Cosmological phase transitions (PTs) are fascinating events taking place in the first instants of our Universe. First order PTs proceeding via the nucleation and expansion of bubbles are of particular interest as they can impart a strong departure from thermal equilibrium, with important implications for the matter-antimatter asymmetry as well as the copious production of primordial...
We study the possibility that axion strings in the DFSZ model can act as seeds for the electroweak(EW) first-order phase transition. Unlike the KSVZ case, the DFSZ axion strings can couple to the Higgs sector via a "axion-dependent" portal interaction. We analyze the resulting effective theory and find that string-induced EW bubbles have a different feature from usual bubbles or string-seeded...
A cosmological inverse first-order phase transition is an endothermic event in which bubbles of the new phase expand by absorbing latent heat and pulling the surrounding plasma inward—opposite to the usual (exothermic) outward flow. Such behaviour was thought possible only during a reheating phase, when the cosmic temperature rises. We show it can emerge naturally while the Universe cools. In...
Inverse phase transitions in which tunneling proceeds into a finite-temperature vacuum away from the zero-temperature vacuum exhibit different fluid profiles than usual (direct) transitions. We investigate the effect this has on the sound wave contribution to the stochastic gravitational wave background generated in such transitions.
We study friction effects on the expanding bubble wall in first order phase transitions (FOPT) with symmetry restoration, where particles become massless inside the bubble. We consider leading order (LO) and next-to leading order (NLO) friction effects of the surrounding plasma.
The inverse case, with symmetry breaking, is well studied and shows that LO friction effects decrease the bubble...
Strong first-order phase transitions offer a compelling explanation for the stochastic gravitational wave background in the nano-Hertz range measured by pulsar timing arrays (PTA). In this talk, I will consider a classically conformal dark sector in which the breaking of a dark U(1) gauge symmetry gives rise to a gravitational wave background that can fit the PTA data and additionally sources...
We explore the dynamics of cosmological phase transitions in a dark sector model featuring a dark photon associated with a U(1)D gauge symmetry and radiative symmetry breaking. Our analysis focuses on different approaches to construct the effective potential: the high-temperature approximation, a full numerical evaluation of the thermal integrals, and a dimensionally reduced 3D effective...
Cosmological phase transitions can give rise to intriguing phenomena, such as baryogenesis or a stochastic gravitational wave background, due to nucleation and percolation of vacuum bubbles in the primordial plasma. A key parameter for predicting these relics is the bubble wall velocity, whose computation relies onsolving the Boltzmann equations of the various speciesalong the bubble profile....
First-order phase transitions (FOPT) in the early universe are a unique probe of physics beyond the Standard Model, playing a key role in electroweak baryogenesis and many different phenomena. Future gravitational wave detectors will allow us to see the signature of possible FOPT, but to extract theoretical value from it, we need a precise understanding of their dynamics. In this talk, I...
