Primordial black holes in an accelerating universe

General expressions are given for the generation of Primordial Black Holes (PBH) in a universe with a presently accelerated expansion due to an (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 A and assuming flatness, we show that a cosmological 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. (C) 2002 Elsevier Science B.V All rights reserved.