Speaker
Dr
Pranjal Trivedi
(University of Hamburg)
Description
Axion-like particles (ALPs) are leading dark matter
candidates originally motivated by the strong CP problem and also
arise in theories of string compactifications. I will present a
sensitive probe for ALPs or ultra-light dark matter - the
birefringence in the cosmic microwave background (CMB). Birefringence
arises from the oscillating ALPs' effective refractive index and is
also relevant for laboratory axion searches. Constraints on the
axion-photon coupling derived from birefringence of CMB polarization
lead to orders of magnitude improvement over prior constraints, with
further prospects for upcoming cosmological birefringence
observations. These limits, in hitherto unconstrained regions of the
coupling vs. ALP mass parameter-space, are independent of assumed
magnetic fields and relatively robust to ALP dark matter fraction.
Primary author
Dr
Pranjal Trivedi
(University of Hamburg)
Co-author
Prof.
Guenter Sigl
(University of Hamburg)
