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May 6, 2008

Around the Blogs

Probably everyone else knew, but I was pleased to learn that Dmitry Podolsky has a new blog. Dmitry’s main focus is on cosmology (he was a student of Starobinski), but his blog runs the gamut of subjects, and he’s been churning out posts of very high quality. His latest is on the limits of validity of cosmological perturbation theory, a subject which has seen several interesting papers, since I last blogged about it.

Adam FalkowskiJester has a scathing review of a CERN seminar/recent paper by John Moffat. Moffat wants to avoid introducing a Higgs (or other new degrees of freedom) into the Standard Model, by having the theory become nonlocal at a scale of about a TeV (more precisely, at Λ W=541.189\Lambda_W=541.189 GeV (!)). Nonlocality is a sort of magic pixie dust that makes all of the obvious problems go away. The scattering amplitude for longitudinal W-bosons grows like ss, violating the unitarity bound above a TeV or so? No problem: in Moffat’s nonlocal theory, the amplitude just vanishes for s1s\gtrsim 1 TeV. This, in turn, violates the Cerulus-Martin bound1, |A(s,cosθ)|e f(θ)slog(s)|A(s,\cos\theta)| \geq e^{-f(\theta)\sqrt{s}\log(s)}? Don’t worry …

I suppose I could go on in this vein, but someone will doubtless come along and accuse me of bias. Suffice to say that introducing nonlocality in some willy-nilly fashion like this is bad mojo. And, even were it totally unfair, Jester’s account is wittier than mine.

1 The bound requires analyticity of the elastic scattering amplitude in the cut z=cosθz=\cos\theta plane and its polynomial boundedness in ss. The latter, at least for forward scattering, is intimately connected with causality. In addition to local quantum field theory, both perturbative string scattering amplitudes and various conjectured nonperturbative extensions satisfy the Cerulus-Martin bound, though, to be fair, the latter conjecture violates polynomial boundedness, which is rather suspicious.

Posted by distler at May 6, 2008 11:01 PM

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Re: Around the Blogs

Apropos new blogs, Sunil Mukhi has a blog: tantu-jaal.

Posted by: Matthias on May 8, 2008 12:22 AM | Permalink | Reply to this

Re: Around the Blogs

Moffat’s slides at say on page 66 that the cross section slowly starts going down to zero above 2 TeV. Nowehere does he say that the cross section is exactly zero.


Posted by: Greg on July 9, 2009 7:28 AM | Permalink | Reply to this

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