Un-twisting the NHEK with spectral flows

TL;DR

This paper demonstrates how to generate asymptotically flat NHEK spacetimes from AdS_3 x S^3 solutions using supergravity dualities, revealing non-perturbative deformations and potential dual field theories involving Melvin twists.

Contribution

It introduces a novel method to embed NHEK spacetimes in string theory via spectral flows and dualities, enabling exploration of their microscopic duals.

Findings

Constructed infinite family of asymptotically flat NHEK embeddings.

Identified non-perturbative flux cycle bubbling deformations.

Clarified the role of spectral flow techniques in solution generation.

Abstract

We show that the six-dimensional uplift of the five-dimensional Near-Horizon-Extremal-Kerr (NHEK) spacetime can be obtained from an AdS_3 X S^3 solution by a sequence of supergravity - but not string theory - dualities. We present three ways of viewing these pseudo-dualities: as a series of transformations in the STU model, as a combination of Melvin twists and T-dualities and, finally, as a sequence of two generalized spectral flows and a coordinate transformation. We then use these to find an infinite family of asymptotically flat embeddings of NHEK spacetimes in string theory, parameterized by the arbitrary values of the moduli at infinity. Our construction reveals the existence of non-perturbative deformations of asymptotically-NHEK spacetimes, which correspond to the bubbling of nontrivial cycles wrapped by flux, and paves the way for finding a microscopic field theory dual to NHEK which involves Melvin twists of the D1-D5 gauge theory. Our analysis also clarifies the meaning of the generalized spectral flow solution-generating techniques that have been recently employed in the literature.