Abstract: We study the impact of large lepton flavor asymmetries on the cosmic QCD transition. Scenarios of unequal lepton flavor asymmetries are observationally almost unconstrained and therefore open up a whole new parameter space for the cosmic QCD transition. We find that for large asymmetries, the formation of a Bose-Einstein condensate of pions can occur and identify the corresponding parameter space. In the vicinity of the QCD transition scale, we express the pressure in terms of a Taylor expansion with respect to the complete set of chemical potentials. The Taylor coefficients rely on input from lattice QCD calculations from the literature. The domain of applicability of this method is discussed.

Abstract: We study the impact of gas accretion on the orbital evolution of black-hole binaries initially at large separation in the band of the planned Laser Interferometer Space Antenna (LISA). We focus on two sources: (i).stellar-origin black-hole binaries.(SOBHBs) that can migrate from the LISA band to the band of ground-based gravitational-wave (GW) observatories within weeks/months; and (ii) intermediate-mass black-hole binaries.(IMBHBs) in the LISA band only. Because of the large number of observable GW cycles, the phase evolution of these systems needs to be modeled to great accuracy to avoid biasing the estimation of the source parameters. Accretion affects the GW phase at negative (-4) post-Newtonian order, being thus dominant for binaries at large separations. Accretion at the Eddington or at super-Eddington rate will leave a detectable imprint on the dynamics of SOBHBs. For super-Eddington rates and a 10 yr mission, a multiwavelength strategy with LISA and a ground-based interferometer can detect about 10 (a few) SOBHB events for which the accretion rate can be measured at 50% (10%) level. In all cases, the sky position can be identified within much less than 0.4 deg(2) uncertainty. Likewise, accretion at greater than or similar to 100% of the Eddington rate can be measured in IMBHBs up to redshift z approximate to 0.1, and the position of these sources can be identified within less than 0.01 deg(2) uncertainty. Altogether, a detection of SOBHBs or IMBHBs would allow for targeted searches of electromagnetic counterparts to black-hole mergers in gas-rich environments with future X-ray detectors (such as Athena) and/or radio observatories (such as SKA).

Abstract: We study the evolution of the energy distribution and equation of state of the Universe from the end of inflation until the onset of either radiation domination (RD) or a transient period of matter domination (MD). We use both analytical techniques and lattice simulations. We consider two-field models where the inflaton (/) has a monomial potential after inflation V((/)) proportional to i(/) – vip (p 4, and of order similar to 50% for p 4. The system goes to MD at late times for p = 2, while it goes to RD for p > 2. In the later case, we can calculate exactly the number of e-folds until RD as a function of g2, and hence predict accurately inflationary observables like the scalar tilt ns and the tensor-to-scalar ratio r. In the scenario (ii), the energy is always transferred completely to X for p > 2, as long as its effective mass m2X = g2((/) – v)2 is not negligible. For p = 2, the final ratio between the energy densities of X and (/) depends strongly on g2. For all p > 2, the system always goes to MD at late times.