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Gravitational waves from deflagration bubbles in first-order phase transitions

Ariel Megevand

TL;DR

The paper analyzes gravitational waves produced by turbulence during a cosmological first-order phase transition that proceeds via deflagration bubbles. It accounts for the unique dynamics of deflagrations, including a leading shock front that reheats the plasma and influences bubble growth, and develops a framework to estimate the GW signal from the resulting turbulence using a Kolmogorov spectrum and an analytic expression for energy transfer efficiency. The authors derive how the GW spectrum depends on latent heat, bubble separation, and wall velocity, showing that peak signals of order   10^{-9} are possible and may lie in the LISA band for electroweak-scale transitions with favorable parameters. They provide practical criteria for detectability (e.g., T_*  100 GeV, d/H_*^{-1}  10^{-2}, v_w  10^{-2},    0.1) and offer analytical tools to incorporate deflagration GW production into numerical phase-transition studies, highlighting the importance of turbulence over bubble collisions in this scenario.

Abstract

The walls of bubbles in a first-order phase transition can propagate either as detonations, with a velocity larger than the speed of sound, or deflagrations, which are subsonic. We calculate the gravitational radiation that is produced by turbulence during a phase transition which develops via deflagration bubbles. We take into account the fact that a deflagration wall is preceded by a shock front which distributes the latent heat throughout space and influences other bubbles. We show that turbulence can induce peak values of $Ω_{GW}$ as high as $\sim 10^{-9}$. We discuss the possibility of detecting at LISA gravitational waves produced in the electroweak phase transition with wall velocities $v_w\lesssim 10^{-1}$, which favor electroweak baryogenesis.

Gravitational waves from deflagration bubbles in first-order phase transitions

TL;DR

The paper analyzes gravitational waves produced by turbulence during a cosmological first-order phase transition that proceeds via deflagration bubbles. It accounts for the unique dynamics of deflagrations, including a leading shock front that reheats the plasma and influences bubble growth, and develops a framework to estimate the GW signal from the resulting turbulence using a Kolmogorov spectrum and an analytic expression for energy transfer efficiency. The authors derive how the GW spectrum depends on latent heat, bubble separation, and wall velocity, showing that peak signals of order   10^{-9} are possible and may lie in the LISA band for electroweak-scale transitions with favorable parameters. They provide practical criteria for detectability (e.g., T_*  100 GeV, d/H_*^{-1}  10^{-2}, v_w  10^{-2},    0.1) and offer analytical tools to incorporate deflagration GW production into numerical phase-transition studies, highlighting the importance of turbulence over bubble collisions in this scenario.

Abstract

The walls of bubbles in a first-order phase transition can propagate either as detonations, with a velocity larger than the speed of sound, or deflagrations, which are subsonic. We calculate the gravitational radiation that is produced by turbulence during a phase transition which develops via deflagration bubbles. We take into account the fact that a deflagration wall is preceded by a shock front which distributes the latent heat throughout space and influences other bubbles. We show that turbulence can induce peak values of as high as . We discuss the possibility of detecting at LISA gravitational waves produced in the electroweak phase transition with wall velocities , which favor electroweak baryogenesis.

Paper Structure

This paper contains 6 sections, 31 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Phase transition dynamics
  3. Turbulence from deflagration bubbles
  4. Relic gravitational waves
  5. Gravitational radiation from the phase transition
  6. Conclusions

Figures (1)

  • Figure 1: The values of $\alpha$ and $T_*$ that give $f_p=1mHz$ and $\Omega _{GW}(f_p)=10^{-11}$, for $v_i=0.1$ (solid line), $v_i=0.05$ (dashed line) and $v_i=0.02$ (dotted line).