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BPS fivebrane stars. Part I. Expectation values of observables

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Zigdon, Yoav 


jats:titleAjats:scbstract</jats:sc> </jats:title>jats:pWe study ensembles of 1/2-BPS bound states of fundamental strings and NS-fivebranes (NS5-F1 states) in the AdS decoupling limit. We revisit a solution corresponding to an ensemble average of these bound states, and find that the appropriate duality frame for describing the near-source structure is the T-dual NS5-P frame, where the bound state is a collection of momentum waves on the fivebranes. We find that the fivebranes are generically well-separated; this property results in the applicability of perturbative string theory. The geometry sourced by the typical microstate is not close to that of an extremal non-rotating black hole; instead the fivebranes occupy a ball whose radius is parametrically much larger than the “stretched horizon” scale of the corresponding black hole. These microstates are thus better characterized as BPS fivebrane stars than as small black holes.</jats:p>jats:pWhen members of the ensemble spin with two fixed angular potentials about two orthogonal planes, we find that the spherical ball of the non-rotating ensemble average geometry deforms into an ellipsoid. This contrasts with ring structures obtained when fixing the angular momenta instead of the angular potentials; we trace this difference of ensembles to large fluctuations of the angular momentum in the ensemble of fixed angular potential.</jats:p>


Acknowledgements: We thank Nadav Drukker, Harvey Reall and Arkady Tseytlin for discussions. YZ thanks the Perimeter Institute and the organizers of Strings 2023 for their hospitality and the opportunity to present results written in this work. The research of YZ is supported by the Blavatnik fellowship, and was supported by the Adams fellowship and the German Research Foundation through a German-Israeli Project Cooperation (DIP) grant “Holography and the Swampland”. The work of EJM is supported in part by DOE grant DE-SC0009924.


4902 Mathematical Physics, 5107 Particle and High Energy Physics, 49 Mathematical Sciences, 51 Physical Sciences

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Journal of High Energy Physics

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