D-Instantons on the boundary

TL;DR

This work investigates how D(-1) branes in the AdS5×S^5 background realize boundary instantons within the AdS/CFT correspondence. By constructing localized D(-1) solutions with a harmonic function $H_{-1}$, the authors show that the dilaton profile on the boundary reproduces four-dimensional Yang–Mills instanton data, with the bulk radial coordinate $z$ acting as an ultraviolet regulator for instanton size. The instanton moduli space naturally emerges as an $AdS_5$-type space with measure $d\mu = \frac{d^4x\,dz}{z^5}$, and the analysis extends to D1–D5 systems yielding two-dimensional instantons with measure $d\mu = \frac{d^2x\,dz}{z^3}$, highlighting a consistent bulk–boundary dictionary for instanton sectors. The results reinforce the geometric realization of boundary instantons in holography and suggest avenues to connect with ADHM multi-instanton constructions and brane-based computations of instanton observables. Overall, the paper strengthens the holographic picture that bulk D-instantons encapsulate boundary instanton physics in both four and two dimensions.

Abstract

The Maldacena's proposal has established an intriguing connection between string theory in AdS spaces and gauge theory. In this paper we study the effects of adding D(-1)-branes to the system of D3- or (D1-D5)-branes and we give arguments indicating that D(-1)-branes are necessary to describe four and two dimensional instantons.