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A rotating charged black string solution in the low energy effective field theory describing five dimensional heterotic string theory is constructed. The solution is labelled by mass, electric charge, axion charge and angular momentum per…
We reconsider here the problem of finding the general 4D spherically symmetric, asymptotically flat and time-independent solutions to the lowest-order string equations in the $\ap$ expansion. Our construction includes earlier work, but…
The interaction of a cosmic string with a four-dimensional stationary black hole is considered. If a part of an infinitely long string passes close to a black hole it can be captured. The final stationary configurations of such captured…
The interaction of a cosmic string with a four-dimensional stationary black hole is considered. If a part of an infinitely long string passes close to a black hole it can be captured. The final stationary configurations of such captured…
We discuss the classical 2-dim. black-hole in the framework of the non-perturbative formulation (in terms of non-relativistic fermions) of c=1 string field theory. We identify an off-shell operator whose classical equation of motion is that…
We determine the $s$-waves contribution of a scalar field to the four dimensional effective action for arbitrary spherically symmetric external gravitational fields. The result is applied to $4d$-black holes and it is shown that the energy…
Recent progress on the complete set of solutions of two dimensional classical string theory in any curved spacetime is reviewed. When the curvature is smooth the string solutions are deformed folded string solutions as compared to flat…
Recently, by explicit calculations at orders $\alpha',\alpha'^2,\alpha'^3$, it has been observed that the effective action of string theory at the critical dimension is independent of the background for the closed spacetime manifolds. In…
We consider string inspired models in $D=10$ spacetime dimensions, which include couplings with 1- and 3-form fields as well as $R^4$ higher curvature corrections to the gravitational action. For such models, we explicitly construct a…
We study charged black hole solutions in Einstein-Maxwell-Gauss-Bonnet theory with the dilaton field which is the low-energy effective theory of the heterotic string. The spacetime is $D$-dimensional and assumed to be static and plane…
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 derive the quantum effective action and the respective quantum equations of motion from multi-graviton correlation functions in asymptotically safe quantum gravity. The fully momentum-dependent couplings of three- and four-graviton…
We study cosmological scenarios resulting from effective actions in four dimensions which are, under some assumptions, connected with multidimensional, supergravity and string theories. These effective actions are labeled by the parameters…
The first order corrections to the geometry of the (2+1)-dimensional black hole due to back-reaction of a massless conformal scalar field are computed. The renormalized stress energy tensor used as the source of Einstein equations is…
Charged massive scalar fields are considered in the gravitational and electromagnetic field produced by a dyonic black hole with a cosmic string along its axis of symmetry. Exact solutions of both angular and radial parts of the covariant…
We generalize the results of a previous paper by one of the authors to show a relationship among a class of string solutions through $O(\tilde d, \tilde d)$ transformations. The results are applied to a rotating black hole solution of three…
We find all the classical solutions (minimal surfaces) of open or closed strings in {\it any} two dimensional curved spacetime. As examples we consider the SL(2,R)/R two dimensional black hole, and any 4D black hole in the Schwarzschild…
We present numerical evidences for the existence of rotating black hole solutions in d-dimensional Einstein-Maxwell theory with a cosmological constant and for $d$ odd. The metric used possesses $(d+1)/2$ Killing vectors and the solutions…
We study the classical double copy for static black string solutions in an Anti--de Sitter (AdS) background. By casting the black string metric into Kerr--Schild form over a cylindrical AdS geometry, we construct the corresponding single…
We show that, given a classical solution of the heterotic string theory which is independent of $d$ of the space time directions, and for which the gauge field configuration lies in a subgroup that commutes with $p$ of the $U(1)$ generators…