[Triumf-seminars] TRIUMF Theory Seminar today at 13:00

TRIUMF Seminars triumf-seminars at lists.triumf.ca
Tue Dec 6 05:00:02 PST 2016


Date/Time: Tue 2016-12-06 at 13:00

Location:  Theory Room         

Speaker:   Nicholas Orlofsky (U Michigan)

Title:     High-Scale Axions with Isocurvature from Inflationary Dynamics

Abstract: The axion is an elegant solution to the strong CP problem and an attractive candidate for dark matter.  Axion cosmology depends on when Peccei-Quinn (PQ) symmetry is spontaneously broken.  If PQ symmetry breaking occurs before inflation ends, the axion obtains fluctuations that lead to isocurvature perturbations in the cosmic microwave background (CMB).  These isocurvature perturbations are larger for inflation occurring at higher energy scales.  An observation of primordial tensor modes at near-future CMB experiments would point to a high scale of inflation.  If such a detection were made, CMB constraints on isocurvature would naively rule out QCD axion dark matter with a large PQ-breaking scale.  This assumes the potential of the axion is unmodified during inflation.  
I will revisit models where inflationary dynamics modify the axion potential and discuss how isocurvature bounds can be relaxed.  I will show that models that rely solely on a larger PQ-breaking scale during inflation f_I require either late-time dilution of the axion abundance or highly super-Planckian f_I that somehow does not dominate the inflationary energy density.  Models that have enhanced explicit breaking of the PQ symmetry during inflation may allow a PQ breaking scale close to the Planck scale.  Avoiding disruption of inflationary dynamics provides important limits on the parameter space.





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