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Blast-frozen Dark Matter and Modulated Density Perturbations

Miha Nemevšek, Yue Zhang

TL;DR

Blast-frozen dark matter (BFDM) is proposed as DM that gains mass during a first-order phase transition (FOPT) in the dark sector, driving the DM equation of state from $w=1/3$ to $w\simeq 0$ over a timescale much shorter than the Hubble time. In the limit $\beta/H_* \gg 1$ the transition is effectively instantaneous, enabling analytic solutions for density perturbations in the conformal Newtonian gauge and predicting oscillatory modulations in the matter power spectrum $P(k)$ with a characteristic phase $x_* = k\tau_*/\sqrt{3}$ and amplitude enhancement roughly $\sim x_*^2 \cos x_*$. The model introduces a blast-frozen fraction $f_{\rm BF}$ of DM and a nucleation temperature $T_*$, and confronts the predicted $P(k)$ with current large-scale structure data (SDSS, BOSS) while forecasting sensitivity of future surveys (Spec-S5, PUMA) to BFDM down to $f_{\rm BF} \sim 10^{-4}$ and $T_*$ up to keV. The work also discusses adiabatic initial conditions across the FOPT and notes complementary gravitational-wave probes of the same transition.

Abstract

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.

Blast-frozen Dark Matter and Modulated Density Perturbations

TL;DR

Blast-frozen dark matter (BFDM) is proposed as DM that gains mass during a first-order phase transition (FOPT) in the dark sector, driving the DM equation of state from to over a timescale much shorter than the Hubble time. In the limit the transition is effectively instantaneous, enabling analytic solutions for density perturbations in the conformal Newtonian gauge and predicting oscillatory modulations in the matter power spectrum with a characteristic phase and amplitude enhancement roughly . The model introduces a blast-frozen fraction of DM and a nucleation temperature , and confronts the predicted with current large-scale structure data (SDSS, BOSS) while forecasting sensitivity of future surveys (Spec-S5, PUMA) to BFDM down to and up to keV. The work also discusses adiabatic initial conditions across the FOPT and notes complementary gravitational-wave probes of the same transition.

Abstract

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.

Paper Structure

This paper contains 3 sections, 27 equations, 3 figures.

Table of Contents

  1. End Matter
  2. I. Volume fraction of the false vacuum
  3. II. Comment on other phase transition scenarios

Figures (3)

  • Figure 1: DM density perturbations evolved to the time of MRE. The $\Lambda$CDM model predicts the smooth black curve, whereas the BFDM features oscillations in momentum space shown by the red and yellow curves, corresponding to $\beta/H_*=10$ and 100, respectively. We assume the FOPT occurs at conformal time $\tau_*=\tau_{\rm eq}/10$ and BFDM comprises all of DM in the universe. The analytic solution in blue follows from \ref{['eq:G+case1']} and is derived in radiation dominated universe.
  • Figure 2: The total matter power spectrum, linearly evolved until today, for BFDM scenarios with various combinations of $f_{\rm BF}$ and $\tau_*$ parameters (colored curves) and fixed $\beta/H_* = 100$. The $\Lambda$CDM model is shown in black, together with the data points from the observations of SDSS LRG in pink and BOSS Lyman-$\alpha$ in red Chabanier:2019eai.
  • Figure 3: Constraints on BFDM in the $f_{\rm BF}$ versus $\tau_*/\tau_{\rm eq}$ parameter space based on the matter power spectrum measurements made by SDSS (blue shaded region) and BOSS (yellow shaded region) for $\beta/H_* = 100$. The upcoming cosmological experiments based on spectroscopic and 21-cm surveys can greatly expand the sensitivity in the BFDM parameter space, as shown by the green and purple shaded regions, respectively.