Physicists Propose New Mechanism for Eliminating Cosmic Domain Walls in Beyond-Standard-Model Theories
Researchers have proposed a new mechanism for the annihilation of domain walls—topological defects that form when global symmetries are broken by gravitational effects—in particle physics theories beyond the Standard Model. The mechanism relies on small bare mass terms in fermions coupled to symmetry-breaking scalars, which generate temperature-dependent biases that trigger domain wall annihilation. This addresses a long-standing cosmological problem where domain walls would otherwise accumulate and dominate the universe's energy density.
A new theoretical study published on arXiv proposes a solution to the cosmological domain wall problem that arises in beyond-Standard-Model physics. When global U(1) symmetries are broken by gravitational effects at the Planck scale, they can reduce to discrete subgroups, creating cosmic strings attached to multiple domain walls. These domain walls are problematic because their slow scaling behavior would eventually dominate the universe's energy density, contradicting observations from Big Bang Nucleosynthesis. The researchers propose that small bare mass terms in fermions coupled to the symmetry-breaking scalar can generate temperature-dependent biases that trigger domain wall annihilation. They demonstrate this mechanism using a majoron framework with right-handed neutrinos, showing how the small bare masses provide the necessary bias for network annihilation.
What's missing
The study does not discuss observational tests or experimental signatures that could distinguish this mechanism from alternative solutions to the domain wall problem, nor does it address whether this mechanism applies to other symmetry groups beyond U(1).
What different sources said
- arXiv astro-phCenter
A New Route to the Annihilation of Multi-Wall String Topological Configurations
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