Finite temperature fermionic condensate and currents in topologically nontrivial spaces

Abstract

We investigate the finite temperature fermionic condensate and the expectation values of the charge and current densities for a massive fermion field in a spacetime background with an arbitrary number of toroidally compactified spatial dimensions in the presence of a nonvanishing chemical potential. Periodicity conditions along compact dimensions are taken with arbitrary phases and the presence of a constant gauge field is assumed. The latter gives rise to Aharonov-Bohm-like effects on the expectation values. They are periodic functions of magnetic fluxes enclosed by compact dimensions with the period equal to the flux quantum. The current density has nonzero components along compact dimensions only. Both low- and high-temperature asymptotics of the expectation values are studied. In particular, it has been shown that at high temperatures the current density is exponentially suppressed. This behavior is in sharp contrast with the corresponding asymptotic in the case of a scalar field, where the current density linearly grows with the temperature. The features for the models in odd-dimensional spacetimes are discussed. Applications are given to cylindrical and toroidal nanotubes described within the framework of effective Dirac theory for the electronic subsystem.