Quantum backreaction on a classical universe

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Abstract
We study a first-order formulation for the coupled evolution of a quantum scalar field and a classical Friedmann universe. The model is defined by a state dependent Hamiltonian constraint and the time dependent Schrödinger equation for the scalar field. We solve the resulting nonlinear equations numerically for initial data consisting of a Gaussian scalar field state and gravity phase space variables. This gives a self-consistent semiclassical evolution that includes nonperturbative “backreaction” due to particle production. We compare the results with the evolution of a quantum scalar field on a fixed background, and find that the backreaction modifies both particle production and cosmological expansion, and that these effects remain bounded.
Funding Information
  • Natural Sciences and Engineering Research Council of Canada
  • Indian Institute of Technology Delhi

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