The exact mass gap of the O(N) σmodel for arbitrary N >= 3 in d = 2
Abstract
Starting from the exact Smatrix of the O(N) model we derive an integral equation, which determines the free energy as the function of the chemical potential coupled to a Noether charge. For N = 3 and 4 the equation agrees with that obtained earlier by Polyakov and Wiegmann with Bethe Ansatz for the related fermionic models. Using a method discussed in a recent paper by M. Maggiore and the authors, this integral equation predicts for the mass gap m = (8/e)^{1/(N2)} × [1/Γ (1 + 1/(N  2))] Λ_{MS}.
On leave of absence from Institute for Theoretical Physics, Eötvös University, H1088 Budapest 8, Hungary.
 Publication:

Physics Letters B
 Pub Date:
 August 1990
 DOI:
 10.1016/03702693(90)90686Z
 Bibcode:
 1990PhLB..245..529H