Black hole microstates from branes at angle

We derive the leading g_s perturbation of the SUGRA fields generated by a supersymmetric configuration of respectively 1, 2 or 4 D3-branes intersecting at an arbitrary angle via the computation of the string theory disk scattering amplitude of one massless NSNS field interacting with open strings stretched between the branes. The configuration with four branes is expected to be relevant for black hole microstate counting in four dimensions.Comment: 28 pages, 1 figur

Pairing and condensation in a resonant Bose-Fermi mixture

We study by diagrammatic methods a mixture of single-component bosons and fermions, with boson-fermion coupling tuned by a Fano-Feshbach resonance. For increasing coupling, the growing boson-fermion pairing correlations progressively reduce the boson condensation temperature and make it eventually vanish at a critical coupling. Such quantum critical point depends very weakly on the population imbalance and for vanishing boson densities coincides with that found for the polaron-molecule transition in a strongly imbalanced Fermi gas, thus bridging two quite distinct physical systems.Comment: 4 pages, 4 figure

γ\gamma-ray flux from Dark Matter Annihilation in Galactic Caustics

In the frame of indirect dark matter searches we investigate the flux of high-energy $\gamma$-ray photons produced by annihilation of dark matter in caustics within our Galaxy under the hypothesis that the bulk of dark matter is composed of the lightest supersymmetric particles. Unfortunately, the detection of the caustics annihilation signal with currently available instruments is rather challenging. Indeed, with realistic assumptions concerning particle physics and cosmology, the $\gamma$-ray signal from caustics is below the detection threshold of both $\check {\rm C}$erenkov telescopes and satellite-borne experiments. Nevertheless, we find that this signal is more prominent than that expected if annihilation only occurs in the smoothed Galactic halo, with the possible exception of a $\sim 15^{\circ}$ circle around the Galactic center if the mass density profile of our Galaxy exhibits a sharp cusp there. We show that the angular distribution of this $\gamma$-ray flux changes significantly if DM annihilation preferentially occurs within virialized sub-halos populating our Galaxy rather than in caustics.Comment: 17 pages, 8 figures. Accepted for publication in JCA

On the detectability of gamma-rays from Dark Matter annihilation in the Local Group with ground-based experiments

Recent studies have suggested the possibility that the lightest supersymmetric particle is a suitable dark matter candidate. In this theoretical framework, annihilations in high density environments like the center of dark matter haloes may produce an intense flux of gamma-rays. In this paper we discuss the possibility of detecting the signatures of neutralino annihilation in nearby galaxies with next generation ground-based detectors.Comment: to appear in Proceedings of ICRC 200

The Impact of Vertical Integration and Outsourcing on Firm Efficiency: Evidence from the Italian Machine Tool Industry

In this paper we made use of an econometric approach to efficiency analysis in order to capture the role of vertical integration and outsourcing on firm's efficiency. Vertical integration is considered an indicator of structure, while outsourcing represents the process of its change. We consider inefficiency measures as indicators of organizational heterogeneity, related to the firm's choices regarding the phases of the production process that are under its control. We find support for the hypothesis of a relationship between vertical integration and efficiency. The results on outsourcing activity, and in particular the interaction between outsourcing and vertical structure, indicate that heterogeneous patterns, far from tending to cancel out each other as a consequence of common external changes, are reinforcing. Moreover, the sensitivity of inefficiency variance to the cycle, indicate that different firms may have different dynamic properties

Feedback and its Feedback Effect on Feedback: Photoionization Suppression and its Impact on Galactic Outflows

We show that radiative feedback due to reionization has a pronounced effect on the extent of mechanical feedback due to galactic outflows. The photoionization of the Intergalactic Medium (IGM) suppresses low-mass galaxy formation by photoheating the gas and limiting atomic line cooling. The number of low-mass galaxies is central for the enrichment of the IGM as these objects have the capacity to enrich a significant fraction (by volume) of the Universe. We use a modified version of our galactic outflow model, combined with a simple criterion for suppression, to investigate the potential impact upon the IGM. We find that this suppression strongly reduces the enrichment of the IGM and is sensitive to the reionization history. We also investigate the contribution of halos of different masses with varying degrees of suppression.Comment: 4 pages, 3 figures, class file included, accepted by ApJ Letters, minor changes and expanded Figure

Reduced-Order Modelling of the Bending of an Array of Torsional Micromirrors

Reduced-Order Modelling of the Bending of an Array of An array of micromirrors for beam steering optical switching has been designed in a thick polysilicon technology. A novel semi-analytical method to calculate the static characteristics of the micromirrors by taking into account the flexural deformation of the structure is presented. The results are compared with 3D coupled-field FEM simulation.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Vertical Integration and Efficiency: an application to the Italian Machine Tool Industry.

This paper analyzes the relationship between firm efficiency and vertical integration in the Italian machine tool (MT) industry. A theoretical model of entry and competition within an industry has been set up. In this model firms can choose either to be vertically integrated or not: the most efficientfirms self-select in being vertically integrated, while less efficientfirms prefer a disintegrated structure and they both coexist in equilibrium. In the second part of the paper the relationship between efficiency and vertical integration has been tested using a stochastic frontier framework in an novel panel dataset including around 500 MT builders. The theoretical prediction is confirmed: outsourcing seems a rational choice for less efficient firms to make positive operating profits and stay in the market; on the other hand, more efficient firms exploit their efficiency advantage to control a greater part of the production chain, possibly benefiting from greater coordination among different phases and tailored intermediate inputs.vertical integration; technical efficiency; firm heterogeneity; heteroskedastic frontier model