1,381 research outputs found

    On Special Re-quantization of a Black Hole

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    Quantized expressions for the gravitational energy and momentum are derived from a linearized theory of teleparallel gravity. The derivation relies on a second-quantization procedure that constructs annihilation and creation operators for the graviton. The resulting gravitational field is a collection of gravitons, each of which has precise energy and momentum. On the basis of the weak-field approximation of Schwarzschild's solution, a new form for the quantization of the mass of a black hole is derived.Comment: 4 page

    Comprehensive medication reviews by ward-based pharmacists in Swedish hospitals: what does the patient have to say?

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    Rationale, aims, and objectives: Inappropriate medication prescribing and use amongst older patients is a major patient safety and health care problem. To promote appropriate medication prescribing and use, comprehensive medication reviews (CMRs) by ward-based pharmacists, including follow-up telephone calls after hospital discharge, have been conducted in older patients in the context of a randomized controlled trial (RCT). One of the key actors in a CMR is the patient. To support the understanding of the effects of CMRs on patients' health outcomes and improve clinical practice, knowledge about the patient perspective is needed. We therefore aimed to explore older patients' experiences with, and views on, hospital-initiated CMRs and follow-up telephone calls by ward-based clinical pharmacists within an RCT. Methods: We conducted in-depth semi-structured interviews with 15 patients (66-94 years) and carers from four hospitals in Sweden. Discussion topics included communication, information, decision-making, and effects on the patient. Interviews took place after discharge, were audio-recorded, transcribed verbatim, and thematically analysed using a framework approach. Results: In general, patients' experiences and views were positive. Seven key themes were identified: (a) feeling of being taken care of and heterogenous health effects; (b) the pharmacist is competent; (c) despite the unclear role of pharmacists, their involvement is appreciated; (d) patients rely on health care professionals for decision-making; (e) importance of being informed, but receiving and retaining information is problematic; (f) time, location, and other factors influencing the effectiveness of CMRs; and (g) generic substitution is a problem. Conclusions: Older patients generally have positive experiences with and views on CMRs and follow-up telephone calls. However, some factors, like the unclear role of the ward-based pharmacist and problems with receiving and retaining information, may negatively impact the effectiveness of these interventions. Future initiatives on hospital-initiated CMRs by clinical pharmacists should address these negative factors and utilize the positive views

    Proof Relevant Corecursive Resolution

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    Resolution lies at the foundation of both logic programming and type class context reduction in functional languages. Terminating derivations by resolution have well-defined inductive meaning, whereas some non-terminating derivations can be understood coinductively. Cycle detection is a popular method to capture a small subset of such derivations. We show that in fact cycle detection is a restricted form of coinductive proof, in which the atomic formula forming the cycle plays the role of coinductive hypothesis. This paper introduces a heuristic method for obtaining richer coinductive hypotheses in the form of Horn formulas. Our approach subsumes cycle detection and gives coinductive meaning to a larger class of derivations. For this purpose we extend resolution with Horn formula resolvents and corecursive evidence generation. We illustrate our method on non-terminating type class resolution problems.Comment: 23 pages, with appendices in FLOPS 201

    Conformal Symmetry of a Black Hole as a Scaling Limit: A Black Hole in an Asymptotically Conical Box

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    We show that the previously obtained subtracted geometry of four-dimensional asymptotically flat multi-charged rotating black holes, whose massless wave equation exhibit SL(2,R)×SL(2,R)×SO(3)SL(2,\R) \times SL(2,\R) \times SO(3) symmetry may be obtained by a suitable scaling limit of certain asymptotically flat multi-charged rotating black holes, which is reminiscent of near-extreme black holes in the dilute gas approximation. The co-homogeneity-two geometry is supported by a dilation field and two (electric) gauge-field strengths. We also point out that these subtracted geometries can be obtained as a particular Harrison transformation of the original black holes. Furthermore the subtracted metrics are asymptotically conical (AC), like global monopoles, thus describing "a black hole in an AC box". Finally we account for the the emergence of the SL(2,R)×SL(2,R)×SO(3)SL(2,\R) \times SL(2,\R) \times SO(3) symmetry as a consequence of the subtracted metrics being Kaluza-Klein type quotients of AdS3×4S3 AdS_3\times 4 S^3. We demonstrate that similar properties hold for five-dimensional black holes.Comment: Sections 3 and 4 significantly augmente

    Phase structure of black branes in grand canonical ensemble

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    This is a companion paper of our previous work [1] where we studied the thermodynamics and phase structure of asymptotically flat black pp-branes in a cavity in arbitrary dimensions DD in a canonical ensemble. In this work we study the thermodynamics and phase structure of the same in a grand canonical ensemble. Since the boundary data in two cases are different (for the grand canonical ensemble boundary potential is fixed instead of the charge as in canonical ensemble) the stability analysis and the phase structure in the two cases are quite different. In particular, we find that there exists an analog of one-variable analysis as in canonical ensemble, which gives the same stability condition as the rather complicated known (but generalized from black holes to the present case) two-variable analysis. When certain condition for the fixed potential is satisfied, the phase structure of charged black pp-branes is in some sense similar to that of the zero charge black pp-branes in canonical ensemble up to a certain temperature. The new feature in the present case is that above this temperature, unlike the zero-charge case, the stable brane phase no longer exists and `hot flat space' is the stable phase here. In the grand canonical ensemble there is an analog of Hawking-Page transition, even for the charged black pp-brane, as opposed to the canonical ensemble. Our study applies to non-dilatonic as well as dilatonic black pp-branes in DD space-time dimensions.Comment: 32 pages, 2 figures, various points refined, discussion expanded, references updated, typos corrected, published in JHEP 1105:091,201

    Thermodynamical Metrics and Black Hole Phase Transitions

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    An important phase transition in black hole thermodynamics is associated with the divergence of the specific heat with fixed charge and angular momenta, yet one can demonstrate that neither Ruppeiner's entropy metric nor Weinhold's energy metric reveals this phase transition. In this paper, we introduce a new thermodynamical metric based on the Hessian matrix of several free energy. We demonstrate, by studying various charged and rotating black holes, that the divergence of the specific heat corresponds to the curvature singularity of this new metric. We further investigate metrics on all thermodynamical potentials generated by Legendre transformations and study correspondences between curvature singularities and phase transition signals. We show in general that for a system with n-pairs of intensive/extensive variables, all thermodynamical potential metrics can be embedded into a flat (n,n)-dimensional space. We also generalize the Ruppeiner metrics and they are all conformal to the metrics constructed from the relevant thermodynamical potentials.Comment: Latex, 25 pages, reference added, typos corrected, English polished and the Hawking-Page phase transition clarified; to appear in JHE

    Phase transitions and critical behavior of black branes in canonical ensemble

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    We study the thermodynamics and phase structure of asymptotically flat non-dilatonic as well as dilatonic black branes in a cavity in arbitrary dimensions (DD). We consider the canonical ensemble and so the charge inside the cavity and the temperature at the wall are fixed. We analyze the stability of the black brane equilibrium states and derive the phase structures. For the zero charge case we find an analog of Hawking-Page phase transition for these black branes in arbitrary dimensions. When the charge is non-zero, we find that below a critical value of the charge, the phase diagram has a line of first-order phase transition in a certain range of temperatures which ends up at a second order phase transition point (critical point) as the charge attains the critical value. We calculate the critical exponents at that critical point. Although our discussion is mainly concerned with the non-dilatonic branes, we show how it easily carries over to the dilatonic branes as well.Comment: 37 pages, 6 figures, the validity of using the effective action discussed, references adde

    Fast cavity-enhanced atom detection with low noise and high fidelity

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    Cavity quantum electrodynamics describes the fundamental interactions between light and matter, and how they can be controlled by shaping the local environment. For example, optical microcavities allow high-efficiency detection and manipulation of single atoms. In this regime fluctuations of atom number are on the order of the mean number, which can lead to signal fluctuations in excess of the noise on the incident probe field. Conversely, we demonstrate that nonlinearities and multi-atom statistics can together serve to suppress the effects of atomic fluctuations when making local density measurements on clouds of cold atoms. We measure atom densities below 1 per cavity mode volume near the photon shot-noise limit. This is in direct contrast to previous experiments where fluctuations in atom number contribute significantly to the noise. Atom detection is shown to be fast and efficient, reaching fidelities in excess of 97% after 10 us and 99.9% after 30 us.Comment: 7 pages, 4 figures, 1 table; extensive changes to format and discussion according to referee comments; published in Nature Communications with open acces

    Modelling survival and allele complementation in the evolution of genomes with polymorphic loci

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    We have simulated the evolution of sexually reproducing populations composed of individuals represented by diploid genomes. A series of eight bits formed an allele occupying one of 128 loci of one haploid genome (chromosome). The environment required a specific activity of each locus, this being the sum of the activities of both alleles located at the corresponding loci on two chromosomes. This activity is represented by the number of bits set to zero. In a constant environment the best fitted individuals were homozygous with alleles’ activities corresponding to half of the environment requirement for a locus (in diploid genome two alleles at corresponding loci produced a proper activity). Changing the environment under a relatively low recombination rate promotes generation of more polymorphic alleles. In the heterozygous loci, alleles of different activities complement each other fulfilling the environment requirements. Nevertheless, the genetic pool of populations evolves in the direction of a very restricted number of complementing haplotypes and a fast changing environment kills the population. If simulations start with all loci heterozygous, they stay heterozygous for a long time

    Boundary Terms and Junction Conditions for Generalized Scalar-Tensor Theories

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    We compute the boundary terms and junction conditions for Horndeski's panoptic class of scalar-tensor theories, and write the bulk and boundary equations of motion in explicitly second order form. We consider a number of special subclasses, including galileon theories, and present the corresponding formulae. Our analysis opens up of the possibility of studying tunnelling between vacua in generalized scalar-tensor theories, and braneworld dynamics. The latter follows because our results are independent of spacetime dimension.Comment: 13 pages, Equation corrected. Thanks to Tsutomu Kobayashi for informing us of the typ
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