Speaker: Joaquim Iguaz (LAPTh, CNRS)
Are PBHs everything everywhere all at once? Astrophysical and cosmological signatures of PBHs
In recent years, Primordial Black Holes (PBHs) have been presented as extremely versatile objects providing a unique probe of the early Universe, gravitational phenomena, high energy physics and quantum gravity. Of particular interest is the role of PBHs as a non-particle candidate for the dark matter (DM). Although most of the PBH DM parameter space is tightly constrained, the asteroid mass range is still potentially viable. The lower end is accessible via high-energy astrophysical probes, sensitive to their Hawking evaporation spectrum. In the first part of the talk, I will revisit the constraints on evaporating PBHs from both the isotropic X-ray and soft γ-ray background, and the diffuse soft γ-ray emission towards the inner Galaxy as measured by INTEGRAL, setting the strongest limit on PBH DM for masses up to 4×10^17 g. The interest for PBHs has also been revamped in the light of recent LIGO/Virgo measurements of coalescing black hole binaries with typical masses of tens of M⊙. The best-motivated scenario for a sizable PBH contribution to such events invokes the QCD phase transition, which naturally enhances the probability to form PBH with masses of stellar scale. In the second part of the talk, I will reconsider the expected mass function associated not only to the QCD phase transition proper, but also the following particle antiparticle annihilation processes, and analyse the constraints on this scenario from a number of observations. We find that the scenario is not viable, unless ad hoc features in the power-spectrum are introduced by hand. Despite these negative results, we note that a future detection of coalescing binaries involving sub-solar PBHs has the potential to check the cosmological origin of SMBHs at the e± annihilation epoch, if indeed the PBH mass function is shaped by the changes to the equation of state driven by the thermal history of the universe.
Speaker: Christopher Cappiello (Queen's U)
Dark Matter from Monogem
As a supernova shock expands into space, it may collide with dark matter particles, scattering them up to velocities more than an order of magnitude larger than typical dark matter velocities in the Milky Way. If a supernova remnant is close enough to Earth, and the appropriate age, this flux of high-velocity dark matter could be detectable in direct detection experiments, particularly if the dark matter interacts via a velocity-dependent operator. This could make it easier to detect light dark matter that would otherwise have too little energy to be detected. We show that the Monogem Ring supernova remnant is both close enough and the correct age to produce such a flux, and thus we produce novel direct detection constraints and sensitivities for future experiments.