A general nonlinear sigma model can be expressed as S[g]=1λ∫ddr tr[▽g▽g−1]
where
g takes value in a matrix representation of some compact Lie group
G. Usual renormalization group analysis of the model starts with the Callan-Symanzik equation (see e.g.
Quantum Field Theory and Critical Phenomena by Zinn-Justin). However, I am wondering how the Wilson's approach works. How to decompose
g to a part for fast modes and a part for slow modes? Discussion of the approach can be found in Sec. 8.5 of
Condensed Matter Field Theory by Altland and Simons, but I am confused by the statement
g(r)=gs(r)gf(r). How can we do that? How is a Fourier transform of a matrix-represented compact lie group defined?
A hint is given by A. Polyakov in Chapter 2 of his book Gauge Fields and Strings, where he decomposes g(r) as h(r)⋅gcl(r) with gcl(r) some classical solution to the Lagrangian. But I cannot get the brief explanation though.
In Altland and Simons, their idea is to write g=eiW. W is the Lie algebra. Then the fast and the slow components are referring to W.
Some related unanswered questions on Physics StackExchange can be found here and here.
This post imported from StackExchange Physics at 2014-12-18 12:35 (UTC), posted by SE-user L. Su