Unrestored Electroweak Symmetry.

Area of Science:

• Cosmology
• Particle Physics
• High-Energy Physics

Background:

• The standard cosmological model assumes an electroweak phase transition (EWPT) occurred in the early Universe.
• The strength of this EWPT has significant implications for baryogenesis, gravitational waves, and cosmic evolution.
• However, the assumption of symmetry restoration at high temperatures is not universally applicable, with 'inverse symmetry breaking' observed in scalar theories.

Purpose of the Study:

• To investigate novel electroweak symmetry histories beyond the standard assumption.
• To explore the possibility that electroweak symmetry was always broken or only temporarily restored.
• To analyze the cosmological and collider implications of these alternative phase histories.

Main Methods:

• Proposed a simple extension of the Standard Model.
• Investigated the high-temperature behavior of electroweak symmetry breaking within this extended model.
• Utilized theoretical calculations, drawing parallels with established inverse symmetry breaking phenomena in scalar theories.

Main Results:

• Demonstrated that a simple Standard Model extension allows for scenarios where electroweak symmetry was always broken.
• Showed that the Universe might have only temporarily passed through a symmetry-restored phase.
• Identified novel phase histories with significant cosmological and collider consequences.

Conclusions:

• The commonly assumed electroweak phase transition is not the only possibility.
• Alternative electroweak symmetry histories, including always-broken or temporarily restored phases, are viable.
• The proposed model serves as a benchmark for future research into the Universe's early phase at temperatures around a few GeV.