A Hidden Microwave Background? -- signatures of photon-WISP oscillations in the CMB

Abstract

The existence and cosmological signatures of a relic background of very weakly interacting sub-eV particles (WISPs), produced by photon-WISP oscillations is reviewed.

Comments: 4 pages, to appear in the Proceedings of the 5th Patras Workshop on Axions, WIMPs and WISPs