Does decoherence violate decoupling?

Abstract

Recent calculations in both flat and de Sitter spacetimes have highlighted a tension between the decoupling of high-energy physics from low-energy degrees of freedom and the expectation that quantum systems decohere due to interactions with unknown environments. In effective field theory (EFT), integrating out heavy fields should lead to Hamiltonian time evolution, which preserves the purity of low-energy states. This is consistent with the fact that we never observe isolated quantum states spontaneously decohering in the vacuum due to unknown high-energy physics. However, when a heavy scalar of mass $M$ is traced out, the resulting purity of a light scalar with mass $m$ typically appears to scale as a power of $1/M$ (when $m\ll M$), an effect that cannot be captured by a local effective Hamiltonian. We resolve this apparent paradox by showing that the purity depends on the resolution scale of the EFT and how the environment is traced out. We provide a practical method for diagnosing the purity of low-energy states consistent with EFT expectations, and briefly discuss some of the implications these observations have for how ultraviolet divergences can appear in decoherence calculations.

17 pages + appendices, 2 figures

References in corpus (31)

• Quantum Gravity in Everyday Life: General Relativity as an Effective Field Theory
• Keldysh Field Theory for Driven Open Quantum Systems
• Power-counting and the Validity of the Classical Approximation During Inflation
• Symplectic invariants, entropic measures and correlations of Gaussian states
• On Loops in Inflation
• Super-Hubble de Sitter Fluctuations and the Dynamical RG
• Proof of the Weak Gravity Conjecture from Black Hole Entropy
• Schwinger-Keldysh Diagrammatics for Primordial Perturbations
• The "in-in" Formalism and Cosmological Perturbations
• Entropy Bounds on Effective Field Theory from Rotating Dyonic Black Holes
• Entropy Bound and Unitarity of Scattering Amplitudes
• Minimal decoherence from inflation
• Benchmarking the cosmological master equations
• Positivity bounds on effective field theories with spontaneously broken Lorentz invariance
• Killing Horizons Decohere Quantum Superpositions
• The Open Effective Field Theory of Inflation
• Cosmological Consequences of Initial State Entanglement
• Quantum recoherence in the early universe
• Cosmic Purity Lost: Perturbative and Resummed Late-Time Inflationary Decoherence
• Effective field theory in time-dependent settings
• Decoherence out of fire: Purity loss in expanding and contracting universes
• On the Decoherence of Primordial Gravitons
• In-in formalism for the entropy of quantum fields in curved spacetimes
• On Entropy Growth in Perturbative Scattering
• Divergences in open quantum systems
• Local Description of Decoherence of Quantum Superpositions by Black Holes and Other Bodies
• Decoherence by warm horizons
• On $i\epsilon$ Prescription in Cosmology
• Decoherence of Cosmological Perturbations from Boundary Terms and the Non-Classicality of Gravity
• Cosmological Bell Tests with Decoherence Effects
• Decoherence due to the Casimir effect?

Cited by in corpus (3)

• The Massive Flat Space Limit of Cosmological Correlators
• Spin correlations and Bell nonlocality in $\Lambda \bar{\Lambda }$ pair production from $e^{+}{e}^{-}$ collisions with a thrust cut
• Entanglement features in scattering mediated by heavy particles