Coupled Potts models: Self-duality and fixed point structure

TL;DR

This paper investigates coupled q-state Potts models, identifying non-trivial fixed points through numerical simulations, and characterizes their critical behavior with novel algorithms and comparisons to perturbative predictions.

Contribution

It introduces new transfer matrix algorithms to accurately compute critical exponents and central charges for coupled Potts models, confirming the existence of fixed points predicted by RG analysis.

Findings

Existence of non-trivial fixed points for 2 <= q <= 4

Accurate determination of central charge and multiscaling exponents

Confirmation of criticality through eigenvalue analysis and scaling laws

Abstract

We consider q-state Potts models coupled by their energy operators. Restricting our study to self-dual couplings, numerical simulations demonstrate the existence of non-trivial fixed points for 2 <= q <= 4. These fixed points were first predicted by perturbative renormalisation group calculations. Accurate values for the central charge and the multiscaling exponents of the spin and energy operators are calculated using a series of novel transfer matrix algorithms employing clusters and loops. These results compare well with those of the perturbative expansion, in the range of parameter values where the latter is valid. The criticality of the fixed-point models is independently verified by examining higher eigenvalues in the even sector, and by demonstrating the existence of scaling laws from Monte Carlo simulations. This might be a first step towards the identification of the conformal field theories describing the critical behaviour of this class of models.