Primordial Black Holes in an Accelerating Universe

Abstract

General expressions are given for the generation of Primordial Black Holes (PBH) in a universe with a presently accelerated expansion due to a(n effective) cosmological constant. We give expressions both for a powerlaw scalefree primordial spectrum and for spectra which are not of that type. Specializing to the case of a pure cosmological constant $\Lambda$ and assuming flatness, we show that a comological constant with $\Omega_{\Lambda,0}=0.7$ will decrease the mass variance at the PBH formation time by about 15% compared with a critical density universe.