# Pushing the Energy and Cosmic Frontiers with High-Energy Astrophysical Neutrinos

## TL;DR

High-energy astrophysical neutrinos detected by IceCube serve as unique probes for fundamental particle physics at energy scales and distances unreachable by other methods, enabling tests of physics beyond the Standard Model.

## Contribution

This paper reviews how IceCube neutrinos enable new tests of fundamental physics and demonstrates the transition from theoretical proposals to experimental reality.

## Key findings

- Neutrinos travel up to Gpc distances, providing long-baseline probes.
- Detection of TeV to PeV neutrinos opens new energy frontiers.
- Stringent tests of physics beyond the Standard Model are possible.

## Abstract

The astrophysical neutrinos recently discovered by the IceCube neutrino telescope have the highest detected neutrino energies --- from TeV to PeV --- and travel the longest distances --- up to a few Gpc, the size of the observable Universe. These features make them naturally attractive probes of fundamental particle-physics properties, possibly tiny in size, at energy scales unreachable by any other means. The decades before the IceCube discovery saw many proposals of particle-physics studies in this direction. Today, those proposals have become a reality, in spite of prevalent astrophysical unknowns. We showcase examples of studying fundamental neutrino physics at these scales, including some of the most stringent tests of physics beyond the Standard Model.