2025/06/05 by Annala, Jaakko, Rummukainen, Kari, Tenkanen, Tuomas V. I.
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #High Energy Physics - Lattice (hep-lat) #High Energy Physics - Phenomenology (hep-ph)
paper · doi:10.48550/arxiv.2506.04939
In many extensions of the Standard Model electroweak phase transitions at high temperatures can be described in a minimal dimensionally reduced effective theory with SU(2) gauge field and fundamental Higgs scalar. In this effective theory, all thermodynamic information is governed by two dimensionless ratios x ≡ λ3/g23 and y≡ m23/g43, where λ3, m23 and g3 are the effective thermal scalar self-interaction coupling, the thermal mass and the effective gauge-coupling, respectively. By using non-perturbative lattice simulations to determine the rate of sphaleron transitions in the entire (x,y)-plane corresponding to the Higgs phase, and by applying previous lattice results for the bubble nucleation, we find a condition x(Tc) \lesssim 0.025 to guarantee preservation of the baryon asymmetry, which translates to v/Tc ≡ √(2 ⟨ ϕ^† ϕ⟩)/Tc \gtrsim 1.33 for the (gauge-invariant) Higgs condensate. This indicates that viability of the electroweak baryogenesis requires the phase transition to be slightly stronger than previously anticipated. Finally, we present a general template for analysing such viability in a wide class of beyond the Standard Model theories, in which new fields are heavy enough to be integrated out at high temperature.