skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Dynamics of cosmological perturbations and reheating in the anamorphic universe

Abstract

We discuss scalar-tensor realizations of the Anamorphic cosmological scenario recently proposed by Ijjas and Steinhardt [1]. Through an analysis of the dynamics of cosmological perturbations we obtain constraints on the parameters of the model. We also study gravitational Parker particle production in the contracting Anamorphic phase and we compute the fraction between the energy density of created particles at the end of the phase and the background energy density. We find that, as in the case of inflation, a new mechanism is required to reheat the universe.

Authors:
; ;  [1];  [2]
  1. Physics Department, McGill University, Montreal, QC, H3A 2T8 (Canada)
  2. Departamento de Ciências Naturais, Universidade Federal do Espírito Santo, Rodovia BR 101 Norte, km. 60, São Mateus, ES (Brazil)
Publication Date:
OSTI Identifier:
22679941
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2017; Journal Issue: 04; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMOLOGICAL MODELS; DISTURBANCES; ENERGY DENSITY; PARTICLE PRODUCTION; PERTURBATION THEORY; UNIVERSE

Citation Formats

Graef, L.L., Ferreira, Elisa G.M., Brandenberger, Robert, and Hipólito-Ricaldi, W.S., E-mail: leilagraef@on.br, E-mail: wiliam.ricaldi@ufes.br, E-mail: elisa.ferreira@mail.mcgill.ca, E-mail: rhb@physics.mcgill.ca. Dynamics of cosmological perturbations and reheating in the anamorphic universe. United States: N. p., 2017. Web. doi:10.1088/1475-7516/2017/04/004.
Graef, L.L., Ferreira, Elisa G.M., Brandenberger, Robert, & Hipólito-Ricaldi, W.S., E-mail: leilagraef@on.br, E-mail: wiliam.ricaldi@ufes.br, E-mail: elisa.ferreira@mail.mcgill.ca, E-mail: rhb@physics.mcgill.ca. Dynamics of cosmological perturbations and reheating in the anamorphic universe. United States. doi:10.1088/1475-7516/2017/04/004.
Graef, L.L., Ferreira, Elisa G.M., Brandenberger, Robert, and Hipólito-Ricaldi, W.S., E-mail: leilagraef@on.br, E-mail: wiliam.ricaldi@ufes.br, E-mail: elisa.ferreira@mail.mcgill.ca, E-mail: rhb@physics.mcgill.ca. Sat . "Dynamics of cosmological perturbations and reheating in the anamorphic universe". United States. doi:10.1088/1475-7516/2017/04/004.
@article{osti_22679941,
title = {Dynamics of cosmological perturbations and reheating in the anamorphic universe},
author = {Graef, L.L. and Ferreira, Elisa G.M. and Brandenberger, Robert and Hipólito-Ricaldi, W.S., E-mail: leilagraef@on.br, E-mail: wiliam.ricaldi@ufes.br, E-mail: elisa.ferreira@mail.mcgill.ca, E-mail: rhb@physics.mcgill.ca},
abstractNote = {We discuss scalar-tensor realizations of the Anamorphic cosmological scenario recently proposed by Ijjas and Steinhardt [1]. Through an analysis of the dynamics of cosmological perturbations we obtain constraints on the parameters of the model. We also study gravitational Parker particle production in the contracting Anamorphic phase and we compute the fraction between the energy density of created particles at the end of the phase and the background energy density. We find that, as in the case of inflation, a new mechanism is required to reheat the universe.},
doi = {10.1088/1475-7516/2017/04/004},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 04,
volume = 2017,
place = {United States},
year = {Sat Apr 01 00:00:00 EDT 2017},
month = {Sat Apr 01 00:00:00 EDT 2017}
}
  • The emergence of the cosmological composition (the reheating era) after the inflationary period is analyzed in the framework of the braneworld models, in which our Universe is a 3-brane embedded in a five-dimensional bulk, by assuming the possibility of brane-bulk energy exchange. The inflaton field is assumed to decay into normal matter only, while the dark matter is injected into the brane from the bulk. To describe the reheating process we adopt a phenomenological approach, by describing the decay of the inflaton field using a friction term proportional to the energy density of the field. After the radiation dominated epochmore » the model reduces to the standard four-dimensional cosmological model. The modified field equations are analyzed analytically and numerically in both the extra-dimension dominated reheating phase (when the quadratic terms in energy density dominate the dynamics) and the general case. The evolution profiles of the matter, of the scalar field and of the scale factor of the Universe are obtained for different values of the parameters of the model and of the equations of state of the normal and dark matter. The equation describing the time evolution of the ratio of the energy densities of the dark and the normal matter is also obtained. The ratio depends on the rate of energy flow between the bulk and the brane. The observational constraint of an approximately constant ratio of the dark and the baryonic matter requires that the dark matter must be non-relativistic (cold). The model predicts a reheating temperature of the order of 3 Multiplication-Sign 10{sup 6} GeV, a brane tension of the order of 10{sup 25} GeV{sup 4}, and the composition of the Universe obtained is consistent with the observational data.« less
  • We study the growth of energy-density perturbations in inflationary-universe models, applying an extension of Bardeen's gauge-invariant framework derived in a previous paper. The complete analysis is exemplified in the case of the ''new inflationary universe'' of Linde and Albrecht and Steinhardt. For this model we obtain the following result: the amplitude of energy-density fluctuations at horizon crossing is of order 50, far too large to match with the usual pictures of galaxy formation. Our result agrees with other published analyses. We conclude that the amplification of energy-density perturbations is determined by the change in the equation of state between initialmore » and final Hubble radius crossing. It is, however, independent of the phase structure between the two crossings. In particular, it is independent of the reheating mechanism. We also derive a simple formula which describes the complete evolution of perturbations outside the horizon whenever entropy and anisotropic stress perturbations are unimportant. Finally, we comment on previous published methods and discuss their limitations.« less
  • We elucidate and somewhat extend Bardeen's gauge-invariant formalism for calculating the growth of linear gravitational perturbations in a Friedmann-Robertson-Walker cosmological background. We show that the formalism can be derived from the usual gravitational Lagrangian, by variation with respect to a restricted set of metric perturbation functions. This approach produces a natural decomposition of an arbitrary matter field (whose constitutive equations need not resemble the usual cosmological perfect fluid) into a spatially homogeneous piece, which couples to the background metric, plus a spatially inhomogeneous piece, which is not necessarily small and which is the source term in a second-order differential equationmore » which evolves the gauge-invariant metric perturbation potential. We show how the complete perturbed metric can be reconstructed in arbitrary gauge from the single gauge-independent metric potential, so that the evolution of the matter fields can be concurrently calculated in the usual manner (i.e., in a perturbed coordinate frame). The approach of this paper is designed to be particularly suited to the study of fluctuations generated by classical scalar or gauge fields in ''inflationary'' cosmological models.« less
  • Energy-density perturbations in a universe dominated by coherent oscillations of a scalar field evolve as in a pressureless fluid. The analysis applies in particular to axion models. Axions are thus a candidate for cold dark matter.
  • We discuss second-order cosmological perturbations on super-Hubble scales, in a scalar field dominated universe, such as during single field inflation. In this contest we show that the gauge-invariant curvature perturbations defined on uniform density and comoving hypersurfaces coincide and that perturbations are adiabatic in the large scale limit. Since it has been recently shown that the uniform density curvature perturbation is conserved on large scales if perturbations are adiabatic, we conclude that both the uniform density and comoving curvature perturbations at second order, in a scalar field dominated universe, are conserved. Finally, in the light of this result, we commentmore » on the variables recently used in the literature to compute non-Gaussianities.« less