Thermalization of overpopulated systems in the 2PI formalism

Shoichiro Tsutsui (1) , Jean-Paul Blaizot (2, 3) , Yoshitaka Hatta (3)

1 Department of Physics [Kyoto]
2 IPHT - Institut de Physique Théorique - UMR CNRS 3681
3 YITP - Yukawa Institute for Theoretical Physics [Kyoto]

Based on the two-particle irreducible (2PI) formalism to next-to-leading order in the $1/N$ expansion, we study the thermalization of overpopulated systems in scalar $O(N)$ theories with moderate coupling. We focus in particular on the growth of soft modes, and examine whether this can lead to the formation of a transient Bose-Einstein condensate (BEC) when the initial occupancy is high enough. For the value of the coupling constant used in our simulations, we find that while the system rapidly approaches the condensation threshold, the formation of a BEC is eventually hindered by particle number changing processes.

Mots clés: field theory: scalar; field theory: finite temperature; O(N); expansion 1/N; effect: higher-order; higher-order: 1; condensation: Bose-Einstein; particle number: conservation law

Domaines: Gaz Quantiques [cond-mat.quant-gas]; Physique Nucléaire Théorique [nucl-th]

Shoichiro Tsutsui, Jean-Paul Blaizot, Yoshitaka Hatta. Thermalization of overpopulated systems in the 2PI formalism. Physical Review D, 2017, 96, pp.036004. ⟨10.1103/PhysRevD.96.036004⟩. ⟨cea-01543664v2⟩