  Astrophysical searches for new long-range interactions complement collider
searches for new short-range interactions. Conveniently, neutrino flavor
oscillations are keenly sensitive to the existence of long-ranged flavored
interactions between neutrinos and electrons, motivated by lepton-number
symmetries of the Standard Model. For the first time, we probe them using
TeV-PeV astrophysical neutrinos and accounting for all large electron
repositories in the local and distant Universe. The high energies and colossal
number of electrons grant us unprecedented sensitivity to the new interaction,
even if it is extraordinarily feeble. Based on IceCube results for the flavor
composition of astrophysical neutrinos, we set the ultimate bounds on
long-range neutrino flavored interactions.
