$1/N$ expansion of the D3-D5 defect CFT

TL;DR

This paper analyzes the $1/N$ expansion of a defect conformal field theory involving D3-D5 branes, using matrix models and integrable hierarchies to explore strong coupling regimes and higher-order corrections.

Contribution

It introduces a systematic method to study the $1/N$ expansion of the D3-D5 defect CFT at any coupling using integrable hierarchies and extends the analysis to $SU(N)$ gauge symmetry.

Findings

Strong coupling regime determined by differential relations.

$1/N$ expansion systematically studied at all couplings.

Extension of analysis to $SU(N)$ gauge symmetry.

Abstract

We consider four dimensional $U(N)$ $\mathcal N=4$ SYM theory interacting with a 3d $\mathcal N=4$ theory living on a codimension-one interface and holographically dual to the D3-D5 system without flux. Localization captures several observables in this dCFT, including its free energy, related to the defect expectation value, and single trace $\frac{1}{2}$-BPS composite scalars. These quantities may be computed in a hermitian one-matrix model with non-polynomial single-trace potential. We exploit the integrable Volterra hierarchy underlying the matrix model and systematically study its $1/N$ expansion at any value of the 't Hooft coupling. In particular, the strong coupling regime is determined -- up to non-perturbative exponentially suppressed corrections -- by differential relations that constrain higher order terms in the $1/N$ expansion. The analysis is extended to the model with $SU(N)$ gauge symmetry by resorting to the more general Toda lattice equations.