New Physics with PeV Astrophysical Neutrino Beams

Astrophysical neutrinos allow us to access energies and baselines that cannot be reached by human-made accelerators, offering unique probes of new physics phenomena. This thesis aims to address the challenges currently facing searches for Beyond Standard Model (BSM) physics in the high-energy universe using astrophysical neutrinos, particularly in the contexts of flavor measurements and connections with dark matter.