What does Landau mean? (From D. Gross Lecture) [Archive]

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lost.and.lonely.physicist@gmail.com

Mar30-05, 02:03 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>I browsed through David Gross\' Nobel lecture slides (URL below) and\nnoticed the following quote of Landau (1960):\n\n"We reach the conclusion that within the limits of formal\nelectrodynamics a point interaction is equivalent, for any intensity\nwhatever, to no interaction at all. We are driven to the conclusion\nthat the Hamiltonian method for strong interaction is dead and must be\nburied, although of course with deserved honor."\n\nWhat does Landau mean? The N-point function seems to be based on the\nintegral of the Hamiltonian density, time-ordered and exponentiated,\nno?\n\nhttp://nobelprize.org/physics/laureates/2004/gross-slides.pdf\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 browsed through David Gross' Nobel lecture slides (URL below) and
noticed the following quote of Landau (1960):

"We reach the conclusion that within the limits of formal
electrodynamics a point interaction is equivalent, for any intensity
whatever, to no interaction at all. We are driven to the conclusion
that the Hamiltonian method for strong interaction is dead and must be
buried, although of course with deserved honor."

What does Landau mean? The N-point function seems to be based on the
integral of the Hamiltonian density, time-ordered and exponentiated,
no?

http://nobelprize.org/physics/laureates/2004/gross-slides.pdf

Aaron Bergman

Mar31-05, 12:54 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>In article <1112134861.661354.118980@g14g2000cwa.googlegroups .com>,\n"lost.and.lonely.physicist@gmail.com"\n<lo st.and.lonely.physicist@gmail.com> wrote:\n\n> I browsed through David Gross\' Nobel lecture slides (URL below) and\n> noticed the following quote of Landau (1960):\n>\n> "We reach the conclusion that within the limits of formal\n> electrodynamics a point interaction is equivalent, for any intensity\n> whatever, to no interaction at all. We are driven to the conclusion\n> that the Hamiltonian method for strong interaction is dead and must be\n> buried, although of course with deserved honor."\n>\n> What does Landau mean?\n\nWithout hearing the context, I\'d guess that the reference is to the\nLandau pole. The only way to avoid it is to set the interaction equal to\nzero.\n\nI think I remember hearing that Landau discovered the \'Landau pole\' in a\nmanner different than we do it today, but I\'m guessing the effect -- bad\nstuff unless the interaction is zero -- is the same.\n\nAaron\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>In article <1112134861.661354.118980@g14g2000cwa.googlegroups. com>,
"lost.and.lonely.physicist@gmail.com"
<lost.and.lonely.physicist@gmail.com> wrote:

> I browsed through David Gross' Nobel lecture slides (URL below) and
> noticed the following quote of Landau (1960):
>
> "We reach the conclusion that within the limits of formal
> electrodynamics a point interaction is equivalent, for any intensity
> whatever, to no interaction at all. We are driven to the conclusion
> that the Hamiltonian method for strong interaction is dead and must be
> buried, although of course with deserved honor."
>
> What does Landau mean?

Without hearing the context, I'd guess that the reference is to the
Landau pole. The only way to avoid it is to set the interaction equal to
zero.

I think I remember hearing that Landau discovered the 'Landau pole' in a
manner different than we do it today, but I'm guessing the effect -- bad
stuff unless the interaction is zero -- is the same.

Aaron

Arnold Neumaier

Mar31-05, 09:42 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>lost.and.lonely.physicist@gmail.com wrote:\n> I browsed through David Gross\' Nobel lecture slides (URL below) and\n> noticed the following quote of Landau (1960):\n>\n> "We reach the conclusion that within the limits of formal\n> electrodynamics a point interaction is equivalent, for any intensity\n> whatever, to no interaction at all. We are driven to the conclusion\n> that the Hamiltonian method for strong interaction is dead and must be\n> buried, although of course with deserved honor."\n\nI think that was an understandable assessment before gauge fields were\nfound to account for the strong interaction. Note that this statement\nis from 1960.\n\nQED is problaby considered to have \'for any intensity whatever,\nno interaction at all\' just because its effects are so tiny\ncompared to strong interactions.\n\n\nArnold Neumaier\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>lost.and.lonely.physicist@gmail.com wrote:
> I browsed through David Gross' Nobel lecture slides (URL below) and
> noticed the following quote of Landau (1960):
>
> "We reach the conclusion that within the limits of formal
> electrodynamics a point interaction is equivalent, for any intensity
> whatever, to no interaction at all. We are driven to the conclusion
> that the Hamiltonian method for strong interaction is dead and must be
> buried, although of course with deserved honor."

I think that was an understandable assessment before gauge fields were
found to account for the strong interaction. Note that this statement
is from 1960.

QED is problaby considered to have 'for any intensity whatever,
no interaction at all' just because its effects are so tiny
compared to strong interactions.

Arnold Neumaier