Related papers: String Theory in a Pinch: Resolving the Gregory-La…
This thesis is almost entirely devoted to studying string theory backgrounds characterized by simple geometrical and integrability properties. The archetype of this type of system is given by Wess-Zumino-Witten models, describing string…
Three-dimensional Einstein gravity coupled to zero, one and two forms is solved in terms of a polyhomogeneous asymptotic expansion, generalising stationary black string solutions. From first order terms we obtain, in closed form, a new…
String theory in Euclidean flat space with a spacelike linear dilaton contains a D1-brane which looks like a semi-infinite hairpin. In addition to its curved shape, this ``hairpin brane'' has a condensate of the open string tachyon…
We solve the eigenvalue problem of general relativity for the case of charged black holes in two-dimensional heterotic string theory, derived by McGuigan et al. For the case of $m^{2}>q^{2}$, we find a physically acceptable time-dependent…
Metastable cosmic strings provide a minimal and predictive origin for the stochastic gravitational-wave background reported by Pulsar Timing Array experiments. We analyse this possibility in electroweak-like dark sectors with a single-stage…
We raise a thermodynamic puzzle for Horowitz--Polchinski (HP) solutions in the presence of extra compact dimensions and show that it can be resolved by the existence of higher-dimensional string stars. We provide non-trivial evidence for…
We develop the perturbation theory for R^2 string-corrected black hole solutions in d dimensions. After having obtained the master equation and the alpha'-corrected potential under tensorial perturbations of the metric, we study the…
This is a broad-brush review of how string theory addresses several important questions of gravitational physics. The problem of non-renormalizability is first reviewed, followed by introduction of string theory as an ultraviolet-finite…
In this paper we extend the analysis of the stability of an homogeneous black string in the presence of a negative cosmological constant with minimally coupled scalar fields. We recall the linear stability of this solutions under generic…
We compare the logarithm of the degeneracy of BPS saturated elementary string states and the string modified Bekenstein-Hawking entropy of the corresponding black holes in N=2 supersymmetric heterotic string compactification to four…
In this review I discuss various aspects of some of the recently constructed black hole and soliton solutions in string theory. I begin with the axionic instanton and related solutions of bosonic and heterotic string theory. The latter…
Similar to the superradiant effect in Reissner-Nordstr\"{o}m black hole, a charged scalar field can be amplified when impinging on the charged black hole in string theory. According to the black-hole bomb mechanism,the mass term of the…
We explore via linearized perturbation theory the Gregory-Laflamme instability of the NUT string (i.e the D=4 Lorentzian NUT solution uplifted to five dimensions). Our results indicate that the Gregory-Laflamme instability persists in the…
In this paper, a direct rigorous mathematical proof of the Gregory-Laflamme instability for the five-dimensional Schwarzschild black string is presented. Under a choice of ansatz for the perturbation and a gauge choice, the linearised…
Some issues on the stability of black string or brane solutions are summarized briefly. The stability of dS/AdS-Schwarzschild black strings has been investigated. Interestingly, the AdS-Schwarzschild black strings turn out to be stable as…
In this letter, we derive the singular condition for black holes and demonstrate the potential resolution of the Schwarzschild black hole singularity in general relativity using non-perturbative $\alpha^{\prime}$ corrections of string…
In this paper we study black string solutions considering the Lifshitz anisotropic scaling. We have shown that a new class of asymptotically Lifshitz solutions can be generated by an Einstein-Maxwell-Dilaton theory with a cosmological…
We review recent developments in understanding quantum/string corrections to BPS black holes and strings in five-dimensional supergravity. These objects are solutions to the effective action obtained from M-theory compactified on a…
We introduce a notion of quantum hair which completely characterizes the state of a D-brane in perturbative string theory. The hair manifests itself as a phase (more generally a unitary matrix in subspaces of degenerate string eigenstates)…
We demonstrate that string consistency in four spacetime dimensions leads to a spectrum of string states which satisfies the supertrace constraints Str(M^0)=0 and Str(M^2)=\Lambda at tree level, where \Lambda is the one-loop string…