Dynamical Symmetry and the Thermofield State at Large <i>N</i>

Abstract

We discuss thermofield double QFT at real time, in the large N limit. First, we establish a (dynamical) symmetry, which we argue holds in general for the real-time portion of the Schwinger–Kelydish contour. At large N, this symmetry is seen to generate a one-parameter degeneracy of stationary collective solutions. The construction is explicitly worked out on an example of the O(N) vector QFT. As a nontrivial application, we describe the construction of the corresponding (large N) thermofield double state in real-time collective formalism.

Keywords

• thermofield double state
• large <i>N</i>
• collective field theory
• <i>O(N)</i> vector model