The Dark Side of String Theory: Black Holes and Black Strings

This is a summary of a lecture I gave at the workshop on dynamics and thermodynamics of black holes and naked singularities at Politecnico Milano. It is directed to a non-expert audience and reviews several ways in which string theory accounts for black hole microstates. In particular, I give an elementary introduction to the correspondence principle by Horowitz/Polchinski, to the state counting for the three-charge black hole by Strominger and Vafa, and to the recent proposa...

In the first part of this talk, I consider some exact string solutions in curved spacetimes. In curved spacetimes with a Killing vector (timelike or spacelike), the string equations of motion and constraints are reduced to the Hamilton equations of a relativistic point-particle in a scalar potential, by imposing a particular ansatz. As special examples I consider circular strings in axially symmetric spacetimes, as well as stationary strings in stationary spacetimes. In the s...

This paper serves as an extended version of our previous letter arXiv:2212.03808 [hep-th]. In this paper, we investigate the non-perturbative and non-singular black hole solutions derived from complete $\alpha^{\prime}$ corrected Hohm-Zwiebach action in different gauges (coordinate systems). In addition to the results that we obtained in the previous letter, we present the following additional results in this paper: 1) The regular black hole solutions in different gauges can ...

We examine the two-dimensional spacetimes that emerge from string theory. We find all the solutions with no tachyons, and show that the only non-trivial solution is the black hole spacetime. We examine the role of duality in this picture. We then explore the thermodynamics of these solutions which is complicated by the fact that only in two spacetime dimensions is it impossible to redefine the dilaton field in terms of a canonical scalar field. Finally, we extend our analysis...

We construct open cosmic string solutions in Schwarzschild black hole and non-dilatonic black p-brane backgrounds. These strings can be thought to stretch between two D-branes or between a D-brane and the horizon in curved space-time. We study small fluctuations around these solutions and discuss their basic properties.

This thesis is devoted to the study of black hole solutions in ungauged four-dimensional extended Supergravity. We characterize the most general spherically symmetric and static black-hole solution of ungauged Supergravity, and use the result to study the hidden conformal symmetries of Supergravity black holes, obtaining the full Virasoro algebra of the dual conformal field theory. We obtain also all the supersymmetric black-hole metrics of all extended Supergravities using t...

In this work, a regular black string solution will be presented from the method used by Simpson-Visser to regularize the Schwarzschild solution. As in the Simpson-Visser work, in this new black string solution, it is possible to represent both a regular black hole and a wormhole just by changing the value of a parameter "$a$" used in its metric. Tensors and curvature invariants were analyzed to verify the regularity of the solution, as well as the energy conditions of the sys...

Two solutions of stringy gravity in three and four dimensions which admit interpretation as a black hole and a black string, respectively, are discussed. It is demonstrated that they are exact WZWN nonlinear sigma models to all orders in the inverse string tension, and hence represent exact conformal field theories on the world-sheet. Furthermore, since the dilaton for these two solutions is constant, they also solve the equations of motion of standard GR with a minimally cou...

Analytic solutions to low-energy string theory, which describe arbitrary numbers of extreme `black holes (strings)' in linear dilaton vacua, are found.

In this report a detailed derivation of the dynamical equations for an n dimensional heterotic string theory of the Horowitz type is carried out in the string frame and in the Einstein frame too. In particular, the dynamical equations of the three dimensional string theory are explicitly given. The relation of the Horowitz Welch and Horne Horowitz string black hole solution is exhibited. The Chan Mann charged dilaton solution is derived and the subclass of string solutions fi...