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Dark Walker in the Early Universe: A Strongly Coupled Sector Model

Chen Yang

Abstract

We explore the phenomenology of the ``Dark Walker'' -- an $\text{SU}(3)$ theory with eight flavors of massless fundamental fermions in the dark sector. During inflation, its walking dynamics generate primordial non-Gaussianities through the exchange of unparticles, while accounting for the current dark matter relic abundance if we consider freeze-in of Dark Walker coupled to the Standard Model through the Higgs portal. This provides a simple yet predictive example linking strongly coupled inflationary dynamics to present-day dark matter.

Dark Walker in the Early Universe: A Strongly Coupled Sector Model

Abstract

We explore the phenomenology of the ``Dark Walker'' -- an theory with eight flavors of massless fundamental fermions in the dark sector. During inflation, its walking dynamics generate primordial non-Gaussianities through the exchange of unparticles, while accounting for the current dark matter relic abundance if we consider freeze-in of Dark Walker coupled to the Standard Model through the Higgs portal. This provides a simple yet predictive example linking strongly coupled inflationary dynamics to present-day dark matter.

Paper Structure

This paper contains 1 section, 32 equations, 4 figures.

Table of Contents

  1. Calculation of non-Gaussianity

Figures (4)

  • Figure 1: The $\beta$-function with merged fixed points
  • Figure 2: The contour plot of $f_{\text{NL},\psi}$ at $O(1)$ for a range of $H_{\text{inf}}$ and $\Lambda_{\text{cw}}$. The magnitude of $f_{\text{NL}}$ is sensitive to the value of $H_{\text{inf}}$.
  • Figure 3: Shape functions for $\Delta=1.8$ and $\Delta=3.9$. We rescale the magnitudes by $10^2$ for $\Delta=1.8$ and $10^3$ for $\Delta=3.9$ to set the plot value within $O(1)$.
  • Figure 4: The relation between the DM particle mass and the Wilson coefficient $\lambda$. The yellow region is the permitted mass range with respect to $T_R$. We take $\Lambda_{\text{cw}}$ to be the lowest value, in order to find the widest mass range. The blue regions are excluded by the Bullet Cluster observations, inflationary Hubble constant and DM lifetime.