The JWST and standard cosmology

Abstract

Recent observations from the James Webb Space Telescope have identified a population of massive galaxy sources ($\mathrm{>10^{10}\ M_\odot}$) at $z>7-10$, formed less than 700 Myr after the Big Bang. Such massive galaxies do not have enough time to form within the standard cosmological model, and hence these observations significantly challenge standard cosmology. A number of possible solutions to this problem have been put forward, including an enhancement of the gravitational force in a modified theory of gravity and the claim that massive primordial black holes, which were created in the early universe before galaxy formation, might provide seeds for galaxies and black holes to subsequently form. We discuss two more exotic possibilities. Black holes can persist through a cosmological bounce and constitute large seeds formed in the previous cosmic cycle existing before current galaxy formation. And spikes, both incomplete spikes that occur in the early initial oscillatory regime of general cosmological models and permanent spikes that can form in inhomogeneous models at later times, could provide a mechanism for generating large structures early in the Universe.