We describe a new scenario for the formation of primordial black holes (PBHs). In the early Universe, the long-range forces mediated by the scalar fields can lead to formation of halos of heavy ...particles even during the radiation-dominated era. The same interactions result in the emission of scalar radiation from the motion and close encounters of particles in such halos. Radiative cooling due the scalar radiation allows the halos to collapse to black holes. We illustrate this scenario on a simple model with fermions interacting via the Yukawa forces. The abundance and the mass function of PBHs are suitable to account for all dark matter, or for some gravitational wave events detected by LIGO. The model relates the mass of the dark-sector particles to the masses and abundance of dark matter PBHs in a way that can explain why the dark matter and the ordinary matter have similar mass densities. The model also predicts a small contribution to the number of effective light degrees of freedom, which can help reconcile different measurements of the Hubble constant.
Primordial black holes (PBHs) could account for all or part of dark matter, as well as for some LIGO events. We discuss the spins of primordial black holes produced in different cosmological ...scenarios, with the emphasis on recently discovered possibilities. PBHs produced as a horizon-size collapse of density perturbations are known to have very small spins. In contrast, PBHs resulting from assembly of matterlike objects (particles, Q-balls, oscillons, etc.) can have large or small spins depending on their formation history and the efficiency of radiative cooling. We show that scalar radiation can remove the angular momentum very efficiently, leading to slowly rotating PBHs in those scenarios for which the radiative cooling is important. Gravitational waves astronomy offers an opportunity to determine the spins of black holes, opening a new window on the early Universe if, indeed, some black holes have primordial origin.
The COVID-19 pandemic has forced the health public authorities to impose a lockdown as an epidemiological containment strategy. This study aimed to provide information regarding the impact of the ...mandatory confinement on the physical activity, eating disorders risk, sleep quality and well-being on a Spanish sample. An online survey that included the Minnesota Leisure Time Physical Activity Questionnaire, the Eating Attitude Test-26, and Pittsburgh Sleep Quality Index was administered two days after the state of alarm was stablished in Spain and five days after such measures began to be eased. Out of the 693 people who answered the first questionnaire, 161 completed the second one. These participants spent a total of 48 days locked at home, a period during which a significant worsening in all the variables assessed except for the risk of developing eating disorders, was observed: weight (kg), 67.3 ± 14.8 vs 67.7 ± 15.1, p = 0.012; physical activity (MET minutes per week), 8515.7 ± 10260.0 vs 5053.5 ± 5502.0, p < 0.001; sleep problems (total score), 6.2 ± 3.5 vs 7.2 ± 3.9, p < 0.001; self-perceived well-being (score), 4 (3–4) vs 3 (3–4), p < 0.001. The confinement had a significant differential effect on physically active participants, who experienced a significant decline (p < 0.05) on their physical activity levels, quality of sleep and well-being; whereas physically inactive participants did not experience significant changes. Findings from this longitudinal study indicate that a lockdown period due to COVID-19 had a negative impact on the physical activity levels, sleep quality and well-being in a group of physically active Spanish adults. Public health authorities should be aware that people who usually lead an active lifestyle, might be particularly susceptible to such disruptions.
Abstract
We show that supersymmetry and inflation, in a broad class of models, generically lead to formation of primordial black holes (PBHs) that can account for dark matter. Supersymmetry predicts ...a number of scalar fields that develop a coherent condensate along the flat directions of the potential at the end of inflation. The subsequent evolution of the condensate involves perturbative decay, as well as fragmentation into Q-balls, which can interact by some long-range forces mediated by the scalar fields. The attractive scalar long-range interactions between Q-balls facilitates the growth of Q-balls until their ultimate collapse to black holes. For a flat direction lifted by supersymmetry breaking at the scale Λ ∼ 100 TeV, the black hole masses are of the order of (
M
3
Planck
/Λ
2
) ∼ 10
22
g, in the allowed range for dark matter. Similar potentials with a lower scale Λ (not necessarily associated with supersymmetry) can result in a population of primordial black holes with larger masses, which can explain some recently reported microlensing events.
We reexamine production of primordial black holes in a supercooled phase transition. While a mere overdensity associated with a surviving false-vacuum patch does not imply formation of a black hole, ...it is possible for such a patch to evolve and create a black hole, thanks to the gradient energy stored in the bubble wall. Published by the American Physical Society 2024
The existence of scalar fields can be probed by observations of stochastic gravitational waves. Scalar fields mediate attractive forces, usually stronger than gravity, on the length scales shorter ...than their Compton wavelengths, which can be non-negligible in the early Universe, when the horizon size is small. These attractive forces exhibit an instability similar to the gravitational instability, only stronger. They can, therefore, lead to the growth of structures in some species. We identify a gravitational waves signature of such processes and show that it can be detected by future gravitational waves experiments.
Defrosting and Blast Freezing Dark Matter Flores, Marcos M.; Kouvaris, Chris; Kusenko, Alexander
Physical review. D,
11/2023, Letnik:
108, Številka:
10
Journal Article
Recenzirano
Odprti dostop
We show that the present-day dark matter abundance can be produced through a novel mechanism that involves a very rapid thermal freeze-out caused by inhomogeneous heating and successive fast cooling ...of small fireballs in the early Universe. The fireballs can be produced from energy deposited in small scale structure growth induced by Yukawa interactions in certain particle species. Yukawa interactions are known to cause growth of halos even during a radiation dominated era, and the same interactions facilitate cooling and collapse of the halos by the emission of scalars. Energy deposited in the Standard Model plasma at the locations of the halo collapse can heat the plasma, re-establishing thermal equilibrium. The subsequent expansion and cooling of plasma fireballs leads to freeze-out of dark matter on timescales much shorter than the Hubble time. This mechanism can produce the right abundance of dark matter for masses and annihilation cross sections previously thought to be ruled out.
G objects and primordial black holes Flores, Marcos M.; Kusenko, Alexander; Ghez, Andrea M. ...
Physical review. D,
09/2023, Letnik:
108, Številka:
6
Journal Article
Recenzirano
We suggest that "G objects" recently discovered in the Galactic Center may be clouds of gas bound by the gravitational field of stellar-mass black holes produced in the interactions of sublunar ...primordial black holes with neutron stars. If dark matter is composed of primordial black holes with masses (10–16–10–10)M⊙, these black holes can be captured by neutron stars in the Galactic Center, where the dark matter density is high. After the capture, the neutron star is consumed by the black hole, resulting in a population of (1–2)M⊙ black holes. Furthermore, these stellar-mass black holes, accompanied by gaseous atmospheres, can account for the observed properties of the G objects, including their resilience to tidal disruption by the supermassive black hole in the Galactic Center while also producing emission consistent with inferred luminosities.
We investigate the generation of the baryon asymmetry within the framework of cosmological gravitational particle production, employing the Bogoliubov approach. We examine two well-known baryogenesis ...scenarios, namely baryogenesis in grand unified theories (GUT) and leptogenesis, while considering reheating temperatures sufficiently low for thermal processes to be negligible. Considering α –attractor T-models for the inflaton potential, we demonstrate that GUT baryogenesis from scalar decays can be successful across a large range of conformal couplings with gravity, without necessitating substantial levels of C P violation. In the case of leptogenesis, we find that the reheating temperature should be T RH ≲ 10 6 GeV for right-handed neutrino masses M 1 ≲ 6 × 10 12 GeV to generate the observed asymmetry. Published by the American Physical Society 2024
Luminescent copper(I)‐based compounds have recently attracted much attention since they can reach very high emission quantum yields. Interestingly, Cu(I) clusters can also be emissive, and the ...extension from small molecules to larger architecture could represent the first step towards novel materials that could be obtained by programming the units to undergo self‐assembly. However, for Cu(I) compounds the formation of supramolecular systems is challenging due to the coordinative diversity of copper centers. This works shows that this diversity can be exploited in the construction of responsive systems. In detail, the changes in the emissive profile of different aggregates formed in water by phosphine‐thioether copper(I) derivatives were followed. Our results demonstrate that the self‐assembly and disassembly of Cu(I)‐based coordination polymeric nanoparticles (CPNs) is sensitive to solvent composition. The solvent‐induced changes are related to modifications in the coordination sphere of copper at the molecular level, which alters not only the emission profile but also the morphology of the aggregates. Our findings are expected to inspire the construction of smart supramolecular systems based on dynamic coordinative metal centers.
Stable copper(I) coordination polymer nanoparticles (CPNs) are self‐assembled in water and they display solvent composition‐responsive behavior that can be followed by emission of the aggregates. The dramatic differences in the emission energy and the morphology of the aggregates have been attributed to changes in the coordination sphere around the copper centers.
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