Albert Escrivà

In this paper, we argue and show numerically that the threshold to form primordial black holes from an initial spherically symmetric perturbation is, to an excellent approximation, universal, whenever given in terms of the compaction function averaged over a sphere of radius ${r}_{m}$, where ${r}_{m}$ is the scale on which the compaction function is maximum. This can be understood as the requirement that, for a black hole to form, each shell of the averaged compaction function should have an amp

We consider black holes which form from an initially spherically symmetric super-Hubble perturbation of a cosmological background filled by a perfect fluid $p=w \rho$ with $w\in (0,1]$. Previous work has shown that when $w = 1/3$ (radiation), there is a critical threshold for black hole formation ($\delta_c$), which, to a very good approximation, only depends upon the curvature of the compaction function around its peak value. We find that this generalizes to all $w\gtrsim 1/3$; for smaller $w$s

Primordial black holes, which could have been formed in the very early Universe due to the collapse of large curvature fluctuations, are currently one of the most attractive and fascinating research areas in cosmology for their possible theoretical and observational implications. This review article presents the current results and developments on the conditions for primordial black hole formation from the collapse of curvature fluctuations in spherical symmetry on a Friedman–Lemaître–Robertson–

In this work, we have performed numerical simulations of primordial black hole (PBH) formation in the Friedman-Lema\^itre-Robertson-Walker universe filled by radiation fluid, introducing the local-type non-Gaussianity to the primordial curvature fluctuation. We have compared the numerical results from simulations with previous analytical estimations on the threshold value for PBH formation done in the previous paper arXiv:2109.00791, particularly for negative values of the non-linearity paramete

Abstract The probability of primordial black hole (PBH) formation is known to be boosted during the Quantum Chromodynamics (QCD) crossover due to a slight reduction of the equation of state. This induces a high peak and other features in the PBH mass distribution. But the impact of this variation during the process of PBH formation has so far not been considered in numerical simulations. In this work we simulate the formation of PBHs by taking into account the varying equation of state at the QC

Abstract We simulate numerically the formation of spherically symmetric primordial black holes (PBHs) seeded by different families of primordial curvature perturbations profiles in a radiation dominated Friedman-Robertson-Walker (FRW) Universe. We have studied the dependency on the curvature profile of the initial mass M BH,i of the PBHs at the time of apparent horizon formation t AH , and the final mass M BH,f after the accretion process, using an excision technique, comparing M BH,i to previou

Naive dimensional analysis seems to suggest possible unitarity violations in the framework of the Higgs and new Higgs inflationary scenarios. These violations seem to happen around the value in which the potential energy, per a given Higgs boson's vacuum expectation value, crosses the perturbative cutoff scale calculated around the electroweak vacuum. Conversely to these expectations, we show that, by using an exact analysis of the background dependent cutoff scale, and by including the contribu

Aspects of primordial black holes, i.e. black holes formed in the early Universe, are reviewed. Special emphasis is put on their formation, their role as dark matter candidates and their manifold signatures, particularly through gravitational waves.

Abstract A class of inflationary scenarios for primordial black hole (PBH) formation include a small barrier in the slope of the potential. There, the inflaton slows down, generating an enhancement of primordial perturbations. Moreover, the background solution overcomes the barrier at a very low speed, and large backward quantum fluctuations can prevent certain regions from overshooting the barrier. This leads to localized bubbles where the field remains “trapped” behind the barrier. In such mod

Abstract We consider the formation of primordial black holes (PBHs), during the radiation-dominated Universe, generated from the collapse of super-horizon curvature fluctuations that are overlapped with others on larger scales. Using a set of different curvature profiles, we show that the threshold for PBH formation (defined as the critical peak of the compaction function) can be decreased by several percentages, thanks to the overlapping between two peaks in the profile of the compaction functi

The final mass distribution of primordial black holes is sensitive to the equation of state of the Universe at the scales accessible by the power spectrum. Motivated by the presence of phase transitions in several beyond the Standard Model theories, some of which are strongly coupled, we analyze the production of primordial black holes during such phase transitions, which we model using the gauge/gravity duality. We focus in the (often regarded as physically uninteresting) case for which the pha

The quantum dynamics of population-balanced fractional vortices and population-imbalanced vortices in an effective two-state bosonic system, made of two coupled discrete circuits with few sites, is addressed within the Bose-Hubbard model. We show that, for low on-site interaction, the tunneling of quantized vortices between the rings performs a coherent, oscillating dynamics connecting current states with chiral symmetry. The vortex-flux transfer dually follows the usual sinusoidal particle curr

Gravitational waves (GWs) induced by primordial fluctuations can be affected by the modification of the sound speed ${c}_{\mathrm{s}}^{2}$ and the equation of state parameter $w$ once the curvature fluctuations reenter the cosmological horizon. That softening can also significantly boost the production of primordial black holes (PBHs) at the mass scale where the softening arises. In this work, we consider a hypothetical softening of $w$ and ${c}_{\mathrm{s}}^{2}$ caused by a smooth crossover bey