Schwinger-Keldysh formalism II: Thermal equivariant cohomology

Understand

Causally ordered correlation functions of local operators in near-thermal quantum systems computed using the Schwinger-Keldysh formalism obey a set of Ward identities.

• These can be understood rather simply as the consequence of a topological (BRST) algebra, called the universal Schwinger-Keldysh superalgebra, as explained in our companion paper arXiv:1610.01940.
• In the present paper we provide a mathematical discussion of this topological algebra.
• In particular, we argue that the structures can be understood in the language of extended equivariant cohomology.