Difference: FJPPLHighEnergyPhysics (17 vs. 18)

Summary:
Several astrophysical or cosmological observations (evidences for dark matter, baryon asymmetry, inflation...) require an extension of the Standard Model of particle physics (so-called “beyond the standard model” (BSM) physics). The links between cosmology and particle physics heavily rely on the understanding on the history of the universe, which is often based on standard assumptions. For instance: an inflationary epoch produces a quasi-power law spectrum of perturbations (seeds of current structures) and ends in a radiation dominated period, during which conventional electroweak symmetry and QCD breaking happen as crossovers, according to the SM. Dark Matter is usually considered to be a particle relic, once in thermal contact with other SM species, etc. We are exploring possible departures from this simple picture. In the classically conformal extension of the SM, S. Iso, P. Serpico, and K. Shimada found that the chiral condensation in QCD can play an important role in the dynamics of the electroweak symmetry breaking. The phase transition becomes of the first order type and accordingly generates large gravitational waves that can be detected by future gravitational wave detectors [2]. Further consequences of this scenario, such as signatures of a late thermal inflationary phase and implications for dark matter, are being investigated. Always related to gravitational waves, it is well known that the LIGO interferometers have detected their first sources of gravitational waves, from coalescences of binary black holes (BHs). While such binaries have long been considered an attractive candidate, the mechanism to produce them is not established, yet, in particular for such high masses (about 30 times the mass of the sun). It has also been conjectured that such BH may be of primordial origin. Their formation requires a significant departure from the simplest inflationary models, and at the same time it would lead to non-standard cosmological signatures, which can be searched for. In [3], we studied the impact of accretion of primordial stellar mass black holes on CMB anisotropies, finding stringent bounds. We are currently extending this study to massive and supermassive primordial black holes, which requires a careful treatment of the accretion in presence of a “dark matter” halo surrounding the black hole.

French members:
V. Poulin, P. Serpico, J. Lavalle, G. Facchinetti, G. Franco Abellan, R. Murgia

Japanese members:
N. Hiroshima, K. Kohri, S. Iso, T. Sekiguchi, H. Matsui, T. Igata

References:
[1] S. Iso, K. Kohri and K. Shimada, "Dynamical fine-tuning of initial conditions for small field inflation," Phys. Rev. D 93, 084009 (2016) [arXiv:1511.05923]
[2] S. Iso, P. D. Serpico and K. Shimada, "QCD-Electroweak first order phase transition in supercooled universe,'' Phys. Rev. Lett. 119, 141301 (2017) [arXiv:1704.04955]
[3] V. Poulin, P. D. Serpico, F. Calore, S. Clesse and K. Kohri, “CMB bounds on disk-accreting massive primordial black holes,'' Phys. Rev. D 96, 083524 (2017) [arXiv:1707.04206]