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arXiv · 2501.05448

Fortuity in the D1-D5 system

Chi-Ming Chang·Ying-Hsuan Lin·Haoyu Zhang
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Abstract

We reformulate the lifting problem in the D1-D5 CFT as a supercharge cohomology problem, and enumerate BPS states according to the fortuitous/monotone classification. Working in the deformed $T^4$ symmetric orbifold theory, we give precise definitions of monotone and fortuitous cohomology classes generalizing the definitions in \cite{Chang:2024zqi} and illustrate them in the $N=1$ theory. For $N=2$, we construct the cohomology explicitly and match it to the exact BPS partition function. We further describe how to assemble BPS states at smaller $N$ into BPS states at larger $N$, and interpret their holographic duals as black hole bound states and massive stringy excitations on smooth horizonless (e.g. Lunin-Mathur) geometries.

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Chi-Ming Chang, Ying-Hsuan Lin, Haoyu Zhang. 2025-01-09. Fortuity in the D1-D5 system. https://arxiv.org/abs/2501.05448

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