Enhancing non-melonic triangulations: A tensor model mixing melonic and planar maps

TL;DR

This paper explores how non-melonic contributions in tensor models can be enhanced to produce new large N limits, revealing phases like branched polymers and 2D quantum gravity, with explicit calculations and non-perturbative analysis.

Contribution

It demonstrates the consistent enhancement of non-melonic interactions in tensor models, leading to new large N limits and phases, with explicit combinatorial and analytical results.

Findings

Existence of 1/N expansion for enhanced non-melonic models

Identification of branched polymer and 2D quantum gravity phases

Analyticity of the model in coupling constants within cardioid domains

Abstract

Ordinary tensor models of rank $D\geq 3$ are dominated at large $N$ by tree-like graphs, known as melonic triangulations. We here show that non-melonic contributions can be enhanced consistently, leading to different types of large $N$ limits. We first study the most generic quartic model at $D=4$, with maximally enhanced non-melonic interactions. The existence of the $1/N$ expansion is proved and we further characterize the dominant triangulations. This combinatorial analysis is then used to define a non-quartic, non-melonic class of models for which the large $N$ free energy and the relevant expectations can be calculated explicitly. They are matched with random matrix models which contain multi-trace invariants in their potentials: they possess a branched polymer phase and a 2D quantum gravity phase, and a transition between them whose entropy exponent is positive. Finally, a non-perturbative analysis of the generic quartic model is performed, which proves analyticity in the coupling constants in cardioid domains.