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Hot and heavy dark matter from a weak scale phase transition

by Iason Baldes, Yann Gouttenoire, Filippo Sala

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Submission summary

Authors (as registered SciPost users): Iason Baldes · Filippo Sala
Submission information
Preprint Link: scipost_202208_00026v1  (pdf)
Date submitted: Aug. 14, 2022, 7:17 p.m.
Submitted by: Iason Baldes
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
Specialties:
  • Gravitation, Cosmology and Astroparticle Physics
  • High-Energy Physics - Phenomenology
Approaches: Theoretical, Phenomenological

Abstract

We point out that dark matter which is produced non-adiabatically in a phase transition (PT) with fast bubble walls receives a boost in velocity which leads to long free-streaming lengths. We find that this could be observed via the suppressed matter power spectrum for dark matter masses around $10^8 - 10^9$ GeV and energy scales of the PT around $ 10^{2} - 10^3$~GeV. The PT should take place at the border of the supercooled regime, i.e.~approximately when the Universe becomes vacuum dominated. This work offers novel physics goals for galaxy surveys, Lyman-$\alpha$, lensing, and 21-cm observations, and connects these to the gravitational waves from such phase transitions, and more speculatively to possible telescope signals of heavy dark matter decay.

Current status:
Has been resubmitted

Reports on this Submission

Report #2 by Anonymous (Referee 2) on 2022-9-28 (Invited Report)

  • Cite as: Anonymous, Report on arXiv:scipost_202208_00026v1, delivered 2022-09-28, doi: 10.21468/SciPost.Report.5788

Strengths

The authors are interested in the production of super-heavy, non-cold dark matter during a first order cosmological phase transition and the associated signatures. This dark matter production mechanism has been studied over the last few years by other groups. In the work under consideration, the authors emphasize how the dark matter will be produced with a large boost in the early universe, and even at the time of radiation-matter equality, the dark matter may have a non-negligible speed. This implies that the scenario can be constrained by probes of dark matter substructure, such as Lyman-alpha forest observations. Additionally, the authors derive predictions for the stochastic gravitational wave radiation that would be generated at the first order phase transition, and argue that this signal may be within reach of future space-based interferometer experiment LISA.

Weaknesses

1 -- The authors build upon earlier results [40-42], which I haven't studied carefully. I find it remarkable that the dark matter can acquires a Lorentz factor in the plasma frame that's as large as \gamma_{xp} ~ m_{DM} / T_n ~ 10^6 - 10^8. I suppose that the momentum kick comes from the patch of domain wall where the particle collided? I wonder whether this wouldn't have a large back reaction on the dynamics of the wall. If the impacts were sufficiently spread out, would the wall be driven away from a planar configuration? Anyway, this is hardly a shortcoming of the current paper, but rather my own confusion about [40-42].

Report

In my view the manuscript meets the journal's expectations for publication. The analysis is comprehensive and thorough. The idea is novel and provides avenues for future research. The manuscript is well-written and organized clearly. (I particularly appreciate that the authors were able to consolidate many of the details into appendices, so as to allow the main message to come through more clearly in the body of the paper.). I am happy to recommend the article for publication.

Requested changes

1 -- One thought. A recent study ( https://arxiv.org/abs/2203.05750 ) reported a strong limit on ultra-light dark matter from ultra-faint dwarf galaxies. When the constraints are expressed as lower limits on the dark matter mass, the bound is roughly an order of magnitude stronger than existing limits from Lyman-alpha forest observations. Typically these types of measurements leads to limits on both ULDM and WDM (non-negligible velocity at RM equality). Do these observations of UFD galaxies provide meaningful constraints on the model that the authors study?

  • validity: high
  • significance: good
  • originality: high
  • clarity: top
  • formatting: excellent
  • grammar: perfect

Report #1 by Anonymous (Referee 1) on 2022-9-26 (Invited Report)

  • Cite as: Anonymous, Report on arXiv:scipost_202208_00026v1, delivered 2022-09-26, doi: 10.21468/SciPost.Report.5775

Report

This article discusses a very interesting scenario in which the dark matter is heavy and non-cold due to a supercooled phase transition. The authors perform a detailed and careful analysis on this subject, and show this scenario can be probed by future gravitational wave interferometers. I have two minor suggestions. 1) When calculating the gravitational wave, the authors only present one with Tn < Tinflation. I would suggest the authors add another benchmark point, with a different dark matter mass, reheating temperature, and Tn> Tinflation. 2) Can the authors comment briefly on the complementarity between different searches for this scenario? I think those will help the readers to get a more complete picture about this scenario.

  • validity: -
  • significance: -
  • originality: -
  • clarity: -
  • formatting: -
  • grammar: -

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