The phase diagram of $T\bar{T}$-deformed Yang-Mills theory on the sphere

TL;DR

This paper analyzes the phase structure of large-N $T\bar{T}$-deformed 2D Yang-Mills theory on a sphere, revealing a rich phase diagram with phase transitions driven by instanton effects and saddle point collisions.

Contribution

It provides the first detailed phase diagram of $T\bar{T}$-deformed Yang-Mills on the sphere, including the effects of deformation on known transitions and nonperturbative corrections.

Findings

Identification of a third-order phase transition analogous to Douglas-Kazakov transition.

Discovery of a new disordered phase separated by a critical line with a tricritical point.

Analysis of saddle point collisions leading to a second-order phase transition.

Abstract

We study the large-$N$ dynamics of $T\bar{T}$-deformed two-dimensional Yang-Mills theory at genus zero. The 1/$N$-expansion of the free energy is obtained by exploiting the associated flow equation and the complete phase diagram of the theory is derived for both signs of the rescaled deformation parameter $\tau$. We observe a third-order phase transition driven by instanton condensation, which is the deformed version of the familiar Douglas-Kazakov transition separating the weakly-coupled from the strongly-coupled phase. By studying said phases, we compute the deformation of both the perturbative sector and the Gross-Taylor string expansion. Nonperturbative corrections in $\tau$ drive the system into an unexplored disordered phase separated by a novel critical line meeting tangentially the Douglas-Kazakov one at a tricritical point. The associated phase transition is induced by the collision of large-$N$ saddle points, determining its second-order character.