tag:blogger.com,1999:blog-8883034.post6974444289059931480..comments2023-11-01T08:46:31.962+01:00Comments on atdotde: Instability of the QED vacuum at large fine structure constantRoberthttp://www.blogger.com/profile/06634377111195468947noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-8883034.post-82064144677397650972010-07-01T11:06:02.718+02:002010-07-01T11:06:02.718+02:00James, you are right. At least for part of the sto...James, you are right. At least for part of the story. <br /><br />Strictly speaking, what I discuss for most part of the post is not really QED but a (relativistic) theory of quantized electrons that interact via a <i>classical</i> electromagnetic interaction (except for the last part where I mention the running coupling). This is a better approximation for QED than for QCD.<br /><br />For QCD, I guess, its asymptotic safety that saves the day (physically speaking): At long distances there is no 1/r potential (that was my starting point) and at short distances the interaction becomes weak and the problem goes away. The cross over should be around the QCD scale and with the condensate this is exctly what one finds.Roberthttps://www.blogger.com/profile/06634377111195468947noreply@blogger.comtag:blogger.com,1999:blog-8883034.post-11997139737260215692010-07-01T10:53:05.460+02:002010-07-01T10:53:05.460+02:00Can I ask, if this is a problem for QED, why isn&#...Can I ask, if this is a problem for QED, why isn't it a problem for QCD, which does have alpha~1. Isn't this just the QCD quark condensate?Jamesnoreply@blogger.comtag:blogger.com,1999:blog-8883034.post-33350790518412447112010-02-10T19:54:49.880+01:002010-02-10T19:54:49.880+01:00A relevant review paper is
" Quantum mechan...A relevant review paper is <br /><br />" Quantum mechanics, the stability of matter and quantum electrodynamics"<br />Elliott H. Lieb, math-ph/0401004.<br /><br />Apparently the vacuum is indeed unstable for \alpha > 2.72.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8883034.post-72289337047577746382010-02-10T14:43:28.740+01:002010-02-10T14:43:28.740+01:00Also, I remember a short physreview paper, about o...Also, I remember a short physreview paper, about one page, about the stability and/or convergence of coupling constant expansion in QED. <br /><br />Very famous, but I can not remember the author.Alejandro Riverohttps://www.blogger.com/profile/16181521111080562335noreply@blogger.comtag:blogger.com,1999:blog-8883034.post-2776260960642525272010-01-22T20:01:14.659+01:002010-01-22T20:01:14.659+01:00This instability is of course most clearly express...This instability is of course most clearly expressed in the imaginary part of the Euler Heisenberg Lagrangian for the photon field. Attemps to see the effect in collsions of e.g. two U nuclei have failed so far.antinhttps://www.blogger.com/profile/16414021577545220874noreply@blogger.com