Addressing the Hubble tension with Sterile Neutrino Dark Matter

Abstract

One of the promising dark matter (DM) candidates is a keV scale sterile neutrino. In the early universe the observed relic of the sterile neutrino DM is generated via the \textit{Dodelson-Widrow} mechanism. However, this production scenario is severely constraint by various astrophysical observations. Many non-standard interactions between active ($ν_a$) and sterile ($ν_s$) neutrino have been proposed to evade these astrophysical bounds. Here, we study sterile neutrino in the context of a mass-varying scenario by coupling both active and sterile neutrino to a scalar field. This novel mechanism opens up a new parameter space that generates the observed DM relic and alleviates the \textit{Hubble tension}. We find that the resulting parameter space can be fully probed by future X-ray missions.

Figures (5)

• Figure 1: Evolution of the scalar field for $\phi_0/M_{\text{pl}}$ = 0.8 and coupling, $\epsilon = 1.56\times 10^3$. Here, sterile neutrino mass is 10 keV and effective mass is 10 MeV. The vertical line is at $z_{\text{osc}} = 1.81\times 10^6$.
• Figure 2: Yield of sterile neutrino for present day sterile mass of $m_{\nu_{4}} = 10 \, \text{keV}$. Increasing $m^{\text{max}}_{\nu_{4},\, \text{eff}}$ by one order leads to production at higher temperature and reduce vacuum mixing angle by one order.
• Figure 3: Evolution of extra energy density ($\rho_{\text{extra}}$) as a ratio of $\rho_{\Lambda\text{CDM}}$ for $\phi_0/M_{\text{pl}}$ = 0.8 and coupling, $\epsilon = 1.56\times 10^3$. Here, present day sterile neutrino mass is 10 keV and effective mass is 10 MeV. $\rho_{\text{extra}}$ has of the order $\rho_{\Lambda\text{CDM}}$ contribution in the redshift range $z \approx 10^7-10^3$.
• Figure 4: Scalar field parameter space for $m_{\nu_4}$ = 10 keV. Each contour line corresponds to different $m^{\text{max}}_{\nu_4, \text{eff}}/m_{\nu_4}$ and satisfies the DM relic, $\Omega_{\text{DM}} h^2 = 0.12$ for specific values of $\sin^2{2\theta}$. $H_0$ value increases when we go left to right along each contour. We have marked SH0ES 1-$\sigma$ and 2-$\sigma$ regions by orange and cyan color respectively. Below $m^{\text{max}}_{\nu_4 ,\text{eff}} / m_{\nu_4} = 1.3 \times 10^3$ marked by steelblue shaded region is excluded by X-ray observations. Above $m^{\text{max}}_{\nu_4 ,\text{eff}} / m_{\nu_4} = 8.8 \times 10^3$ hatched region is excluded by BBN.
• Figure 5: Sterile neutrino parameter space in presence of our new interaction term. In the white region DM relic and Hubble tension both can be satisfied. The black dotted and gray solid lines correspond to relic line for $m^{\text{max}}_{\nu_4 , \text{eff}} / m_{\nu_4} = 10^3$ and $8.8 \times 10^3$ respectively. X-ray and Lyman-$\alpha$ bounds are denoted by steelblue and light yellow region respectively. The sensitivity curves of future X-ray missions Dev:2025 are shown in green(ATHENA), in blue( eXTP), and in orange(eROSITA). The black solid line is the standard Dodelson-Widrow line.