Overview
- Physicists Rishav Roshan and Sudipta Show published a paper in Physical Review Letters proposing that a previously ignored right-handed (sterile) neutrino briefly dominated the early universe and changed its expansion.
- In their scenario the long-lived particle sped up cosmic expansion and delayed when lepton flavors became distinguishable, allowing a lighter right-handed neutrino to generate the observed matter–antimatter asymmetry through leptogenesis.
- The paper gives example mass scales to make the idea concrete: the decoupled heavy partner about 100 trillion times the proton mass and a lighter partner about 100 billion proton masses.
- The proposal cannot be tested in colliders and must be probed indirectly by searching for a characteristic 'kink' in the primordial gravitational-wave background with future observatories such as LISA and SKAO and by tighter neutrino-mass measurements.
- The model is peer-reviewed but remains hypothetical and undetected; laboratory advances in precision symmetry tests offer complementary context but do not directly confirm the heavy particle.