# School of Physics

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Research Content for the School of Physics. Researchers in the School of the Physics.

For queries regarding content of Faculty of Science please contact Salome Potgieter by email : salome.potgieter@wits.ac.za or Tel : 011 717 1961

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### Browsing School of Physics by Keyword "Black Holes"

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Item The hot attractor mechanism: decoupling without deep throats(Springer Verlag, 2016-04) Goldstein, K.; Jejjala, V.; Nampuri, S.Non-extremal black holes in (Formula presented.) supergravity have two horizons, the geometric mean of whose areas recovers the horizon area of the extremal black hole obtained from taking a smooth zero temperature limit. In prior work [1] using the attractor mechanism, we deduced the existence of several moduli independent invariant quantities obtained from averaging over a decoupled inter-horizon region. We establish that non-extremal geometries at the Reissner-Nordström point, where the scalar moduli are held fixed, can be lifted to solutions in supergravity with a near-horizon AdS3×S2. These solutions have the same entropy and temperature as the original black hole and therefore allow an interpretation of the underlying gravitational degrees of freedom in terms of CFT2. Symmetries of the moduli space enable us to explicate the origin of entropy in the extremal limit.Item Indefinite theta functions for counting attractor backgrounds(Springer, 2014-10-03) Cardoso, Gabriel Lopes; Ciraficia, Michele; Nampurib, SureshIn this note, we employ indefinite theta functions to regularize canonical partition functions for single-center dyonic BPS black holes. These partition functions count dyonic degeneracies in the Hilbert space of four-dimensional toroidally compactified heterotic string theory, graded by electric and magnetic charges. The regularization is achieved by viewing the weighted sums of degeneracies as sums over charge excitations in the near-horizon attractor geometry of an arbitrarily chosen black hole background, and eliminating the unstable modes. This enables us to rewrite these sums in terms of indefinite theta functions. Background independence is then implemented by using the transformation property of indefinite theta functions under elliptic transformations, while modular transformations are used to make contact with semi-classical results in supergravity.