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Special cosmological models derived from the semiclassical Einstein equation on flat FLRW space-times. (English) Zbl 1496.83002

Summary: This article presents numerical work on a special case of the cosmological semiclassical Einstein equation (SCE). The SCE describes the interaction of relativistic quantum matter by the expected value of the renormalized stress-energy tensor of a quantum field with classical gravity. Here, we consider a free, massless scalar field with general (not necessarily conformal) coupling to curvature. In a cosmological scenario with flat spatial sections for special choices of the initial conditions, we observe a separation of the dynamics of the quantum degrees of freedom from the dynamics of the scale factor, which extends a classical result by A. A. Starobinsky [Phys. Lett., B 91, No. 1, 99–102 (1980; Zbl 1371.83222)] to general coupling. For this new equation of fourth order governing the dynamics of the scale factor, we study numerical solutions. Typical solutions show a radiation-like Big Bang for the early Universe and de Sitter-like expansion for the late Universe. We discuss a specific solution to the cosmological horizon problem that can be produced by tuning parameters in the given equation. Although the model proposed here only contains massless matter, we give a preliminary comparison of the obtained cosmology with the \(\Lambda\)CDM standard model of cosmology and investigate parameter ranges in which the new models, to a certain extent, is capable of assimilating standard cosmology.

MSC:

83C05 Einstein’s equations (general structure, canonical formalism, Cauchy problems)
81Q20 Semiclassical techniques, including WKB and Maslov methods applied to problems in quantum theory
83F05 Relativistic cosmology
83D05 Relativistic gravitational theories other than Einstein’s, including asymmetric field theories
83C30 Asymptotic procedures (radiation, news functions, \(\mathcal{H} \)-spaces, etc.) in general relativity and gravitational theory
81T20 Quantum field theory on curved space or space-time backgrounds
81T17 Renormalization group methods applied to problems in quantum field theory
70S05 Lagrangian formalism and Hamiltonian formalism in mechanics of particles and systems
53C21 Methods of global Riemannian geometry, including PDE methods; curvature restrictions
58J47 Propagation of singularities; initial value problems on manifolds
65H05 Numerical computation of solutions to single equations
83E05 Geometrodynamics and the holographic principle
83C56 Dark matter and dark energy

Citations:

Zbl 1371.83222

References:

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