Long-range multi-scalar models at three loops

TL;DR

This paper advances the understanding of long-range multi-scalar models by computing their three-loop beta functions, revealing critical properties and fixed points in various symmetry settings.

Contribution

It provides the first three-loop renormalization group analysis for long-range multi-scalar models with general quartic interactions.

Findings

Computed three-loop beta functions for long-range models.

Identified fixed points and critical exponents for various symmetry groups.

Extended the renormalization group analysis beyond previous two-loop results.

Abstract

We compute the three-loop beta functions of long-range multi-scalar models with general quartic interactions. The long-range nature of the models is encoded in a kinetic term with a Laplacian to the power $0<\zeta<1$, rendering the computation of Feynman diagrams much harder than in the usual short-range case ($\zeta=1$). As a consequence, previous results stopped at two loops, while six-loop results are available for short-range models. We push the renormalization group analysis to three loops, in an $\epsilon=4\zeta-d$ expansion at fixed dimension $d<4$, extensively using the Mellin-Barnes representation of Feynman amplitudes in the Schwinger parametrization. We then specialize the beta functions to various models with different symmetry groups: $O(N)$, $(\mathbb{Z}_2)^N \rtimes S_N$, and $O(N)\times O(M)$. For such models, we compute the fixed points and critical exponents.