Eur. Phys. J. C (2007) 49: 755-766
https://doi.org/10.1140/epjc/s10052-006-0150-1

Regular Article - Theoretical Physics

Pion propagation in real time field theory at finite temperature

¹ Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata, 700064, India
² Variable Energy Cyclotron Centre, 1/AF, Bidhannagar, Kolkata, 700064, India

^* e-mail: mallik@theory.saha.ernet.in

Received: 9 August 2006
Revised: 21 September 2006
Published online: 2 December 2006

Abstract

We describe how the thermal counterpart of a vacuum two-point function may be obtained in the real time formalism in a simple way by using directly the 2×2 matrices that different elements acquire in this formalism. Using this procedure we calculate the analytic (single component) thermal amplitude for the pion pole term in the ensemble average of two axial-vector currents to two loops in chiral perturbation theory. The general expressions obtained for the effective mass and the decay constants of the pion are evaluated in the chiral and the non-relativistic limits.