Finite-temperature bubble nucleation with shifting scale hierarchies

by Philipp Schicho (University of Geneva)

Monday 11 May 2026, 14:00 → 16:00 Europe/Rome

Scale hierarchies are required to reliably describe the thermodynamics of cosmological first-order phase transitions using perturbation theory. At finite temperature, such a hierarchy is provided naturally. One can then use this hierarchy to construct a three-dimensional effective field theory (EFT) that systematically includes thermal resummations to all orders.

 

Using this EFT framework, I focus on supercooled phase transitions in models with classical scale symmetry [1,2]. By computing the bubble nucleation rate and accounting for the presence of varying energy scales, I examine the limitations of derivative expansions in constructing a thermal effective field theory for bubble nucleation. In particular, for gauge-field fluctuations, the derivative expansion breaks down beyond the first two terms due to strong variations in gauge-field masses between the high- and low-temperature phases.

 

By directly computing these contributions using the fluctuation determinant, I demonstrate how this approach significantly improves nucleation rate calculations compared to leading-order results, providing a more robust framework for predicting gravitational-wave signals from supercooled phase transitions.

 

[1] M. Kierkla, P. Schicho, B. Swiezewska, T. V. I. Tenkanen, and J. van de Vis, Finite-
temperature bubble nucleation with shifting scale hierarchies, JHEP 07, 153 (2025),
[2503.13597].
[2] M. Kierkla, N. Ramberg, P. Schicho, and D. Schmitt, Theoretical uncertainties for
primordial black holes from cosmological phase transitions, (2025), [2506.15496].