Adding new hair to the 3-charge black ring

Motivated by the string theory analysis of arXiv:1108.6331, we construct a class of 1/8-BPS solutions of type IIB supergravity compactified on S^1 x T^4. In this duality frame our ansatz allows for a non-trivial NS-NS B-field which has been usually set to zero in previous studies of 1/8-BPS geometries. We provide a M-theory description of these new geometries and show that they can be interpreted as the lift of solutions of the N=2 5D supergravity with three vector multiplets and whose scalar manifold is the symmetric space SO(1,1) x (SO(1,2)/SO(2)). Finally we show that the non-minimal 5D black rings provide an explicit example of solutions falling in this ansatz. In particular we point out the existence of a black ring that has an extra dipole charge with respect to the solutions of the STU-model. In the near-horizon limit, this ring has an AdS_3 x S^3 geometry with the same radius as the one of the 3-charge black hole and thus its microstates should belong to the usual D1-D5 CFT.Comment: 18 page

String derivation of two-loop Feynman diagrams

We briefly review the technology involved in extracting the field-theory limit of multiloop bosonic string amplitudes, and we apply it to the evaluation of simple two-loop diagrams involving scalars and gauge bosons.Comment: 7 pages, 1 figure, contributed to Beyond the Standard Model V, Balholm, Norway, April 1997. Latex with aipproc.st

Twisted determinants and bosonic open strings in an electromagnetic field

The bosonization equivalence between the 2-dimensional Dirac and Laplacian operators can be used to derive new interesting identities involving Theta functions. We use these formulae to compute the multiloop partition function of the bosonic open string in presence of a constant electromagnetic field.Comment: 7 pages; Contribution to the proceedings of the 36th International Symposium Ahrenshoop. v2: References adde

On the effective action of stable non-BPS branes

We study the world-volume effective action of stable non-BPS branes present in Type II theories compactified on K3. In particular, by exploiting the conformal description of these objects available in the orbifold limit, we argue that their world-volume effective theory can be chiral. The resulting anomalies are cancelled through the usual inflow mechanism provided there are anomalous couplings, similar to those of BPS branes, to the twisted R-R fields. We also show that this result is in agreement with the conjectured interpretation of these non-BPS configurations as BPS branes wrapped on non-supersymmetric cycles of the K3.Comment: 12 pages, LaTex, no figure

High-energy string-brane scattering: leading eikonal and beyond

We extend previous techniques for calculations of transplanckian-energy string-string collisions to the high-energy scattering of massless closed strings from a stack of N Dp-branes in Minkowski spacetime. We show that an effective non-trivial metric emerges from the string scattering amplitudes by comparing them against the semiclassical dynamics of high-energy strings in the extremal p-brane background. By changing the energy, impact parameter and effective open string coupling, we are able to explore various interesting regimes and to reproduce classical expectations, including tidal-force excitations, even beyond the leading-eikonal approximation.Comment: 40 pages, 5 figures, v2: minor corrections, new appendix with a discussion of the Feynman diagrams contributing to the scattering amplitude in the field theory limi

Entanglement entropy and D1-D5 geometries

http://dx.doi.org/10.1103/PhysRevD.90.066004Giusto, Stefano, and Rodolfo Russo. "Entanglement Entropy and D1-D5 geometries." Physical Review D 90.6 (2014): 066004

Stable non-BPS states in string theory: a pedagogical review

We present a pedagogical review of the stable non-BPS states in string theory which have recently attracted some attention in the literature. In particular, following the analysis of A. Sen, we discuss in detail the case of the stable non-BPS D-particle of Type I theory whose existence is predicted (and required) by the heterotic/Type I duality. We show that this D-particle originates from an unstable bound state formed by a D1/anti-D1 pair of Type IIB in which the tachyon field acquires a solitonic kink configuration. The mechanism of tachyon condensation is discussed first at a qualitative level and then with an exact conformal field theory analysis.Comment: 58 pages, 1 figure; minor correction

The gravitational eikonal: from particle, string and brane collisions to black-hole encounters

Motivated by conceptual problems in quantum theories of gravity, the gravitational eikonal approach, inspired by its electromagnetic predecessor, has been successfully applied to the transplanckian energy collisions of elementary particles and strings since the late eighties, and to string-brane collisions in the past decade. After the direct detection of gravitational waves from black-hole mergers, most of the attention has shifted towards adapting these methods to the physics of black-hole encounters. For such systems, the eikonal exponentiation provides an amplitude-based approach to calculate classical gravitational observables, thus complementing more traditional analytic methods such as the Post-Newtonian expansion, the worldline formalism, or the Effective-One-Body approach. In this review we summarize the main ideas and techniques behind the gravitational eikonal formalism. We discuss how it can be applied in various different physical setups involving particles, strings and branes and then we mainly concentrate on the most recent developments, focusing on massive scalars minimally coupled to gravity, for which we aim at being as self-contained and comprehensive as possible.Comment: 208 pages, 19 figure