Quantum electrodynamics in two dimensions at a finite-temperature thermofield bosonization approach**The authors dedicate this work to the memory of Jorge André Swieca.

Abstract

The Schwinger model at finite temperature is analyzed using the thermofield dynamics formalism. The operator solution due to Lowenstein and Swieca is generalized to the case of finite temperature within the thermofield bosonization approach. The general properties of the statistical–mechanical ensemble averages of observables in the Hilbert subspace of gauge invariant thermal states are discussed. The bare charge and chirality of the Fermi thermofields are screened, giving rise to an infinite number of mutually orthogonal thermal ground states. One consequence of the bare charge and chirality selection rule at finite temperature is that there are innumerably many thermal vacuum states with the same total charge and chirality of the doubled system. The fermion charge and chirality selection rules at finite temperature turn out to imply the existence of a family of thermal theta-vacua states parametrized with the same number of parameters as in the zero temperature case.