Three Merry Roads to T-Violation

TL;DR

This paper explores three fundamental approaches to T-violation in physics, highlighting their underlying symmetry principles and potential extensions beyond the standard model.

Contribution

It categorizes the main approaches to T-violation, providing a unified framework based on symmetry principles and illustrating each with examples.

Findings

Identifies three core approaches to T-violation.

Provides a symmetry-based template for detecting T-violation.

Discusses potential extensions beyond the standard model.

Abstract

This paper is a tour of how the laws of nature can distinguish between the past and the future, or be T-violating. I argue that, in terms of the basic argumentative structure, there are really just three approaches currently being explored. I show how each is characterized by a symmetry principle, which provides a template for detecting T-violating laws even without knowing the laws of physics themselves. Each approach is illustrated with an example, and the prospects of each are considered in extensions of particle physics beyond the standard model.