Inhomogeneous anisotropic cosmology
In homogeneous and isotropic FriedmannRobertsonWalker 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 3manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3manifolds 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 »
 Authors:

^{[1]};
^{[2]}
 New York Univ. (NYU), NY (United States). Center for Cosmology and Particle Physics
 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:
 Grant/Contract Number:
 AC0276SF00515; PHY1214302
 Type:
 Accepted Manuscript
 Journal Name:
 Journal of Cosmology and Astroparticle Physics
 Additional Journal Information:
 Journal Volume: 2016; Journal Issue: 10; Journal ID: ISSN 14757516
 Publisher:
 Institute of Physics (IOP)
 Research Org:
 SLAC National Accelerator Lab., Menlo Park, CA (United States)
 Sponsoring Org:
 USDOE; National Science Foundation (NSF)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTRONOMY AND ASTROPHYSICS
 OSTI Identifier:
 1353055
Kleban, Matthew, and Senatore, Leonardo. Inhomogeneous anisotropic cosmology. United States: N. p.,
Web. doi:10.1088/14757516/2016/10/022.
Kleban, Matthew, & Senatore, Leonardo. Inhomogeneous anisotropic cosmology. United States. doi:10.1088/14757516/2016/10/022.
Kleban, Matthew, and Senatore, Leonardo. 2016.
"Inhomogeneous anisotropic cosmology". United States.
doi:10.1088/14757516/2016/10/022. 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 FriedmannRobertsonWalker 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 3manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3manifolds 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 = {10.1088/14757516/2016/10/022},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 10,
volume = 2016,
place = {United States},
year = {2016},
month = {10}
}