# Effective field theory out of equilibrium: Brownian quantum fields

@article{Boyanovsky2015EffectiveFT, title={Effective field theory out of equilibrium: Brownian quantum fields}, author={Daniel Boyanovsky}, journal={New Journal of Physics}, year={2015}, volume={17} }

The emergence of an effective field theory out of equilibrium is studied in the case in which a light field—the system—interacts with very heavy fields in a finite temperature bath. We obtain the reduced density matrix for the light field, its time evolution is determined by an effective action that includes the influence action from correlations of the heavy degrees of freedom. The non-equilibrium effective field theory yields a Langevin equation of motion for the light field in terms of…

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## References

SHOWING 1-10 OF 85 REFERENCES

### Stochastic behavior of effective field theories across threshold

- Physics
- 1997

We explore how the existence of a field with a heavy mass influences the low energy dynamics of a quantum field with a light mass by expounding the stochastic characters of their interactions which…

### Quantum fluctuations, decoherence of the mean field, and structure formation in the early Universe.

- PhysicsPhysical review. D, Particles and fields
- 1995

It is shown that when the quantum to classical transition is properly treated, with due consideration of the relation of decoherence, noise, fluctuation and dissipation, the amplitude of density contrast predicted falls in the acceptable range without requiring a fine tuning of the coupling constant of the inflation field.

### Stochastic dynamics of correlations in quantum field theory: From the Schwinger-Dyson to Boltzmann-Langevin equation

- Physics
- 1999

The aim of this paper is twofold: to probe the statistical mechanical properties of interacting quantum fields, and to provide a field theoretical justification for a stochastic source term in the…

### Effective field theory in time-dependent settings

- Physics, Geology
- 2013

A bstractWe use the in-in or Schwinger-Keldysh formalism to explore the construction and interpretation of effective field theories for time-dependent systems evolving out of equilibrium. Starting…

### EFT beyond the horizon: stochastic inflation and how primordial quantum fluctuations go classical

- Physics
- 2014

A bstractWe identify the effective field theory describing the physics of super-Hubble scales and show it to be a special case of a class of effective field theories appropriate to open systems. Open…

### Equilibrium state of a self-interacting scalar field in the de Sitter background.

- PhysicsPhysical review. D, Particles and fields
- 1994

The stochastic approach is further developed to produce a method of calculating an arbitrary anomalously large correlation function of the scalar field in the de Sitter background, and expressions for the two-point correlation function in the equilibrium state, correlation time, and spatial physical correlation radius are presented.

### REAL-TIME RELAXATION AND KINETICS IN HOT SCALAR QED: LANDAU DAMPING

- Physics
- 1998

The real time evolution of non-equilibrium expectation values with soft length scales ∼ k −1 > (eT) −1 is solved in hot scalar electrodynamics, with a view towards understanding relaxational…

### Quantum kinetics and thermalization in a particle bath model.

- PhysicsPhysical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics
- 1999

A Markovian approximation that includes off-shell contributions and the usual Boltzmann equation (energy conserving) are obtained from the quantum kinetic equation in the limit of wide separation of time scales upon different coarse-graining assumptions.

### Quantum kinetic equation and cosmic pair annihilation

- Physics
- 1999

Pair annihilation of heavy stable particles that occurs in the early universe is investigated, and a quantum kinetic equation for the momentum distribution of the annihilating particle is derived,…

### Dissipation of quantum fields from particle creation.

- PhysicsPhysical review. D, Particles and fields
- 1989

This model illustrates that the appearance of dissipative behavior from the back reaction of particle creation in quantum fields is a general feature and suggests that the role of gravity in the display of dissipatives behavior in semiclassical processes is not unique.