Finite-temperature quantum field theory incorporates thermal effects through formalisms like imaginary-time Matsubara frequencies or real-time dynamics, distinguishing it fundamentally from zero-temperature formulations.
The claim states that quantum field theory at finite temperature differs fundamentally from zero temperature, which is a foundational and defining premise of thermal field theory (utilizing distinct formalisms such as partition functions and thermal Green's functions). Because this is a well-established foundational fact by definition and everyday application in theoretical physics, no specific citation is needed, classifying the claim as common knowledge in the context of the domain.