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Title: Inhomogeneous anisotropic cosmology

Abstract

In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here in this paper, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with "flat'' (including toroidal) and "open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are "flat" or "open". Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with "flat'' or "open" topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energymore » or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.« less

Authors:
 [1];  [2]
  1. New York Univ. (NYU), NY (United States). Center for Cosmology and Particle Physics
  2. Stanford Univ., CA (United States). Stanford Inst. for Theoretical Physics and Dept. of Physics; SLAC National Accelerator Lab., Menlo Park, CA (United States). Kavli Inst. for Particle Astrophysics and Cosmology
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States)
Sponsoring Org.:
National Science Foundation (NSF); USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1353055
Alternate Identifier(s):
OSTI ID: 1491173
Grant/Contract Number:  
AC02-76SF00515; PHY-1214302; SC0008078
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Cosmology and Astroparticle Physics
Additional Journal Information:
Journal Volume: 2016; Journal Issue: 10; Journal ID: ISSN 1475-7516
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; gravity; initial conditions and eternal universe; cosmological simulations; inflation

Citation Formats

Kleban, Matthew, and Senatore, Leonardo. Inhomogeneous anisotropic cosmology. United States: N. p., 2016. Web. doi:10.1088/1475-7516/2016/10/022.
Kleban, Matthew, & Senatore, Leonardo. Inhomogeneous anisotropic cosmology. United States. doi:10.1088/1475-7516/2016/10/022.
Kleban, Matthew, and Senatore, Leonardo. Wed . "Inhomogeneous anisotropic cosmology". United States. doi:10.1088/1475-7516/2016/10/022. https://www.osti.gov/servlets/purl/1353055.
@article{osti_1353055,
title = {Inhomogeneous anisotropic cosmology},
author = {Kleban, Matthew and Senatore, Leonardo},
abstractNote = {In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here in this paper, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with "flat'' (including toroidal) and "open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are "flat" or "open". Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with "flat'' or "open" topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.},
doi = {10.1088/1475-7516/2016/10/022},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 10,
volume = 2016,
place = {United States},
year = {2016},
month = {10}
}

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