Ground State and QFT. [Archive]

Dec14-04, 10:18 AM

Arnold Neumaier

Dec17-04, 07:49 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>MM wrote:\n> Arnold Neumaier wrote:\n>\n> > A free field has no Unruh effect since there are no interactions.\n>\n> Hmmm. I wasn\'t aware that the Unruh effect depended on\n> interactions. Looking at the (admittedly simplified)\n> derivation in quant-ph/0401170, they just take the\n> usual SR transformation formula for uniform acceleration\n> and apply it to the (free) field operators, if I\'m\n> reading the paper correctly.\n\nIn a universe governed by free field equations there cannot\nbe accelerated observers. Of course, you can consider what happens\nto a ficticious observer not restricted by equations of motion,\nand then an accelerated observer sees an Unruh effect even in a\nfree field theory. To have _real_ accelerations you need interactions\nproviding the forces to accelerate, and then all sorts of unsolved\nquestions appear. I don\'t understand enough to discuss it with\nauthority.\n\n\nArnold Neumaier\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>MM wrote:
> Arnold Neumaier wrote:
>
> > A free field has no Unruh effect since there are no interactions.
>
> Hmmm. I wasn't aware that the Unruh effect depended on
> interactions. Looking at the (admittedly simplified)
> derivation in http://www.arxiv.org/abs/quant-ph/0401170, they just take the
> usual SR transformation formula for uniform acceleration
> and apply it to the (free) field operators, if I'm
> reading the paper correctly.

In a universe governed by free field equations there cannot
be accelerated observers. Of course, you can consider what happens
to a ficticious observer not restricted by equations of motion,
and then an accelerated observer sees an Unruh effect even in a
free field theory. To have _real_ accelerations you need interactions
providing the forces to accelerate, and then all sorts of unsolved
questions appear. I don't understand enough to discuss it with
authority.

Arnold Neumaier