Thermal tachyacoustic cosmology

Abhineet Agarwal and Niayesh Afshordi
Phys. Rev. D 90, 043528 – Published 27 August 2014

Abstract

An intriguing possibility that can address pathologies in both early Universe cosmology (i.e. the horizon problem) and quantum gravity (i.e. nonrenormalizability), is that particles at very high energies and/or temperatures could propagate arbitrarily fast. A concrete realization of this possibility for the early Universe is the tachyacoustic (or speedy sound) cosmology, which could also produce a scale-invariant spectrum for scalar cosmological perturbations. Here, we study thermal tachyacoustic cosmology (TTC), i.e. this scenario with thermal initial conditions. We find that a phase transition in the early Universe, around the scale of the grand unified theory (GUT scale; T1015  GeV), during which the speed of sound drops by 25 orders of magnitude within a Hubble time, can fit current CMB observations. We further discuss how production of primordial black holes constrains the cosmological acoustic history, while coupling TTC to Horava-Lifshitz gravity leads to a lower limit on the amplitude of tensor modes (r103), that are detectable by CMBpol (and might have already been seen by the BICEP-Keck Collaboration).

  • Figure
  • Received 3 June 2014

DOI:https://doi.org/10.1103/PhysRevD.90.043528

© 2014 American Physical Society

Authors & Affiliations

Abhineet Agarwal1 and Niayesh Afshordi2,1,*

  • 1Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, N2L 3G1 Canada
  • 2Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Ontario, N2L 2Y5 Canada

  • *nafshordi@pitp.ca

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Vol. 90, Iss. 4 — 15 August 2014

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