Double-trace deformation in Keldysh field theory

The Keldysh formalism is capable of describing driven-dissipative dynamics of open quantum systems as nonunitary effective field theories that are not necessarily thermodynamical, thus often exhibiting new physics. Here, given a general Keldysh action, we find that the perturbative Lindblad term responsible for driven-dissipative dynamics introduced therein has the natural form of a double-trace deformation O², which, in the large N limit, possibly leads to a new nonthermal conformal fixed point. This fixed point is IR when Δd/2, given d the dimensions of spacetime and Δ the scaling dimension of O. Such a UV fixed point being not forbidden by Weinbergian constraints may suggest its existence and even completion of itself, in contrast to the common sense that dissipation effects are always IR relevant. This observation implies that driven-dissipative dynamics is much richer than thermodynamics, differing in not only its noncompliance with thermodynamic symmetry (e.g., the fluctuation-dissipation relation) but its UV/IR relevance as well. In particular, our results pave a new path that brings the Keldysh formalism to the gravitational side under the pronounced holographic AdS/CFT correspondence. This may lead to a refreshing perspective of how a Keldysh CFT living on the boundary corresponds to the bulk theory.