1,396 research outputs found

    Nernst branes from special geometry

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    We construct new black brane solutions in U(1)U(1) gauged N=2{\cal N}=2 supergravity with a general cubic prepotential, which have entropy density sT1/3s\sim T^{1/3} as T0T \rightarrow 0 and thus satisfy the Nernst Law. By using the real formulation of special geometry, we are able to obtain analytical solutions in closed form as functions of two parameters, the temperature TT and the chemical potential μ\mu. Our solutions interpolate between hyperscaling violating Lifshitz geometries with (z,θ)=(0,2)(z,\theta)=(0,2) at the horizon and (z,θ)=(1,1)(z,\theta)=(1,-1) at infinity. In the zero temperature limit, where the entropy density goes to zero, we recover the extremal Nernst branes of Barisch et al, and the parameters of the near horizon geometry change to (z,θ)=(3,1)(z,\theta)=(3,1).Comment: 37 pages. v2: numerical pre-factors of scalar fields q_A corrected in Section 3. No changes to conclusions. References adde

    The protist Trichomonas vaginalis harbors multiple lineages of transcriptionally active Mutator-like elements

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    <p>Abstract</p> <p>Background</p> <p>For three decades the <it>Mutator </it>system was thought to be exclusive of plants, until the first homolog representatives were characterized in fungi and in early-diverging amoebas earlier in this decade.</p> <p>Results</p> <p>Here, we describe and characterize four families of <it>Mutator</it>-like elements in a new eukaryotic group, the Parabasalids. These <b><it>T</it></b><it>richomonas </it><b><it>v</it></b><it>aginalis </it><it><b>Mu</b>tator- <b>l</b>ike </it><it><b>e</b>lements</it>, or <it>TvMULEs</it>, are active in <it>T. vaginalis </it>and patchily distributed among 12 trichomonad species and isolates. Despite their relatively distinctive amino acid composition, the inclusion of the repeats <it>TvMULE1</it>, <it>TvMULE2</it>, <it>TvMULE3 </it>and <it>TvMULE4 </it>into the <it>Mutator </it>superfamily is justified by sequence, structural and phylogenetic analyses. In addition, we identified three new <it>TvMULE</it>-related sequences in the genome sequence of <it>Candida albicans</it>. While <it>TvMULE1 </it>is a member of the <it>MuDR </it>clade, predominantly from plants, the other three <it>TvMULEs</it>, together with the <it>C. albicans </it>elements, represent a new and quite distinct <it>Mutator </it>lineage, which we named <it>TvCaMULEs</it>. The finding of <it>TvMULE1 </it>sequence inserted into other putative repeat suggests the occurrence a novel TE family not yet described.</p> <p>Conclusion</p> <p>These findings expand the taxonomic distribution and the range of functional motif of <it>MULEs </it>among eukaryotes. The characterization of the dynamics of <it>TvMULEs </it>and other transposons in this organism is of particular interest because it is atypical for an asexual species to have such an extreme level of TE activity; this genetic landscape makes an interesting case study for causes and consequences of such activity. Finally, the extreme repetitiveness of the <it>T. vaginalis </it>genome and the remarkable degree of sequence identity within its repeat families highlights this species as an ideal system to characterize new transposable elements.</p

    New supersymmetric higher-derivative couplings: Full N=2 superspace does not count!

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    An extended class of N=2 locally supersymmetric invariants with higher-derivative couplings based on full superspace integrals, is constructed. These invariants may depend on unrestricted chiral supermultiplets, on vector supermultiplets and on the Weyl supermultiplet. Supersymmetry is realized off-shell. A non-renormalization theorem is proven according to which none of these invariants can contribute to the entropy and electric charges of BPS black holes. Some of these invariants may be relevant for topological string deformations.Comment: 24 pages, v2: version published in JHEP, one reference added and typos corrected, v3: reference adde

    A Twist in the Dyon Partition Function

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    In four dimensional string theories with N=4 and N=8 supersymmetries one can often define twisted index in a subspace of the moduli space which captures additional information on the partition function than the ones contained in the usual helicity trace index. We compute several such indices in type IIB string theory on K3 x T^2 and T^6, and find that they share many properties with the usual helicity trace index that captures the spectrum of quarter BPS states in N=4 supersymmetric string theories. In particular the partition function is a modular form of a subgroup of Sp(2,Z) and the jumps across the walls of marginal stability are controlled by the residues at the poles of the partition function. However for large charges the logarithm of this index grows as 1/n times the entropy of a black hole carrying the same charges where n is the order of the symmetry generator that is used to define the twisted index. We provide a macroscopic explanation of this phenomenon using quantum entropy function formalism. The leading saddle point corresponding to the attractor geometry fails to contribute to the twisted index, but a Z_n orbifold of the attractor geometry produces the desired contribution.Comment: LaTeX file, 35 pages; v2: references adde

    Nernst branes in gauged supergravity

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    We study static black brane solutions in the context of N = 2 U(1) gauged supergravity in four dimensions. Using the formalism of first-order flow equations, we construct novel extremal black brane solutions including examples of Nernst branes, i.e. extremal black brane solutions with vanishing entropy density. We also discuss a class of non-extremal generalizations which is captured by the first-order formalism.Comment: 44 pages, 3 figures, v2: added appendix B and references, minor typographic changes, v3: added some clarifying remarks, version published in JHE

    Black holes in supergravity and integrability

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    Stationary black holes of massless supergravity theories are described by certain geodesic curves on the target space that is obtained after dimensional reduction over time. When the target space is a symmetric coset space we make use of the group-theoretical structure to prove that the second order geodesic equations are integrable in the sense of Liouville, by explicitly constructing the correct amount of Hamiltonians in involution. This implies that the Hamilton-Jacobi formalism can be applied, which proves that all such black hole solutions, including non-extremal solutions, possess a description in terms of a (fake) superpotential. Furthermore, we improve the existing integration method by the construction of a Lax integration algorithm that integrates the second order equations in one step instead of the usual two step procedure. We illustrate this technology with a specific example.Comment: 44 pages, small typos correcte

    Short-term efficacy of physical interventions in osteoarthritic knee pain. A systematic review and meta-analysis of randomised placebo-controlled trials.

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    BACKGROUND: Treatment efficacy of physical agents in osteoarthritis of the knee (OAK) pain has been largely unknown, and this systematic review was aimed at assessing their short-term efficacies for pain relief. METHODS: Systematic review with meta-analysis of efficacy within 1-4 weeks and at follow up at 1-12 weeks after the end of treatment. RESULTS: 36 randomised placebo-controlled trials (RCTs) were identified with 2434 patients where 1391 patients received active treatment. 33 trials satisfied three or more out of five methodological criteria (Jadad scale). The patient sample had a mean age of 65.1 years and mean baseline pain of 62.9 mm on a 100 mm visual analogue scale (VAS). Within 4 weeks of the commencement of treatment manual acupuncture, static magnets and ultrasound therapies did not offer statistically significant short-term pain relief over placebo. Pulsed electromagnetic fields offered a small reduction in pain of 6.9 mm [95% CI: 2.2 to 11.6] (n = 487). Transcutaneous electrical nerve stimulation (TENS, including interferential currents), electro-acupuncture (EA) and low level laser therapy (LLLT) offered clinically relevant pain relieving effects of 18.8 mm [95% CI: 9.6 to 28.1] (n = 414), 21.9 mm [95% CI: 17.3 to 26.5] (n = 73) and 17.7 mm [95% CI: 8.1 to 27.3] (n = 343) on VAS respectively versus placebo control. In a subgroup analysis of trials with assumed optimal doses, short-term efficacy increased to 22.2 mm [95% CI: 18.1 to 26.3] for TENS, and 24.2 mm [95% CI: 17.3 to 31.3] for LLLT on VAS. Follow-up data up to 12 weeks were sparse, but positive effects seemed to persist for at least 4 weeks after the course of LLLT, EA and TENS treatment was stopped. CONCLUSION: TENS, EA and LLLT administered with optimal doses in an intensive 2-4 week treatment regimen, seem to offer clinically relevant short-term pain relief for OAK
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