arXiv subjects

Henda Mansour

Publications and source records attributed to Henda Mansour.

3 recordsLinked to original sources

arXiv2026

Can the universe be matter-dominated after a supercooled first-order phase transition?

We show that the answer is generally no, at least not immediately. Bubble collisions leave behind a highly inhomogeneous scalar field with persistent relativistic gradients, producing an equation of state between matter and radiation. Using lattice simulations in one, two and three spatial dimensions, we find that the equation of state is controlled by the wall Lorentz factor at collision $γ_\star$: walls with larger $γ_\star$ populate higher-momentum modes and drive the fluid closer to radiation. Matter domination begins only after these modes redshift, at $a/a_\star \simeq γ_\star$, or after the field thermalises through self-scattering and number-changing processes. This delay has direct implications for gravitational waves, primordial black holes and dark matter production.

hep-ph↗

arXiv2025

Dark matter phase-in: producing feebly-interacting particles after a first-order phase transition

The freeze-in mechanism describes the out-of-equilibrium production of dark matter (DM) particles via feeble couplings or non-renormalisable interactions with large suppression scales. In the latter case, predictions suffer from a strong sensitivity to the initial conditions of the universe, such as the details of reheating. In this work, we investigate how this sensitivity is altered in the presence of a cosmological first-order phase transition. We show that freeze-in via non-renormalisable interactions is not always dominated by the highest temperatures of the Standard Model (SM) thermal bath, but instead may be governed by the period immediately after the phase transition, during which the decaying scalar field transfers its energy density to the SM radiation. We refer to this alternative production regime as DM $\textit{phase-in}$. Using numerical and approximate analytical solutions of the relevant Boltzmann equations, we determine the conditions that under which phase-in or conventional freeze-in production dominates the final DM abundance in terms of the type of interaction between the DM and SM particles, the amount of supercooling before and the evolution of the scalar field after the phase transition. In the phase-in regime, the DM abundance is correlated with the peak frequency of the gravitational wave signal associated with the phase transition, opening up new observational possibilities.

hep-ph↗

arXiv2025

On Particle Production from Phase Transition Bubbles

While first order phase transitions (FOPTs) have been extensively studied as promising cosmological sources of gravitational waves, the phenomenon of particle production from the dynamics of the background field during FOPTs has received relatively little attention in the literature, where it has only been studied with semi-analytic estimates in some simplified settings. This paper provides improved numerical studies of this effect in more realistic frameworks, revealing important qualitative details that have been missed in the literature. We also provide easy to use analytic formulae that can be used to calculate particle production in generic FOPT setups.

hep-ph↗