Centro de Excelencia Severo Ochoa
Menú
Buscar
Primordial black holes from inflation and their gravitational wave signals
Specialist level
Speaker:
Julián Rey
Location&Place:
Blue Room
Abstract:
We consider the possibility that the majority of dark matter in the Universe consists of black holes of primordial origin, and study the prospects of generating them in single-field models of inflation. Three different scenarios are presented. The first two rely on the presence of an ultra-slow-roll phase in inflation due to an inflection point in the potential. One of these scenarios is characterized by a quartic polynomial potential and is (arguably) the simplest model of inflation able to produce a large population of primordial black holes. The second scenario is aimed at ameliorating the tuning problems present in inflection-point models, and involves a setup that employs the advantages of gravitational collapse in a long epoch of early matter domination, as well as a potential based on a string-inspired class of models in which the inflaton is identified with a non-compact axion field. The third scenario we consider is fundamentally different from the inflection-point models, and consists on obtaining the large peak in the power spectrum of curvature perturbations necessary for black hole formation from a transient dissipative phase during inflation. In this case the enhancement of the power spectrum occurs due to the presence of a stochastic thermal noise source in the equation of motion for the fluctuations.
We consider the impact of quantum diffusion on the inflationary dynamics during an ultra-slow-roll phase and show, by means of a fully analytical approach, that the power spectrum of comoving curvature perturbations computed in stochastic inflation matches precisely, at the linear level, the result obtained by solving the Mukhanov-Sasaki equation. Finally, we compute the stochastic background of gravitational waves generated in each scenario. In particular, we study the gravitational waves induced during an early matter-dominated era and determine how much of the parameter space remains available after taking into account the bounds on the gravitational wave energy density arising from the abundance of light elements produced during Big-Bang nucleosynthesis and cosmic microwave background experiments. We examine the gauge dependence of the resulting signal and, by using a heuristic argument based on symmetry properties and dimensional analysis, determine the full gaugeinvariant expression for the energy density of gravitational waves at next-to-leading order in perturbations. We discuss the prospects of detecting the resulting signal with the LISA experiment.
pie de foto:
pie de foto:
pie de foto:
Social media