Events Daily

Monday, March 25, 2024
      

Exciting nu physics below an MeV
Neal Weiner, New York University
Event Type: CCPP Brown Bag
Time: 12:30 PM - 1:30 PM
Location: 726 Broadway, 940, CCPP Seminar
Abstract: Cosmology is directly sensitive to the different components of the universe at temperatures from eV to MeV. Big Bang Nucleosynthesis tells us no other states were in equilibrium just above that range, but could something dramatic happen inside of it? I will sketch out the basic physics of neutrino oscillations and oscillations into dark sectors and discuss under what conditions a dark sector might equilibrate at “late" times, and possible observable consequences.

Axion dark matter from inflation-driven quantum phase transition
Bingrong Yu, Cornell University
Event Type: Informal HEP Talk
Time: 2:00 PM - 3:00 PM
Location: 726 Broadway, 940, CCPP Seminar
Abstract: We propose a new mechanism to produce axion dark matter from inflationary fluctuations. Quantum fluctuations during inflation are strengthened by a coupling of the axion kinetic term to the inflaton. This coupling acts as an order parameter, breaking the scale invariance of the axion power spectrum and driving a quantum phase transition. A red-tilted spectrum leads to an exponential enhancement of the axion abundance as the comoving horizon shrinks during inflation. This enhancement allows sufficient axion production to comprise the entire dark matter abundance, despite the ultralight mass. Our mechanism predicts a significantly different parameter space from the usual misalignment mechanism, allowing much larger couplings to Standard Model particles, which can be probed by future axion experiments. It is applicable to both QCD axion and axion-like particles.