Momentum Fractionation on Superstrata

TL;DR

This paper constructs the first smooth, horizonless supergravity solutions called superstrata that holographically realize momentum fractionation in D1-D5 CFT states, advancing understanding of black-hole microstates.

Contribution

It introduces a method to generate asymptotically-flat superstrata solutions that encode momentum fractionation, linking CFT states to smooth supergravity geometries.

Findings

Constructed the first asymptotically-flat superstrata solutions.

Demonstrated these solutions are dual to CFT states with fractional momentum.

Showed large classes of momentum-fractionated CFT states can be realized as smooth geometries.

Abstract

Superstrata are bound states in string theory that carry D1, D5, and momentum charges, and whose supergravity descriptions are parameterized by arbitrary functions of (at least) two variables. In the D1-D5 CFT, typical three-charge states reside in high-degree twisted sectors, and their momentum charge is carried by modes that individually have fractional momentum. Understanding this momentum fractionation holographically is crucial for understanding typical black-hole microstates in this system. We use solution-generating techniques to add momentum to a multi-wound supertube and thereby construct the first examples of asymptotically-flat superstrata. The resulting supergravity solutions are horizonless and smooth up to well-understood orbifold singularities. Upon taking the AdS3 decoupling limit, our solutions are dual to CFT states with momentum fractionation. We give a precise proposal for these dual CFT states. Our construction establishes the very nontrivial fact that large classes of CFT states with momentum fractionation can be realized in the bulk as smooth horizonless supergravity solutions.