Bounds on Very Weakly Interacting Sub-eV Particles (WISPs) from   Cosmology and Astrophysics
  Many weakly interacting sub-electronVolt particles (WISPs) are easily accommodated in extensions of the standard model. Generally the strongest bounds on their existence come from stellar evolution and cosmology, where to the best of our knowledge observations seem to agree with the standard budget of particles. In this talk I review the most demanding constraints for axions and axion-like-particles, hidden photons and mini-charged particles. 
Javier Redondo