Hidden Photon Dark Matter Interacting via Axion-like Particles
  We investigate a scenario where the dark matter of the Universe is made from
very light hidden photons transforming under a $Z_{2}$-symmetry. In contrast to
the usual situation, kinetic mixing is forbidden by the symmetry and the dark
photon interacts with the Standard Model photon only via an axion-like particle
acting as a "messenger". Focusing on signatures involving the ordinary photon,
our survey of the phenomenology includes limits from cosmological stability,
CMB distortions, astrophysical energy loss, light-shining-through-walls
experiments, helioscopes and solar X-ray observations.
