Arcadian Functor

occasional meanderings in physics' brave new world

My Photo
Location: New Zealand

Marni D. Sheppeard

Thursday, July 12, 2007

GRG18 4a

Two fantastic talks in the Quantum Cosmology session this afternoon. First, Mairi Sakellariadou spoke about inflation in Loop Quantum Cosmology. Gibbons et al showed some time ago that in FRW (ie. classically) the probability of inflation onset goes as exp(-3N) where N is the number of e-foldings. In other words, it is exponentially unlikely. The LQC analysis offers the possibility of corrections to the exponent which might greatly increase the likelihood of inflation, but this was shown to be the case only for <20 e-foldings, so even in LQC inflation is highly unlikely, and so it appears that inflation (if it exists at all - er, yeah, right) can only be addressed fully within a proper theory of QG.

Warner Miller took a quantum computational point of view on QG: good man. He was analysing lattices built from quantum circuit information flows embedded in spacetimes with Regge calculus. The really beautiful thing was his way of factorising this calculus using Voronoi duals to the lattice, representing matter information content. So pure QG is non-sensical here, which is as it should be physically. The potentials for matter are encoded in the quantum gates. Moreover, it seems one can directly interpret the duality in terms of a principle of quantum general covariance. Miller also mentioned theorems of Cheeger et al which recover curved manifolds from the discrete Regge triangulations, so there is every reason to believe that the continuum theory behaves as desired.


Post a Comment

<< Home