Ultra-light Dark Matter Limits from Astrophysical Neutrino Flavor

Ultra-light dark matter is a class of dark matter models where the mass of the dark matter particle is very small and the dark matter behaves as a classical field pervading our galaxy. If astrophysical neutrinos interact with ultra-light dark matter, these interactions would produce a matter potential in our galaxy which may cause anomalous flavor conversions. Recently, IceCube high-energy starting event flavor measurements are used to set stringent limits on isotropic Lorentz violating fields under the Standard-Model Extension framework. We apply the IceCube Lorentz violation limits to set limits on neutrino - ultra-light dark matter couplings. We assume the dark matter field undergoes fast oscillations in our galaxy, yielding neutrino interactions with dark matter that broaden and smear the observed flavor structure of astrophysical neutrinos at IceCube. The constraints we obtain are an order of magnitude tighter than current and future terrestrial neutrino experimental limits. The sensitivity of ultra-light dark matter can be further improved in the near future by new particle identification algorithms in IceCube and the emergence of next-generation neutrino telescopes.