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Imprint of matter-antimatter asymmetry on collapsing domain walls

Dipendu Bhandari, Debasish Borah, Indrajit Saha

Abstract

Spontaneous breaking of discrete symmetries play non-trivial role in many well-motivated particle physics models. However, it leads to a network of cosmologically unwanted domain walls (DWs) which can be made unstable by introducing a bias term in the scalar potential. In this letter, we provide a novel origin of such bias terms at finite temperature due to radiative corrections from a Dirac fermion with large asymmetry $\sim \mathcal{O}(0.1)$ in its number density. In addition to getting a new viable region of parameter space for collapsing DWs not explored previously and resulting gravitational waves (GWs) accessible at future experiments, the viability of the scenario crucially depends on the temperature of asymmetry generation too. This provides a unique way of probing both the amount of asymmetry and the corresponding temperature via future observations of GWs from collapsing DWs. The large asymmetry in the Dirac fermion can also have interesting implications for the observed baryon asymmetry as well as dark matter and large neutrino asymmetry.

Imprint of matter-antimatter asymmetry on collapsing domain walls

Abstract

Spontaneous breaking of discrete symmetries play non-trivial role in many well-motivated particle physics models. However, it leads to a network of cosmologically unwanted domain walls (DWs) which can be made unstable by introducing a bias term in the scalar potential. In this letter, we provide a novel origin of such bias terms at finite temperature due to radiative corrections from a Dirac fermion with large asymmetry in its number density. In addition to getting a new viable region of parameter space for collapsing DWs not explored previously and resulting gravitational waves (GWs) accessible at future experiments, the viability of the scenario crucially depends on the temperature of asymmetry generation too. This provides a unique way of probing both the amount of asymmetry and the corresponding temperature via future observations of GWs from collapsing DWs. The large asymmetry in the Dirac fermion can also have interesting implications for the observed baryon asymmetry as well as dark matter and large neutrino asymmetry.

Paper Structure

This paper contains 1 section, 25 equations, 3 figures.

Table of Contents

  1. Finite-temperature bias with non-zero chemical potential

Figures (3)

  • Figure 1: Gravitational wave peak amplitude as a function of peak frequency. The colored curves correspond to symmetry breaking occurring at different values of $v_{\phi}$. The color scale represents the minimum amount of asymmetry required at the injection temperature, indicated on the top axis. Here, $C_1=10^{-22}$ is fixed.
  • Figure 2: Parameter space in the $y$--$m_0$ plane corresponding to Fig. \ref{['fig:1']}. Keeping $C_1$ fixed, the different colored lines represent different values of $v_\phi$. The color scale indicates the annihilation temperature arising from the zero-temperature bias. This determines the minimum temperature before which the asymmetry must be injected to trigger an earlier annihilation.
  • Figure 3: Parameter space in the $y$--$m_0$ plane. The contours correspond to fixed asymmetry injection temperatures of $10^5$ GeV (solid), $130$ GeV (dashed), $1$ GeV (dotted). The regions within the contours can be probed by gravitational wave experiments as well as $\Delta N_{\rm eff}$ experiments, indicated by different colors. The comoving asymmetry $Y_{\Delta \chi}$ is kept at the maximum allowed value $\sim \mathcal{O}(0.1)$ for each of the injection temperatures.