becomes the "pair of pants" (for closed strings) or something like
/ // /
------/ /
\
------\ \\ \
\
for open strings. See for instance figure 2 of
van Proeyen
Introduction to string theory
http://itf.fys.kuleuven.ac.be/~toine/IITSStrings.pdf
for better illustration.
In particular, if we have Feynman diagrams like
/\
/ \/ \\ /\ /
\/
where particles "appear and disappear" this corresponds to the torus
(closed string) or the annulus=disc with a puncture (open string)
worldsheet (in the oriented case) or even the Klein bottle and the Moebius
strip (in the unoriented case).
So in this sense I believe that it is fair to say that strings can
"appear and disappear".
FrediFizzx
May29-04, 04:56 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>"Urs Schreiber" <Urs.Schreiber@uni-essen.de> wrote in message\nnews:Pine.LNX.4.31.0405280610510.28118-100000@kaluza.harvard.edu...\n| On Fri, 28 May 2004, Robert C. Helling wrote:\n|\n| > On Fri, 28 May 2004 02:01:34 -0400, FrediFizzx <fredifizzx@hotmail.com>\nwrote:\n| > > I was wondering how string theory deals with e+e- annihilation or the\n| > > annihilation of any pair. If the electron and positron are\nrepresented by\n| > > strings, do the strings just disappear forever when they annihilate?\n| >\n| > No. As in QED, they will send out at least to photons to satisfy\n| > energy momentum conservation. Thus this process is at leading order a\n| > pair of pants diagram (or better its open string analogue) with the\n| > two incoming strings being in the electron mode and the two outgoing\n| > string in the gauge boson mode.\n|\n| On the other hand, you certainly can have processes in which the string\n| sort of "disappears", namely for instance in pure loop diagrams, if that\'s\n| what Fredi is concerned about.\n\nWell, actually I was more concerned about what Robert mentioned. Which I\nknew and forgot. This tired old mind just has a hard time keeping track of\nall this stuff. ;-)\n\n| So in this sense I believe that it is fair to say that strings can\n| "appear and disappear".\n\nI sure do have trouble with this "appear and disappear". Seems like we need\nanother space for things (entities?) to appear from and disappear to.\n\nFrediFizzx\n\n[Moderator\'s note: Quoted text trimmed by moderator. -usc]\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"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Urs Schreiber" <Urs.Schreiber@uni-essen.de> wrote in message
news:Pine.LNX.4.31.0405280610510.28118-100000@kaluza.harvard.edu...
| On Fri, 28 May 2004, Robert C. Helling wrote:
|
| > On Fri, 28 May 2004 02:01:34 -0400, FrediFizzx <fredifizzx@hotmail.com>
wrote:
| > > I was wondering how string theory deals with e+e- annihilation or the
| > > annihilation of any pair. If the electron and positron are
represented by
| > > strings, do the strings just disappear forever when they annihilate?
| >
| > No. As in QED, they will send out at least to photons to satisfy
| > energy momentum conservation. Thus this process is at leading order a
| > pair of pants diagram (or better its open string analogue) with the
| > two incoming strings being in the electron mode and the two outgoing
| > string in the gauge boson mode.
|
| On the other hand, you certainly can have processes in which the string
| sort of "disappears", namely for instance in pure loop diagrams, if that's
| what Fredi is concerned about.
Well, actually I was more concerned about what Robert mentioned. Which I
knew and forgot. This tired old mind just has a hard time keeping track of
all this stuff. ;-)
| So in this sense I believe that it is fair to say that strings can
| "appear and disappear".
I sure do have trouble with this "appear and disappear". Seems like we need
another space for things (entities?) to appear from and disappear to.
FrediFizzx
[Moderator's note: Quoted text trimmed by moderator. -usc]
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