If Primordial Black-Holes Exist, What Would Be The Gravitational Wave Background Noise They Would Produce For LISA, DECIGO, And BBO?

Abstract

According to the standard model primordial black holes (PBHs) could have been generated during the first few moments after the big bang as consequence of density fluctuations of matter. Although most regions of high density would be quickly dispersed by the expansion of the universe, primordial black holes would be stable, persisting to the present. If this really happened some of the space detectors as the Laser Interferometer Space Antenna (LISA), the DECihertz Interferometer Gravitational wave Observatory (DECIGO), and the Big Bang Observer (BBO) will probably detect the gravitational wave background produced by those PBHs. Here we calculated this background as a function of the signal frequency and the PBH merger rate in our Milky Way galaxy. Even for the highest estimated rate of PBH mergers in our Milky Way halo (∼ 1.2 × 10−2 yr−1 MWH−1), in which all MACHOs would be PBHs, we don’t expect that PBH binaries will produce a confusion noise too much above the low end of the LISA sensitivity band for frequencies below 10−3 Hz. Furthermore, very large ground base interferometers such as LIGO and VIRGO can soon put constraints on this rate. Finally, we can say that in any case DECIGO and BBO are free from facing a PBH confusion noise.