Early-universe CPT violation viability

Determine whether CPT symmetry could have been violated at high temperatures in the early universe while remaining unobservable today, by identifying conditions under which temperature-dependent CPT-violating effects vanish at present-day temperatures yet produce measurable consequences during Big Bang Nucleosynthesis.

Background

CPT symmetry requires particle–antiparticle mass equality and is stringently tested in laboratory conditions today, but those bounds apply at effectively zero temperature. The paper studies scenarios where CPT-violating electron–positron mass asymmetries arise from a temperature-dependent background b0(T)=αT^2, potentially significant at MeV-scale temperatures during Big Bang Nucleosynthesis while diminishing to negligible levels as T→0.

Using a modified BBN code (PRyMordial) with dynamically solved chemical potentials and finite-mass corrections, the authors explore whether such temperature-dependent CPT violation could alter weak interaction rates, neutrino decoupling, and primordial element abundances while evading present-day constraints. The central uncertainty is whether such CPT violation can occur in the early universe without contradicting current observations.