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Search: authors:"Rodolfo Russo"

15 papers found.
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Infrared divergences and harmonic anomalies in the two-loop superstring effective action

We analyze the pertubative contributions to the \( {D}^4{\mathrm{\mathcal{R}}}^4 \) and \( {D}^6{\mathrm{\mathcal{R}}}^4 \) couplings in the low-energy effective action of type II string theory compactified on a torus T d , with particular emphasis on two-loop corrections. In general, it is necessary to introduce an infrared cut-off Λ to separate local interactions from non-local ...

Correlators at large c without information loss

We study a simple class of correlators with two heavy and two light operators both in the D1D5 CFT and in the dual AdS3 × S 3 × T 4 description. On the CFT side we focus on the free orbifold point and discuss how these correlators decompose in terms of conformal blocks, showing that they are determined by protected quantities. On the gravity side, the heavy states are described by ...

AdS3 holography for 1/4 and 1/8 BPS geometries

Recently a new class of 1/8-BPS regular geometries in type IIB string theory was constructed in arXiv:1503.01463. In this paper we provide a precise description of the semiclassical states dual, in the AdS/CFT sense, to these geometries. In explicit examples we show that the holographic 1-point functions and the Ryu-Takayanagi’s Entanglement Entropy for a single small interval ...

A microscopic description of absorption in high-energy string-brane collisions

We study the collision of a highly energetic light closed string off a stack of Dp-branes at (sub)string-scale impact parameters and in a regime justifying a perturbative treatment. Unlike at larger impact parameters — where elastic scattering and/or tidal excitations dominate — here absorption of the closed string by the brane system, with the associated excitation of open strings ...

Superdescendants of the D1D5 CFT and their dual 3-charge geometries

We describe how to obtain the gravity duals of semiclassical states in the D1-D5 CFT that are superdescendants of a class of RR ground states. On the gravity side, the configurations we construct are regular and asymptotically reproduce the 3-charge D1-D5-P black hole compactified on S 1 × T 4. The geometries depend trivially on the T 4 directions but non-trivially on the remaining ...

Two-loop Yang-Mills diagrams from superstring amplitudes

Starting from the superstring amplitude describing interactions among D-branes with a constant world-volume field strength, we present a detailed analysis of how the open string degeneration limits reproduce the corresponding field theory Feynman diagrams. A key ingredient in the string construction is represented by the twisted (Prym) super differentials, as their periods encode ...

Regge behavior saves string theory from causality violations

Higher-derivative corrections to the Einstein-Hilbert action are present in bosonic string theory leading to the potential causality violations recently pointed out by Camanho et al. [1]. We analyze in detail this question by considering high-energy string-brane collisions at impact parameters b ≤ l s (the string-length parameter) with l s ≫ R p (the characteristic scale of the ...

Matching the D 6ℛ4 interaction at two-loops

The coefficient of the D 6ℛ4 interaction in the low energy expansion of the two-loop four-graviton amplitude in type II superstring theory is known to be proportional to the integral of the Zhang-Kawazumi (ZK) invariant over the moduli space of genus-two Riemann surfaces. We demonstrate that the ZK invariant is an eigenfunction with eigenvalue 5 of the Laplace-Beltrami operator in ...

Habemus superstratum! A constructive proof of the existence of superstrata

We construct the first example of a superstratum: a class of smooth horizonless supergravity solutions that are parameterized by arbitrary continuous functions of (at least) two variables and have the same charges as the supersymmetric D1-D5-P black hole. We work in Type IIB string theory on T 4 or K3 and our solutions involve a subset of fields that can be described by a ...

Microscopic unitary description of tidal excitations in high-energy string-brane collisions

The eikonal operator was originally introduced to describe the effect of tidal excitations on higher-genus elastic string amplitudes at high energy. In this paper we provide a precise interpretation for this operator through the explicit tree-level calculation of generic inelastic transitions between closed strings as they scatter off a stack of parallel Dp-branes. We perform this ...

D1D5 microstate geometries from string amplitudes

We reproduce the asymptotic expansion of the D1D5 microstate geometries by computing the emission amplitudes of closed string states from disks with mixed D1D5 boundary conditions. Thus we provide a direct link between the supergravity and D-brane descriptions of the D1D5 microstates at non-zero string coupling. Microscopically, the profile functions characterizing the microstate ...

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 ...

Whole body bone scintigraphy in tenofovir-related osteomalacia: a case report

Introduction Tenofovir disoproxil fumarate (Viread®) is the only nucleotide reverse transcriptase inhibitor currently approved for the treatment of HIV. It is frequently prescribed not only for its efficacy but also for its decreased side effect profile compared with other nucleotide analogs. In addition, it is now increasingly recognized as a cause of acquired Fanconi's syndrome ...

TT virus infection in haemodialysis patients

Background. The recent discovery of a new parenterally transmitted DNA virus called TT virus (TTV) led us to investigate its prevalence in haemodialysis patients, a high‐risk group for blood‐borne infection, and to evaluate its role in liver disease. Moreover, we compared the TTV prevalence with the prevalence of other hepatitis virus coinfections. Methods. Serum samples of 78 ...

Transplantation - clinical II

Introduction and Aims: Endothelial progenitor cells (EPCs) participate in regenerative processes of the vasculature, develop incompetence in several states of disease, and also have prognostic value. The effects of various immunosuppressants on EPCs are unknown. Methods: In an open-label, randomized controlled trial cyclosporine A (CSA) treated kidney transplant recipients (KTRs) ...