Big Bang Nucleosynthesis in the presence of sterile neutrinos with   altered dispersion relations
  Big Bang Nucleosynthesis imposes stringent bounds on light sterile neutrinos mixing with the active flavors. Here we discuss how altered dispersion relations can weaken such bounds and allow compatibility of new sterile neutrino degrees of freedom with a successful generation of the light elements in the early Universe. 
Elke Aeikens, Heinrich P\"as, Sandip Pakvasa, Thomas J. Weiler
hep-ph astro-ph.CO nucl-th