514 research outputs found

    Universal properties of the near-horizon optical geometry

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    We make use of the fact that the optical geometry near a static non-degenerate Killing horizon is asymptotically hyperbolic to investigate universal features of black hole physics. We show how the Gauss-Bonnet theorem allows certain lensing scenarios to be ruled in or out. We find rates for the loss of scalar, vector and fermionic `hair' as objects fall quasi- statically towards the horizon. In the process we find the Lienard-Wiechert potential for hyperbolic space and calculate the force between electrons mediated by neutrinos, extending the flat space result of Feinberg and Sucher. We use the enhanced conformal symmetry of the Schwarzschild and Reissner-Nordstrom backgrounds to re-derive the electrostatic field due to a point charge in a simple fashion

    A Note on the Instability of Lorentzian Taub-NUT-Space

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    I show that there are no SU(2)-invariant (time-dependent) tensorial perturbations of Lorentzian Taub-NUT space. It follows that the spacetime is unstable at the linear level against generic perturbations. I speculate that this fact is responsible for so far unsuccessful attempts to define a sensible thermodynamics for NUT-charged spacetimes.Comment: 13 pages, no figure

    Simple generalizations of Anti-de Sitter space-time

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    We consider new cosmological solutions which generalize the cosmological patch of the Anti-de Sitter (AdS) space-time, allowing for fluids with equations of state such that w≠−1w\neq -1. We use them to derive the associated full manifolds. We find that these solutions can all be embedded in flat five-dimensional space-time with −−+++--+++ signature, revealing deformed hyperboloids. The topology and causal-structure of these spaces is therefore unchanged, and closed time-like curves are identified, before a covering space is considered. However the structure of Killing vector fields is entirely different and so we may expect a different structure of Killing horizons in these solutions.Comment: 6 Pages, 5 Figures, Corrections and additions made for publication in Journal of Classical and Quantum Gravit

    Electrodynamics of Abrikosov vortices: the Field Theoretical Formulation

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    Electrodynamic phenomena related to vortices in superconductors have been studied since their prediction by Abrikosov, and seem to hold no fundamental mysteries. However, most of the effects are treated separately, with no guiding principle. We demonstrate that the relativistic vortex worldsheet in spacetime is the object that naturally conveys all electric and magnetic information, for which we obtain simple and concise equations. Breaking Lorentz invariance leads to down-to-earth Abrikosov vortices, and special limits of these equations include for instance dynamic Meissner screening and the AC Josephson relation. On a deeper level, we explore the electrodynamics of two-form sources in the absence of electric monopoles, in which the electromagnetic field strength itself acquires the characteristics of a gauge field. This novel framework leaves room for unexpected surprises.Comment: LaTeX, 23 pages, 5 figure

    The Sensitivity of Harassment to Orbit: Mass Loss from Early-Type Dwarfs in Galaxy Clusters

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    We conduct a comprehensive numerical study of the orbital dependence of harassment on early-type dwarfs consisting of 168 different orbits within a realistic, Virgo-like cluster, varying in eccentricity and pericentre distance. We find harassment is only effective at stripping stars or truncating their stellar disks for orbits that enter deep into the cluster core. Comparing to the orbital distribution in cosmological simulations, we find that the majority of the orbits (more than three quarters) result in no stellar mass loss. We also study the effects on the radial profiles of the globular cluster systems of early-type dwarfs. We find these are significantly altered only if harassment is very strong. This suggests that perhaps most early-type dwarfs in clusters such as Virgo have not suffered any tidal stripping of stars or globular clusters due to harassment, as these components are safely embedded deep within their dark matter halo. We demonstrate that this result is actually consistent with an earlier study of harassment of dwarf galaxies, despite the apparent contradiction. Those few dwarf models that do suffer stellar stripping are found out to the virial radius of the cluster at redshift=0, which mixes them in with less strongly harassed galaxies. However when placed on phase-space diagrams, strongly harassed galaxies are found offset to lower velocities compared to weakly harassed galaxies. This remains true in a cosmological simulation, even when halos have a wide range of masses and concentrations. Thus phase-space diagrams may be a useful tool for determining the relative likelihood that galaxies have been strongly or weakly harassed.Comment: 17 pages, 13 figures, Accepted to MNRAS 8th September 201

    Stationary Metrics and Optical Zermelo-Randers-Finsler Geometry

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    We consider a triality between the Zermelo navigation problem, the geodesic flow on a Finslerian geometry of Randers type, and spacetimes in one dimension higher admitting a timelike conformal Killing vector field. From the latter viewpoint, the data of the Zermelo problem are encoded in a (conformally) Painleve-Gullstrand form of the spacetime metric, whereas the data of the Randers problem are encoded in a stationary generalisation of the usual optical metric. We discuss how the spacetime viewpoint gives a simple and physical perspective on various issues, including how Finsler geometries with constant flag curvature always map to conformally flat spacetimes and that the Finsler condition maps to either a causality condition or it breaks down at an ergo-surface in the spacetime picture. The gauge equivalence in this network of relations is considered as well as the connection to analogue models and the viewpoint of magnetic flows. We provide a variety of examples.Comment: 37 pages, 6 figure

    An analysis of patterns of distribution of buprenorphine in the United States using ARCOS, Medicaid, and Medicare databases

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    Opioid overdose remains a problem in the United States despite pharmacotherapies, such as buprenorphine, in the treatment of opioid use disorder. This study characterized changes in buprenorphine use. Using the Drug Enforcement Administration\u27s ARCOS, Medicaid, and Medicare claims databases, patterns in buprenorphine usage in the United States from 2018 to 2020 were analyzed by examining percentage changes in total grams distributed and changes in grams per 100 K people in year-to-year usage based on ZIP code and state levels. For ARCOS from 2018 to 2019 and 2019 to 2020, total buprenorphine distribution in grams increased by 16.2% and 12.6%, respectively. South Dakota showed the largest statewide percentage increase in both 2018–2019 (66.1%) and 2019–2020 (36.7%). From 2018 to 2019, the ZIP codes ND-577 (156.4%) and VA-222 (−82.1%) had the largest and smallest percentage changes, respectively. From 2019 to 2020, CA-932 (250.2%) and IL-603 (−36.8%) were the largest and smallest, respectively. In both 2018–2019 and 2019–2020, PA-191 had the second highest increase in grams per 100K while OH-452 was the only ZIP code to remain in the top three largest decreases in grams per 100K in both periods. Among Medicaid patients in 2018, there was a nearly 2000-fold difference in prescriptions per 100k Medicaid enrollees between Kentucky (12 075) and Nebraska (6). Among Medicare enrollees in 2018, family medicine physicians and other primary care providers were the top buprenorphine prescribers. This study not only identified overall increases in buprenorphine availability but also pronounced state-level differences. Such geographic analysis can be used to discern which public policies and regional factors impact buprenorphine access
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