Primordial Black Hole cluster dynamics and early Universe models

In this thesis we have studied a particular inflationary model of the early-Universe dynamics, the Higgs-Dilaton Model, a viable extension of the Standard Model of particle physics, and one that is based only on Scale Invariance and a non-minimal coupling to Unimodular Gravity, an extension of General Relativity. The model is able to produce an early-Universe period of inflation necessary to explain the high degree of homogeneity in the cosmic microwave background of temperature anisotropies as well as explaining the present era of accelerated expansion commonly attributed to Dark Energy.

We have studied as well in this thesis the late-Universe dynamics of clusters of Primordial Black Holes, which may emerge indeed as a result of some models of inflation where the curvature perturbation grows above a threshold sufficiently high to produce large enough overdensities in the radiation era that may collapse and coalesce into black holes. These black holes do not arise from astrophysical processes such as the death of stars and are thus commonly referred as Primordial Black Holes. They may constitute latter on the seeds galaxies, accelerate cosmological structure formation, solve a number of open questions in cosmology and last they may explain the nature of Dark Matter as they may constitute an ideal candidate for it.

We have in this manner linked the early Universe dynamics to that of the late Universe in a way that connects the inflationary era to both the present era of accelerated expansion of the Universe commonly attributed to Dark Energy, and to the presently observed abundance of Dark Matter seen in a myriad of cosmological probes from Large Scale Structure surveys to the relic radiation of the Cosmic microwave Background. Note as well that the answers to these problems –both the Dark Matter and the Dark Energy problems– are, notably, longstanding questions in the field of cosmology whose explanation has eluded researchers for decades, and whose study remains to this day one of the most active fields for research in all of physics.