Black Holes and Neutron Stars in an Oscillating Universe

In recent years, hypotheses about a cyclical Universe have been again actively considered. In these cosmological theories, the Universe, instead of a "one-time" infinite expansion, periodically shrinks to a certain volume, and then again experiences the Big Bang. One of the problems for the cyclic Universe will be its compatibility with a vast population of indestructible black holes that accumulate from cycle to cycle. The article considers a simple iterative model of the evolution of black holes in a cyclic Universe, independent of specific cosmological theories. The model has two free parameters that determine the iterative decrease in the number of black holes and the increase in their individual mass. It is shown that this model, with wide variations in the parameters, explains the observed number of supermassive black holes at the centers of galaxies, as well as the relationships between different classes of black holes. The mechanism of accumulation of relict black holes during repeated pulsations of the Universe may be responsible for the black hole population detected by LIGO observations and probably responsible for the dark matter phenomenon. The number of black holes of intermediate masses corresponds to the number of globular clusters and dwarf satellite galaxies. These results argue for models of the oscillating Universe, and at the same time impose substantial requirements on them. Models of a pulsating Universe should be characterized by a high level of relict gravitational radiation generated at the time of maximum compression of the Universe and mass mergers of black holes, as well as solve the problem of the existence of the largest black hole that is formed during this merger. It has been hypothesized that some neutron stars can survive from past cycles of the Universe and contribute to dark matter. These relict neutron stars will have a set of features by which they can be distinguished from neutron stars born in the current cycle of the birth of the Universe. The observational signs of relict neutron stars and the possibility of their search in different wavelength ranges are discussed.