Dark radiation

Dark radiation is a postulated species of radiation that mediates interactions in the dark sector. That is, just the way photons mediate electromagnetic interactions between particles in the Standard Model (baryonic matter in cosmology), dark radiation is supposed to mediate interactions between dark matter particles.^[1] And, similar to dark matter particles, dark radiation doesn't interact with Standard Model particles. Though there has been no notable evidence for the existence of such a species, since the baryonic sector contains multiple interacting species, it is reasonable that the dark sector also does. Moreover, it has been pointed out recently that the cosmic microwave background data seem to suggest that the number of effective neutrino degrees of freedom is more than 3.046, which is the standard case for 3 species of neutrinos.^[2] This extra degree of freedom could arise from having a non-trivial amount of dark radiation in the universe. One possible candidate for dark radiation is a sterile neutrino.

See also

• Dark photon

References

Dark matter Forms of dark matter Baryonic dark matter Cold dark matter Hot dark matter Light dark matter Mixed dark matter Warm dark matter Self-interacting dark matter Hypothetical particles Axino Axion Dark photon Holeum LSP Minicharged particle Neutralino Sterile neutrino SIMP WIMP Theories and objects Cuspy halo problem Dark fluid Dark galaxy Dark matter halo Dark radiation Dark star Dwarf galaxy problem ELKO field Halo mass function Massive compact halo object Mirror matter Navarro–Frenk–White profile Scalar field dark matter Search experiments Direct detection ANAIS ArDM ADMX CDEX CDMS CoGeNT COUPP CRESST DAMA/LIBRA DAMA/NaI DarkSide DEAP DMTPC DRIFT EDELWEISS EURECA KIMS LUX LZ PandaX PICASSO SIMPLE UKDMC WARP XENON ZEPLIN-III Indirect detection AMS-02 ATIC CAST IceCube MOA OGLE PAMELA Other projects MultiDark PVLAS SNOLAB Potential dark galaxies HE0450-2958 HVC 127-41-330 Smith's Cloud VIRGOHI21 Related Galaxy formation and evolution Illustris project