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Pedro Tarancón-Álvarez (Institute of Cosmos Sciences - University of Barcelona (ICCUB))10/21/26, 3:00 PM
The hydrodynamics of expanding bubbles is a key ingredient in the prediction of gravitational waves from cosmological first-order phase transitions. It fixes which expansion types are possible, and it provides a proxy for how much energy is available for gravitational wave emission. These predictions normally rely on a conformal equation of state, which need not hold in strongly coupled or...
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Anish Ghoshal (University of Sussex, UK)10/21/26, 3:20 PM
Collisions of ultra-relativistic bubbles during cosmological phase transitions can produce particles much heavier than the transition scale. Previous analyses modelled this process as the off-shell decay of the scalar background. We show that its results parametrically overestimate hard particle production and depend on the gauge choice and the coordinate choice in field space. We propose an...
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Henda Mansour (KIT)10/21/26, 3:40 PM
When reheating is delayed, supercooled first-order phase transitions are often assumed to hand the Universe over to an early era of matter domination. In this talk I ask whether this assumption actually holds, and argue that it generally does not — at least not immediately. Bubble collisions leave behind a highly inhomogeneous scalar field with persistent relativistic gradients, producing an...
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Andrzej Wereszczyński (Jagiellonian University, Kraków, Poland)10/21/26, 4:00 PM
I show that the inclusion of a dimension-six operator in the Higgs potential has a dramatic impact on the stability of oscillons in the SU(2) bosonic sector of the Standard Model, extending their lifetime by orders of magnitude. This happens for the physical value of the ratio between the Higgs and W boson masses, mH /mW = 1.556 and for the dimension-six operator (Φ^†Φ)3 whose coupling...
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Satumaaria Sukuvaara (University of Helsinki)10/22/26, 3:00 PM
While cooling down, the early universe is believed to have undergone symmetry breaking phase transitions. One attractive possibility for extending the Standard Model is that these phase transitions are of the first order, as they might be able to produce observable gravitational waves. We consider a dark matter freeze-out mechanism, filtering, where dark matter particles become massive in a...
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Nadir Ijaz (University of Padova, Italy)10/22/26, 3:20 PM
A rolling axion inflaton can amplify one polarization of a gauge field through its pseudoscalar coupling. The amplified fields source scalar fluctuations and gravitational waves, and their backreaction can substantially change the inflaton’s motion. In this talk, I will present our numerical study of this coupled evolution and discuss when the homogeneous-backreaction approximation remains...
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Carlo Tasillo (IFIC, Valencia University)10/22/26, 3:40 PM
A first-order electroweak phase transition in the CP-conserving type-I two-Higgs-doublet model can source a gravitational wave background in the LISA band. From extensive Monte Carlo scans over the collider-viable parameter space, we find that LISA-detectable signals arise almost exclusively where observable deviations at the HL-LHC are predicted, in particular in the H → ZZ channel for a...
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Oliver Gould (University of Nottingham)10/22/26, 4:00 PM
The critical, universal behaviour of any second-order phase transition gives rise to stochastic anisotropic stresses. These in turn source a stochastic spectrum of gravitational waves. In this talk, I show how to derive the rate of gravitational wave production for second-order phase transitions in the simplest dynamical universality class, Model A, describing a diffusive scalar order...
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Alberto García Martín-Caro (Universidades de Vigo)10/23/26, 12:25 PM
Cosmic strings arise naturally in theories with spontaneously broken symmetries and can carry important information about the dynamics of phase transitions in the early Universe. In this talk I will present a systematic framework for deriving the effective action governing the Goldstone degrees of freedom associated with the breaking of spacetime symmetries by string defects, together with...
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Maximilian Bachmaier (University of the Basque Country)10/23/26, 12:45 PM
The Standard Model of particle physics provides a good approximation at low energy scales. In the early hot universe, however, it is assumed that there was a so-called grand unified theory, which unified the three fundamental forces of particle physics. However, all attempts to unify these three forces lead to a possible overabundance of ’t Hooft–Polyakov magnetic monopoles. But why magnetic...
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