Dark Light, Dark Matter and the Misalignment Mechanism

TL;DR

The paper investigates a very light vector boson with a Stueckelberg mass as a dark matter candidate produced by inflationary misalignment and kinetically mixed with the photon. It derives cosmological and laboratory bounds on the kinetic mixing parameter $\chi$ and maps observable signatures, including weak EM fields and potential apparent drift in fundamental constants, as well as the possibility of adiabatic conversion in plasma-rich environments. A key comparison with the Higgs mechanism shows misalignment production favors the Stueckelberg mass, while the parameter space is constrained by early-Universe dynamics and decays. Overall, the work identifies regions of $(M,\chi)$ that yield a viable, detectable vector dark matter with distinct experimental signatures.

Abstract

We explore the possibility that the dark matter is a condensate of a very light vector boson. Such a condensate could be produced during inflation, provided the vector mass arises via the Steuckelberg mechanism. We derive bounds on the kinetic mixing of the dark matter boson with the photon, and point out several potential signatures of this model.

Figures (3)

• Figure 1: Mass mixing in plasma: The solid and dashed curves show the eigenvalues of the mass matrix as a function of the radial position inside the cluster. The dotted line shows the density of the ionized gas in the cluster also as a function of the radial position. In order to make the level crossing visible we have adopted $M=10^{-12}\:\mathrm{eV}$ and $\chi=0.2$.
• Figure 2: Summary of Constraints: The early Universe behavior puts a dominant bound on $\chi$ in the higher mass range, for $M>2m_e$ the bounds are dominated by decays. The Shaded region called AdC marks the possible combinations of $(\chi,M)$ that could lead to adiabatic conversions. We have marked out the projection of the limits that can be achieved by ADMX ADMX(Orange) - axion search experiment turned into a light shinning through the wall experiment. The bounds put by shaded regions with dotted lines come from a summary by Goodsell and comprise the bounds by both theoretical and experimental considerations such as lifetime of the Sun (Red), Horizontal branch Star limits (Green), Coulomb law tests (Blue), CMB pollution by the dark photon (Yellow) and beam dump experiments E141 and E137 (Purple). In the low mass region the dominant bound comes from the drift of fine structure constant (blue, solid/dashed).
• Figure :