100 years of spin: fundamental physics, dark matter, exotic interactions, and all that

TL;DR

This paper reviews the historical and current significance of spin in probing fundamental physics, including tests of symmetries, dark matter searches, and exotic interactions.

Contribution

It provides a comprehensive reflection on spin's role in modern physics, highlighting recent advances and ongoing research in fundamental questions.

Findings

Spin has been crucial in testing CP and CPT symmetries.

Searches for exotic spin-dependent interactions relate to dark matter.

Spin-based experiments continue to offer new insights into fundamental physics.

Abstract

For a century, spin has been an indispensable probe of the fundamental laws of nature. A reflection on the role of spin in shaping modern physics is presented, from the early days of quantum mechanics to the latest precision tests of the Standard Model. The significance of magnetic and electric dipole moments in testing CP and CPT symmetries is surveyed, along with the ongoing searches for exotic spin-dependent interactions that may reveal the nature of dark matter and its connection to spacetime geometry. Through these vignettes, it is shown that spin continues to provide a fresh perspective on the most profound questions in physics today.