Upper limits on the size of a primordial black hole

Tomohiro Harada and B. J. Carr
Phys. Rev. D 71, 104009 – Published 10 May 2005

Abstract

We provide precise constraints on the size of any black holes forming in the early Universe for a variety of formation scenarios. In particular, we prove that the size of the apparent horizon of a primordial black hole formed by causal processes in a flat Friedmann universe is considerably smaller than the cosmological apparent horizon size for an equation of state p=kρ (1/3<k<1). This also applies for a stiff equation of state (k=1) or for a massless scalar field. The apparent horizon of a primordial black hole formed through hydrodynamical processes is also considerably smaller than the cosmological apparent horizon for 0<k1. We derive an expression for the maximum size which an overdense region can have without being a separate closed universe rather than part of our own. Newtonian argument shows that a black hole smaller than the cosmological horizon can never accrete much.

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  • Received 6 December 2004

DOI:https://doi.org/10.1103/PhysRevD.71.104009

©2005 American Physical Society

Authors & Affiliations

Tomohiro Harada* and B. J. Carr

  • Astronomy Unit, School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, United Kingdom

  • *Electronic address: T.Harada@qmul.ac.uk
  • Electronic address: B.J.Carr@qmul.ac.uk

See Also

Growth of primordial black holes in a universe containing a massless scalar field

Tomohiro Harada and B. J. Carr
Phys. Rev. D 71, 104010 (2005)

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Vol. 71, Iss. 10 — 15 May 2005

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