2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/187073Non-perturbative effects in the high-temperature phase of the electroweak theory are characterized by a magnetic screening length. Its size influences the range of validity of perturbation theory, and it also determines the critical Higgs boson mass where the first-order phase transition changes to a crossover. We propose a gauge-invariant definition of the magnetic screening length and discuss its role in several gauge-dependent and gauge-invariant correlation functions.11 pages Latex, 3 figures, uses epsf.styHigh Energy Physics - Phenomenologytext