# On Symmetry and Duality

## TL;DR

This paper proposes a schema for understanding dualities between physical theories as isomorphic representations of a shared core, distinguishing three types of symmetry: stipulated, accidental, and proper.

## Contribution

It introduces a novel schema for dualities, clarifying the relationship between symmetries and dual theories in physics.

## Key findings

- The schema aligns well with standard symmetry treatments.
- It differentiates three kinds of symmetry: stipulated, accidental, proper.
- Provides a unified account of dualities and symmetries in physical theories.

## Abstract

We advocate an account of dualities between physical theories: the basic idea is that dual theories are isomorphic representations of a common core. We defend and illustrate this account, which we call a Schema, in relation to symmetries. Overall, the account meshes well with standard treatments of symmetries. But the distinction between the common core and the dual theories prompts a distinction between three kinds of symmetry: which we call `stipulated', `accidental' and `proper'.