Blast-frozen Dark Matter and Modulated Density Perturbations

First-order phase transitions (FOPT) are ubiquitous in beyond the Standard Model physics and leave distinctive echoes in the history of early universe. We consider a FOPT serving the well-motivated role of dark matter mass generation and present {\it blast-frozen dark matter} (BFDM), which transitions from radiation to non-relativistic relic in a period much shorter than the corresponding Hubble time. Its cosmological imprint are strong oscillations in the dark matter density perturbations that seed structure formation on large and small scales. For a FOPT occurring not long before the matter-radiation equality, next generation cosmological surveys bear a strong potential to discover BFDM and in turn establish the origin of dark matter mass.

💡 Research Summary

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The paper introduces a novel dark‑matter (DM) scenario called “blast‑frozen dark matter” (BFDM), in which the DM mass is generated by a first‑order phase transition (FOPT) that proceeds extremely rapidly—much faster than a Hubble time. Prior to the transition the DM is essentially massless and behaves as a relativistic fluid with equation‑of‑state w≈1/3; after the transition it becomes non‑relativistic with w≈0. The rapidity of the transition is quantified by the inverse duration β, and the authors focus on the limit β/H_≫1 (β/H_ is the ratio of the transition rate to the Hubble rate at the nucleation temperature T_*). In this limit the fraction of space still in the false vacuum drops as F(t)≈exp