# Four-Fermion Interaction Model on $\mathcal{M}^{D-1} \otimes S^1$

## TL;DR

This paper investigates how finite size effects influence chiral symmetry breaking in a four-fermion interaction model on a compactified spacetime, providing explicit expressions for the effective potential across dimensions.

## Contribution

It derives explicit effective potential expressions for the model on $ ext{M}^{D-1} imes S^1$ and analyzes the conditions for symmetry restoration and Casimir force sign change.

## Key findings

- Critical lines for phase transition are identified.
- Conditions for Casimir force sign-flip are established.
- Explicit effective potential formulas are provided for arbitrary dimensions.

## Abstract

Four-fermion interaction models are often used as simplified models of interacting fermion fields with the chiral symmetry. The chiral symmetry is dynamically broken for a larger four-fermion coupling. It is expected that the broken symmetry is restored under extreme conditions. In this paper, the finite size effect on the chiral symmetry breaking is investigated in the four-fermion interaction model. We consider the model on a flat spacetime with a compactified spatial coordinate, $\mathcal{M}^{D-1} \otimes S^1$ and obtain explicit expressions of the effective potential for arbitrary spacetime dimensions in the leading order of the $1/N$ expansion. Evaluating the effective potential, we show the critical lines which divide the symmetric and the broken phase and the sign-flip condition for the Casimir force.