Exact effective action for [(1+1)-dimensional] fermions in an Abelian background at finite temperature - art. no. 105011

In an effort to further understand the structure of effective actions for f ermions in an external gauge background at finite temperature, we study the example of (1 + 1)-dimensional fermions interacting with an arbitrary Abel ian gauge field. We evaluate the effective action exactly at finite tempera ture. This effective action is non-analytic as is expected at finite temper ature. However, contrary to the structure at zero temperature and contrary to naive expectations, the effective action at finite temperature has inter actions to all (even) orders (which, however, do not lead to any quantum co rrections). The covariant structure thus obtained may prove useful in study ing (2 + 1)-dimensional models in arbitrary backgrounds. We also comment br iefly on the solubility of various (1 + 1)-dimensional models at finite tem perature. [S0556-2821(99)03410-3].