Estimates for the Boltzmann collision operator via radial symmetry and Fourier transform

We extend the L(P)-theory of the Boltzmann collision operator by using classical techniques based in the Carlerman representation and Fourier analysis, allied to new ideas that exploit the radial symmetry of this operator. We are then able to greatly simplify existent technical proofs in this theory, extend the range, and obtain explicit sharp constants in some convolution-like inequalities for the gain part of the Boltzmann collision operator. (C) 2009 Elsevier Inc. All rights reserved.