The Hubble diagram as a probe of mini-charged particles

TL;DR

This paper addresses whether mini-charged particles (MCPs) could modify the cosmological luminosity-distance relation and bias the inferred energy content of the Universe. It models MCP-induced dimming via photon-pair production in intergalactic magnetic fields, deriving $P(z)=\exp\left(-\int_0^z{\rm d}\ell\,\Gamma_{\rm B}(\omega)\right)$ and its impact on $d_L^{\rm obs}(z)=d_L(z)/\sqrt{P(z)}$, and uses SN Ia data to place bounds on $\epsilon$ for $m_\epsilon\lesssim 10^{-7}$ eV, finding $\epsilon \lesssim 4\times 10^{-9}$. The work also explores a hypothetical strong-dimming scenario as a replacement for dark energy, showing that achromatic color constraints challenge such a model. Overall, the results provide competitive MCP bounds and highlight how MF mixing and new light sectors can influence SN-based cosmology.

Abstract

The luminosity-redshift relation of cosmological standard candles provides information about the relative energy composition of our Universe. In particular, the observation of type Ia supernovae up to redshift of z~2 indicate a universe which is dominated today by dark matter and dark energy. The propagation distance of light from these sources is of the order of the Hubble radius and serves as a very sensitive probe of feeble inelastic photon interactions with background matter, radiation or magnetic fields. In this paper we discuss the limits on mini-charged particle models arising from a dimming effect in supernova surveys. We briefly speculate about a strong dimming effect as an alternative to dark energy.

Figures (2)

• Figure 1: Upper Panel: Hubble diagram showing the SNe Ia 'union' compilation from Ref. Kowalski:2008ez. The luminosity distance $d_L$ is shown by the difference $\Delta(m-M)$ to an empty $\Omega_{\rm tot}=0$ flat universe. We show the effect of an MCP spinor with two different combinations of $m_\epsilon$ and $\epsilon$ on the luminosity distance of sources observed in a frequency interval centered at $\omega_\star$. Lower Panel: The reduced $\chi^2$ of the SNe Ia 'union' compilation Kowalski:2008ez with MCP production in the limit $m_\epsilon\to0$ assuming a 'replenishing' ($\beta=0$) and an 'adiabatic' ($\beta=2$) IG magnetic field. We show the deviation $\Delta\chi^2$/d.o.f. $=25$ relative to the $\Lambda$CDM model indicating the strength of a $5\sigma$-deviation. The MCP model is parametrized by the combination $\epsilon\times{\rm B_{IG, nG}^{1/4}}\times\omega_{\star,\rm eV}^{-1/8}\times h_{0.70}^{-3/8}\times a_+^{3/8}$ in the massless limit.
• Figure 2: As upper panel of Fig. \ref{['dimming']}, but now showing also a flat CDM model with $\Omega_m=1$ and $\Omega_\Lambda=0$. We consider a mini-charged Dirac spinor with charge $\epsilon=3.1\times10^{-9}$ and mass $m_\epsilon\ll10^{-7}$ eV and show the dimming for the B ($\lambda_\star\simeq440$ nm, lower line) and V ($\lambda_\star\simeq550$ nm, upper line) band. We also assume an adiabatically expanding ($\beta=2$) IG magnetic field with strength B=$1$ nG. The (absolute) relative difference of $\Delta(m-M)$ between the B and V band is $\lesssim0.06$ for $z\lesssim1.8$.