Quantum decoherence during inflation from gravitational nonlinearities
- 1 March 2016
- journal article
- Published by IOP Publishing in Journal of Cosmology and Astroparticle Physics
- Vol. 2016 (3), 022
- https://doi.org/10.1088/1475-7516/2016/03/022
Abstract
We study the inflationary quantum-to-classical transition for the adiabatic curvature perturbation ζ due to quantum decoherence, focusing on the role played by squeezed-limit mode couplings. We evolve the quantum state Ψ in the Schrödinger picture, for a generic cubic coupling to additional environment degrees of freedom. Focusing on the case of minimal gravitational interactions, we find the evolution of the reduced density matrix for a given long-wavelength fluctuation by tracing out the other (mostly shorter-wavelength) modes of ζ as an environment. We show that inflation produces phase oscillations in the wave functional Ψ[ζ(x)], which suppress off-diagonal components of the reduced density matrix, leaving a diagonal mixture of different classical configurations. Gravitational nonlinearities thus provide a minimal mechanism for generating classical stochastic perturbations from inflation. We identify the time when decoherence occurs, which is delayed after horizon crossing due to the weak coupling, and find that Hubble-scale modes act as the decohering environment. We also comment on the observational relevance of decoherence and its relation to the squeezing of the quantum state.Keywords
This publication has 44 references indexed in Scilit:
- Why do Cosmological Perturbations Look Classical to Us?Advanced Science Letters, 2009
- Semiclassicality and decoherence of cosmological perturbationsClassical and Quantum Gravity, 1996
- Inflation and squeezed quantum statesPhysical Review D, 1994
- On the quantum state of relic gravitonsClassical and Quantum Gravity, 1989
- Dynamics of phase transition in the new inflationary universe scenario and generation of perturbationsPhysics Letters B, 1982
- Fluctuations in the New Inflationary UniversePhysical Review Letters, 1982
- The development of irregularities in a single bubble inflationary universePhysics Letters B, 1982
- Cosmology for Grand Unified Theories with Radiatively Induced Symmetry BreakingPhysical Review Letters, 1982
- A new inflationary universe scenario: A possible solution of the horizon, flatness, homogeneity, isotropy and primordial monopole problemsPhysics Letters B, 1982
- Inflationary universe: A possible solution to the horizon and flatness problemsPhysical Review D, 1981