Schwinger terms and cyclic cohomology for massive 1+1-dimensional fermions and Virasoro algebras

Abstract

An important example of characters on two-summable Fredholm modules are Schwinger terms arising in the commutators between charge and axial-charge operators. 1+1-dimensional massive fermions are discussed using the language of quasifree second quantization and for a large class of models the usual δ′-Schwinger term is obtained. The results confirm calculations within the massive Schwinger model at finite temperature but disagree with a conjecture concerning anomaly meltdown. The dependence of the Virasoro cocycle in the quasifree second-quantization framework on traceclass perturbations (like charging and thermalizing) are also investigated.