D-branes in Little String Theory

TL;DR

This paper provides a detailed analysis of D-branes in the near-horizon limit of NS5-branes, exploring their geometry, spectrum, and implications for little string theory and related gauge theories using exact conformal field theory methods.

Contribution

It introduces new exact CFT calculations of D-brane spectra and couplings in little string theory, connecting geometric, holographic, and gauge theory perspectives.

Findings

Computed the one-point functions for D-branes in NS5-brane backgrounds.

Confirmed the open string spectrum matches low-energy brane constructions.

Linked boundary states to the beta-function of N=2 gauge theories.

Abstract

We analyze in detail the D-branes in the near-horizon limit of NS5-branes on a circle, the holographic dual of little string theory in a double scaling limit. We emphasize their geometry in the background of the NS5-branes and show the relation with D-branes in coset models. The exact one-point function giving the coupling of the closed string states with the D-branes and the spectrum of open strings is computed. Using these results, we analyze several aspects of Hanany-Witten setups, using exact CFT analysis. In particular we identify the open string spectrum on the D-branes stretched between NS5-branes which confirms the low-energy analysis in brane constructions, and that allows to go to higher energy scales. As an application we show the emergence of the beta-function of the N=2 gauge theory on D4-branes stretching between NS5-branes from the boundary states describing the D4-branes. We also speculate on the possibility of getting a matrix model description of little string theory from the effective theory on the D1-branes. By considering D3-branes orthogonal to the NS5-branes we find a CFT incarnation of the Hanany-Witten effect of anomalous creation of D-branes. Finally we give an brief description of some non-BPS D-branes.