Scalar hair at the string-black-hole correspondence
- 1Università di Bari
- 2Istituto Nazionale di Fisica Nucleare, Sezione di Bari
Abstract
A bstract : We study static, spherically symmetric axion-dilaton solutions of the tree-level four-dimensional string effective action. Using the sigma-model structure of the scalar sector, we show that the full family of static, spherically symmetric and asymptotically flat solutions is obtained as the SL(2, ℝ ) orbit of the pure-dilaton FJNW solution, and we characterize the associated axion-dilaton charge space. We then analyze the perturbative regime of these solutions by comparing the onset of α ′ curvature corrections with that of string-loop corrections. Finally, we apply the string-black-hole correspondence criterion to the FJNW family by evaluating the local α ′ curvature diagnostic at the physical size R typ of a highly excited string state. With the normalization fixed on the Schwarzschild branch, Schwarzschild saturates the nominal α ′ threshold at the correspondence surface, whereas every scalar-haired FJNW branch lies above it. More generally, independently of the common overall normalization within the matching prescription, every nonzero-hair branch has a larger curvature diagnostic at the correspondence surface than Schwarzschild. Away from the correspondence point, scalar-haired exteriors may remain under α ′ control at sufficiently weak local self-gravity and may provide perturbatively controlled long-distance fields of highly excited string states whenever the local string coupling also remains weak.
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BibTeX
@article{pavone2026scalar,
title = {{Scalar hair at the string-black-hole correspondence}},
author = {E. Pavone},
journal = {Journal of High Energy Physics},
year = {2026},
month = oct,
doi = {10.1007/jhep10(2026)158},
url = {https://link.springer.com/article/10.1007/JHEP10(2026)158},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Scalar hair at the string-black-hole correspondence
AU - E. Pavone
PY - 2026
DA - 2026/10/14
JO - Journal of High Energy Physics
DO - 10.1007/jhep10(2026)158
UR - https://link.springer.com/article/10.1007/JHEP10(2026)158
AB - A bstract : We study static, spherically symmetric axion-dilaton solutions of the tree-level four-dimensional string effective action. Using the sigma-model structure of the scalar sector, we show that the full family of static, spherically symmetric and asymptotically flat solutions is obtained as the SL(2, ℝ ) orbit of the pure-dilaton FJNW solution, and we characterize the associated axion-dilaton charge space. We then analyze the perturbative regime of these solutions by comparing the onset of α ′ curvature corrections with that of string-loop corrections. Finally, we apply the string-black-hole correspondence criterion to the FJNW family by evaluating the local α ′ curvature diagnostic at the physical size R typ of a highly excited string state. With the normalization fixed on the Schwarzschild branch, Schwarzschild saturates the nominal α ′ threshold at the correspondence surface, whereas every scalar-haired FJNW branch lies above it. More generally, independently of the common overall normalization within the matching prescription, every nonzero-hair branch has a larger curvature diagnostic at the correspondence surface than Schwarzschild. Away from the correspondence point, scalar-haired exteriors may remain under α ′ control at sufficiently weak local self-gravity and may provide perturbatively controlled long-distance fields of highly excited string states whenever the local string coupling also remains weak.
SN - 1029-8479
ER -