### 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 Falkowski~~Jester 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 $\Lambda_W=541.189$ 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 $s$, violating the unitarity bound above a TeV or so? No problem: in Moffat’s nonlocal theory, the amplitude just *vanishes* for $s\gtrsim 1$ TeV. This, in turn, violates the Cerulus-Martin bound^{1}, $|A(s,\cos\theta)| \geq e^{-f(\theta)\sqrt{s}\log(s)}$? 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 $z=\cos\theta$ plane and its polynomial boundedness in $s$. 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.

## Re: Around the Blogs

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