C. S. Shahbazi

Non-extremal black holes of N = 2, d = 4 supergravity

We propose a generic recipe for deforming extremal black holes into non-extremal black holes and we use it to find and study the static non-extremal black-hole solutions of several N = 2, d = 4 supergravity models

Dirac-Born-Infeld-Volkov-Akulov and deformation of supersymmetry

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H-FGK formalism for black-hole solutions of N=2, d=4 and d=5 supergravity

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Black holes and black strings of N = 2, d = 5 supergravity in the H-FGK formalism

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Black-hole solutions of N = 2, d = 4 supergravity with a quantum correction, in the H-FGK formalism

and STU with four charges). In all the cases considered, the non-extremal family of solutions smoothly interpolates between all the different extremal limits, supersymmetric and not supersymmetric. This fact can be used to explicitly find extremal non-supersymmetric solutions also in the cases in which the attractor mechanism does not completely fix the values of the scalars on the event horizon and they still depend on the boundary conditions at spatial infinity.We compare (supersymmetry) Bogomol’nyi bounds with extremality bounds, we find the first-order flow equations for the non-extremal solutions and the corresponding super-potential, which gives in the different extremal limits different superpotentials for extremal black holes. We also compute the entropies (areas) of the inner (Cauchy) and outer (event) horizons, finding in all cases that their product gives the square of the moduli-independent entropy of the extremal solution with the same electric and magnetic charges.

The FGK formalism for black p-branes in d dimensions

A bstractWe deform the action and the supersymmetry transformations of the d = 10 and d = 4 Maxwell supermultiplets so that at each order of the deformation the theory has 16 Maxwell multiplet deformed supersymmetries as well as 16 Volkov-Akulov type non-linear supersymmetries. The result agrees with the expansion in the string tension of the explicit action of the Dirac-Born-Infeld model and its supersymmetries, extracted from D9 and D3 superbranes, respectively. The half-maximal Dirac-Born-Infeld models with 8 Maxwell supermultiplet deformed supersymmetries and 8 Volkov-Akulov type supersymmetries are described by a new class of d = 6 vector branes related to chiral (2,0) supergravity, which we denote as ‘Vp-branes’. We use a space-filling V5 superbrane for the d = 6 model and a V3 superbrane for the d = 4 half-maximal Dirac-Born-Infeld (DBI) models. In this way we present a completion to all orders of the deformation of the Maxwell supermultiplets with maximal 16+16 supersymmetries in d = 10 and 4, and half-maximal 8+8 supersymmetries in d = 6 and 4.

Spin(7)-manifolds in compactifications to four dimensions

Abstract We rewrite the Ferrara–Gibbons–Kallosh (FGK) black-hole effective action of N = 2 , d = 4 , 5 supergravities coupled to vector multiplets, replacing the metric warp factor and the physical scalars with real variables that transform in the same way as the charges under duality transformations, which simplifies the equations of motion. For a given model, the form of the solution in these variables is the same for all spherically symmetric black holes, regardless of supersymmetry or extremality.

The tensor hierarchies of pure N = 2, d = 4, 5, 6 supergravities

A bstractWe study general classes and properties of extremal and non-extremal static black-hole solutions of N = 2, d = 5 supergravity coupled to vector multiplets using the recently proposed H-FGK formalism, which we also extend to static black strings. We explain how to determine the integration constants and physical parameters of the blackhole and black-string solutions. We derive some model-independent statements, including the transformation of non-extremal flow equations to the form of those for the extremal flow. We apply our methods to the construction of example solutions (among others a new extremal string solution of heterotic string theory on K3 × S1). In the cases where we have calculated it explicitly, the product of areas of the inner and outer horizon of a non-extremal solution coincides with the square of the moduli-independent area of the horizon of the extremal solution with the same charges.

Non-perturbative black holes in Type-IIA String Theory versus the No-Hair conjecture

A bstractWe apply the H-FGK formalism to the study of some properties of a general class of black holes in N = 2 supergravity in four dimensions that correspond to the harmonic and hyperbolic ansätze and we obtain explicit extremal and non-extremal solutions for the t3 model with and without a quantum correction. Not all solutions of the corrected model (quantum black holes), including in particular a solution with a single q1 charge, have a regular classical limit.

A Note on the hidden conformal structure of non-extremal black holes

A bstractWe present a generalization to an arbitrary number of spacetime (d) and world-volume (p + 1) dimensions of the formalism proposed by Ferrara, Gibbons and Kallosh to study black holes (p = 0) in d = 4 dimensions. We include the special cases in which there can be dyonic and self- or anti-self-dual black branes. Most of the results valid for 4-dimensional black holes (relations between temperature, entropy and non-extremality parameter, and between entropy and black-hole potential on the horizon) are straightforwardly generalized.We apply the formalism to the case of black strings in N = 2, d = 5 supergravity coupled to vector multiplets, in which the black-string potential can be expressed in terms of the dual central charge and work out an explicit example with one vector multiplet, determining supersymmetric and non-supersymmetric attractors and constructing the nonextremal black-string solutions that interpolate between them.