Sigma model effective action for strong localization

TL;DR

This paper derives a sigma model effective action for a Bose gas in a random field, enabling analysis of its properties under strong fluctuations, which advances understanding of localization phenomena in disordered quantum systems.

Contribution

It introduces a sigma model effective action applicable to both weak and strong random fields, providing a new tool for studying localization in Bose gases.

Findings

Effective action derived for strong and weak disorder regimes

Analysis of Bose gas properties under strong random field fluctuations

Framework applicable to irreversible quantum processes

Abstract

Bose gas in a random external field is considered. The sigma model like effective action both for weak and strong random fields compared with the interaction between particles is derived by averaging over the random field and integration over the quantum fluctuations in the framework of the Keldysh-Schwinger technique for irreversible processes. Using this effective action the properties of the system in strongly fluctuating random field are analyzed.