Strong and Electro-Weak Matter 2026

Session

Early Universe Contributions 3

20 Aug 2026, 11:00

F4050 (4th floor) (University of Helsinki Main Building)

72. Thermal nucleation in perturbation theory

Joonas Hirvonen (University of Nottingham)

20/08/2026, 11:00

Early universe physics, inflation, electroweak phase transitions, and sources for gravitational waves

talk (30min)

Cosmological first-order phase transitions may have generated a gravitational wave background detectable by LISA, offering a unique window into physics beyond the Standard Model. A crucial step in predicting this background is the reliable computation of bubble nucleation rates. This talk begins with an overview of the current state of perturbative calculations based on effective field...

33. Bubble wall velocity from entropy production

Dr Benoit Laurent (Perimeter Institute)

20/08/2026, 11:30

Early universe physics, inflation, electroweak phase transitions, and sources for gravitational waves

talk (30min)

Cosmological first-order phase transitions are of great phenomenological interest: they can generate a detectable stochastic gravitational wave background, source the baryon asymmetry of the Universe, and seed primordial magnetic fields. A key parameter governing all of these phenomena is the bubble wall velocity $v_w$, which controls the efficiency of each process.

Computing $v_w$ from...

73. Bubble nucleation in cosmological phase transitions

Maciej Kierkla (Uppsala University)

20/08/2026, 12:00

Early universe physics, inflation, electroweak phase transitions, and sources for gravitational waves

talk (15min)

I will present an overview of the calculation of the thermal bubble nucleation rate in the context of cosmological phase transitions. Focusing on the case of “SU(2)+Higgs” like theories, I will illustrate the calculation of nucleation rate in the framework of “high-temperature dimensional reduction”. This perturbative approach can be understood as an effective field theory (EFT) at finite...

108. Dissipative nucleation from a Schwinger–Keldysh perspective

Juan Garnica-Aguirre (University of Warsaw)

20/08/2026, 12:15

Early universe physics, inflation, electroweak phase transitions, and sources for gravitational waves

talk (15min)

In this talk, I will discuss how the Schwinger–Keldysh formalism can be used to describe out-of-equilibrium effects in false vacuum decay during cosmological phase transitions. By integrating out a thermal UV sector in a scalar $\lambda \phi^4$ toy model, we derive a coarse-grained effective action for the IR modes, whose dynamics is both dissipative and stochastic. Formulating the evolution...