Semiclassical Backreaction: A Qualitative Assessment
arXiv:2411.19825 · doi:10.1103/PhysRevD.111.065008
Abstract
The backreaction of quantum degrees of freedom on classical backgrounds is a poorly understood topic in theoretical physics. Most often it is treated within the semiclassical approximation with the help of various ad hoc prescriptions accounting for the effect of quantum excitations on the dynamics of the background. We focus on two popular ones: (i) the mean-field approximation whereby quantum degrees of freedom couple to the classical background via their quantum expectation values; (ii) the (stochastic) Truncated Wigner method whereby the fully coupled system is evolved using classical equations of motion for various randomly sampled initial conditions of the quantum degree of freedom, and a statistical average is performed a posteriori. We evaluate the performance of each method in a simple toy model against a fully quantum mechanical treatment, and identify its regime of validity. We interpret the results in terms of quantum entanglement and loss of classicality of the background.
v1: 34 pages, 9 figures; V2: Added discussion about entanglement entropy and an appendix concerning systems with more modes
References in corpus (36)
- Quantum entanglement
- Towards the Theory of Reheating After Inflation
- General relativity as an effective field theory: The leading quantum corrections
- Nonperturbative Dynamics Of Reheating After Inflation: A Review
- Decoherence, Chaos, and the Second Law
- The truncated Wigner method for Bose condensed gases: limits of validity and applications
- Gravitational Bose-Einstein condensation in the kinetic regime
- Effective Equations of Motion for Quantum Systems
- Stochastic Gravity: Theory and Applications
- Quantum Break-Time of de Sitter
- Quantum Radiation of Oscillons
- Cosmological Particle Production: A Review
- Backreaction in Semiclassical Cosmolgy: The Einstein Langevin Equation
- The art of simulating the early Universe -- Part I
- Quantum Breaking Bound on de Sitter and Swampland
- Scrambling in the Black Hole Portrait
- Linear growth of the entanglement entropy and the Kolmogorov-Sinai rate
- High-order quantum back-reaction and quantum cosmology with a positive cosmological constant
- A New Semiclassical Picture of Vacuum Decay
- Entropy Bound and Unitarity of Scattering Amplitudes
- Classicality and Quantum Break-Time for Cosmic Axions
- Effective potentials from semiclassical truncations
- Back-reaction on background fields: a coherent state approach
- A Classical-Quantum Correspondence and Backreaction
- Classical-Quantum Correspondence for Fields
- Faithful realizations of semiclassical truncations
- Quantum Evaporation of Classical Breathers
- Canonical description of cosmological backreaction
- The Timescales of Quantum Breaking
- On the quantum stability of Q-balls
- On Evolution of Coherent States as Quantum Counterpart of Classical Dynamics
- Kink-antikink scattering in a quantum vacuum
- Perturbative Understanding of Non-Perturbative Processes and Quantumization versus Classicalization
- Background Field Method and Initial-Time Singularity for Coherent States
- Quantum Backreaction on Classical Dynamics
- Canonical description of quantum dynamics