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, we introduce a general Keldysh action that maximally obeys Weinbergian constraints, including locality, Poincar\'e invariance, and two ``
CPT'' constraints: complete positivity and trace preserving as well as charge, parity, and time reversal symmetry. 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 $\mathrm{\ensuremath{\Delta}}<d/2$ or UV when $\mathrm{\ensuremath{\Delta}}>d/2$ given
d the dimensions of spacetime and $\mathrm{\ensuremath{\Delta}}$ 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. Examples including a $(0+1)\text{\ensuremath{-}}d$ harmonic oscillator under continuous measurement and a $(4\ensuremath{-}\ensuremath{\epsilon})\text{\ensuremath{-}}d$ classic
O(N) vector model with quartic interactions are studied.
We rigorously analyze the nonequilibrium thermodynamic behavior of various formulations of quantum Brownian motion using the framework of stochastic thermodynamics. While the widely used Caldeira-Leggett master equation exhibits desirable thermodynamic features—such as the fulfillment of a detailed balance—it fails to ensure complete positivity. In contrast, several completely positive and trace-preserving extensions turn out to be thermodynamically controversial. We show that such extensions introduce anomalous phase-space structures that violate detailed balance at the steady state, leading to nonvanishing entropy production and spurious nonequilibrium currents lacking a clear physical interpretation. Our results highlight a fundamental tension between quantum consistency and thermodynamic equilibration in open quantum systems.