The role of self-interacting right-handed neutrinos in galactic structure

It has been shown previously that the DM in galactic halos can be explained by a self-gravitating system of massive keV fermions (`inos') in thermodynamic equilibrium, and predicted the existence of a denser quantum core of inos towards the center of galaxies. In this article we show that the inclusion of self-interactions among the inos, modeled within a relativistic mean-field-theory approach, allows the quantum core to become massive and compact enough to explain the dynamics of the S-cluster stars closest to the Milky Way's galactic center. The application of this model to other galaxies such as large elliptical harboring massive central dark objects of $\sim 10^9 M_\odot$ is also investigated. We identify these interacting inos with sterile right-handed neutrinos pertaining to minimal extensions of the Standard Model, and calculate the corresponding total cross-section $\sigma$ within an electroweak-like formalism to be compared with other observationally inferred cross-section estimates. The coincidence of an ino mass range of few tens of keV derived here only from the galactic structure, with the range obtained independently from other astrophysical and cosmological constraints, points towards an important role of the right-handed neutrinos in the cosmic structure.Comment: 33 pages, 9 figures, version to appear in JCA

Viscoresistive MHD Configurations of Plasma in Accretion Disks

We present a discussion of two-dimensional magneto-hydrodynamics (MHD) configurations, concerning the equilibria of accretion disks of a strongly magnetized astrophysical object. We set up a viscoresistive scenario which generalizes previous two-dimensional analyses by reconciling the ideal MHD coupling of the vertical and the radial equilibria within the disk with the standard mechanism of the angular momentum transport, relying on dissipative properties of the plasma configuration. The linear features of the considered model are analytically developed and the non-linear configuration problem is addressed, by fixing the entire disk profile at the same order of approximation. Indeed, the azimuthal and electron force balance equations are no longer automatically satisfied when poloidal currents and matter fluxes are included in the problem. These additional components of the equilibrium configuration induce a different morphology of the magnetic flux surface, with respect to the ideal and simply rotating disk.Comment: 19 pages, 4 figures. To appear on the Proceedings of the Second Italian-Pakistani Workshop on Relativistic Astrophysic

Abundant stable gauge field hair for black holes in anti-de sitter space

We present new hairy black hole solutions of SU(N) Einstein-Yang-Mills (EYM) theory in asymptotically anti–de Sitter (AdS) space. These black holes are described by N+1 independent parameters and have N-1 independent gauge field degrees of freedom. Solutions in which all gauge field functions have no zeros exist for all N, and for a sufficiently large (and negative) cosmological constant. At least some of these solutions are shown to be stable under classical, linear, spherically symmetric perturbations. Therefore there is no upper bound on the amount of stable gauge field hair with which a black hole in AdS can be endowed

Thermalization of a nonequilibrium electron-positron-photon plasma

Starting from a nonequilibrium configuration we analyse the essential role of the direct and the inverse binary and triple interactions in reaching an asymptotic thermal equilibrium in a homogeneous isotropic electron-positron-photon plasma. We focus on energies in the range 0.1--10 MeV. We numerically integrate the integro-partial differential relativistic Boltzmann equation with the exact QED collisional integrals taking into account all binary and triple interactions in the plasma. We show that first, when detailed balance is reached for all binary interactions on a timescale $t_{k}\lesssim10^{-14}$sec, photons and electron-positron pairs establish kinetic equilibrium. Successively, when triple interactions fulfill the detailed balance on a timescale $t_{eq}\lesssim10^{-12}$sec, the plasma reaches thermal equilibrium. It is shown that neglecting the inverse triple interactions prevents reaching thermal equilibrium. Our results obtained in the theoretical physics domain also find application in astrophysics and cosmology.Comment: 4 pages, 3 figures, Phys. Rev. Lett., to appea

The use of video-assisted thoracic surgery in the management of Pancoast tumors

We describe our experience using video-assisted thoracic surgery (VATS) as an adjunct to the surgical management of Pancoast tumors. Between March 2004 and November 2009, 13 patients with Pancoast tumors were included in this study. Surgery was performed by positioning the patient to allow either an anterior or a posterior thoracotomy. VATS was employed to explore the pleural cavity, to optimize the surgical access and as an assistance during surgical resection. Three patients with pleural carcinosis at thoracoscopy did not undergo further surgery. Seven lobectomies and three wedge resections were performed with an en bloc chest-wall resection and mediastinal lymphadenectomy. The surgical approaches were a transmanubrial L-shaped incision (ns1), a posterior thoracotomy (ns8), and a combined transmanubrial and posterior thoracotomy (ns1) which were dictated by the thoracoscopic findings. The average operative time was 200 min (range: 185–280 min); the average blood loss was 325 ml (range: 250–1200 ml). The average hospitalization was nine days (range: 8–30 days). Our study indicates that VATS may be an effective and safe adjunct to standard surgical resection in patients with Pancoast tumors. It reduces the magnitude of surgery, either by sparing the patient a useless thoracotomy or, by optimizing the site of the thoracotomy. It may also have a significant educational role

Late-Time Tails in Gravitational Collapse of a Self-Interacting (Massive) Scalar-Field and Decay of a Self-Interacting Scalar Hair

We study analytically the initial value problem for a self-interacting (massive) scalar-field on a Reissner-Nordstr\"om spacetime. Following the no-hair theorem we examine the dynamical physical mechanism by which the self-interacting (SI) hair decays. We show that the intermediate asymptotic behaviour of SI perturbations is dominated by an oscillatory inverse power-law decaying tail. We show that at late-times the decay of a SI hair is slower than any power-law. We confirm our analytical results by numerical simulations.Comment: 16 pages, 3 ps figures, Revte

Nonlocal quantitative isoperimetric inequalities

We show a quantitative-type isoperimetric inequality for fractional perimeters where the deficit of the t-perimeter, up to multiplicative constants, controls from above that of the s-perimeter, with s smaller than t. To do this we consider a problem of independent interest: we characterize the volume-constrained minimizers of a nonlocal free energy given by the difference of the t-perimeter and the s-perimeter. In particular, we show that balls are the unique minimizers if the volume is sufficiently small, depending on t 12 s, while the existence vs. nonexistence of minimizers for large volumes remains open. We also consider the corresponding isoperimetric problem and prove existence and regularity of minimizers for all s, t. When s = 0 this problem reduces to the fractional isoperimetric problem, for which it is well known that balls are the only minimizers