Report of the Topical Group on Cosmic Probes of Fundamental Physics for for Snowmass 2021

Understand

Cosmic Probes of Fundamental Physics take two primary forms: Very high energy particles (cosmic rays, neutrinos, and gamma rays) and gravitational waves.

• Already today, these probes give access to fundamental physics not available by any other means, helping elucidate the underlying theory that completes the Standard Model.
• The last decade has witnessed a revolution of exciting discoveries such as the detection of high-energy neutrinos and gravitational waves.
• The scope for major developments in the next decades is dramatic, as we detail in this report.