7,815 research outputs found

    Density functional theory for strongly-correlated bosonic and fermionic ultracold dipolar and ionic gases

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    We introduce a density functional formalism to study the ground-state properties of strongly-correlated dipolar and ionic ultracold bosonic and fermionic gases, based on the self-consistent combination of the weak and the strong coupling limits. Contrary to conventional density functional approaches, our formalism does not require a previous calculation of the interacting homogeneous gas, and it is thus very suitable to treat systems with tunable long-range interactions. Due to its asymptotic exactness in the regime of strong correlation, the formalism works for systems in which standard mean-field theories fail.Comment: 5 pages, 2 figure

    Pair-distribution functions of the two-dimensional electron gas

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    Based on its known exact properties and a new set of extensive fixed-node reptation quantum Monte Carlo simulations (both with and without backflow correlations, which in this case turn out to yield negligible improvements), we propose a new analytical representation of (i) the spin-summed pair-distribution function and (ii) the spin-resolved potential energy of the ideal two-dimensional interacting electron gas for a wide range of electron densities and spin polarization, plus (iii) the spin-resolved pair-distribution function of the unpolarized gas. These formulae provide an accurate reference for quantities previously not available in analytic form, and may be relevant to semiconductor heterostructures, metal-insulator transitions and quantum dots both directly, in terms of phase diagram and spin susceptibility, and indirectly, as key ingredients for the construction of new two-dimensional spin density functionals, beyond the local approximation.Comment: 12 pages, 10 figures; misprints correcte

    A local density functional for the short-range part of the electron-electron interaction

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    Motivated by recent suggestions --to split the electron-electron interaction into a short-range part, to be treated within the density functional theory, and a long-range part, to be handled by other techniques-- we compute, with a diffusion Monte Carlo method, the ground-state energy of a uniform electron gas with a modified, short-range-only electron-electron interaction \erfc(\mu r)/r, for different values of the cutoff parameter μ\mu and of the electron density. After deriving some exact limits, we propose an analytic representation of the correlation energy which accurately fits our Monte Carlo data and also includes, by construction, these exact limits, thus providing a reliable ``short-range local-density functional''.Comment: 7 pages, 3 figure

    Regularity of higher codimension area minimizing integral currents

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    This lecture notes are an expanded version of the course given at the ERC-School on Geometric Measure Theory and Real Analysis, held in Pisa, September 30th - October 30th 2013. The lectures aim to explain the main steps of a new proof of the partial regularity of area minimizing integer rectifiable currents in higher codimension, due originally to F. Almgren, which is contained in a series of papers in collaboration with C. De Lellis (University of Zurich).Comment: This text will appear in "Geometric Measure Theory and Real Analysis", pp. 131--192, Proceedings of the ERC school in Pisa (2013), L. Ambrosio Ed., Edizioni SNS (CRM Series

    The cost of an ALP solution to the neutral BB-anomalies

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    The neutral anomalies in BB decays are analysed in terms of the tree-level exchange of an axion-like-particle (ALP), within the effective field theory framework. The complete two-dimensional parameter space for ALP couplings to electrons and muons is explored. The solutions to RKR_K and to the two energy bins of RKR_{K^\ast} are confronted with the impact of ALP exchange on other observables (meson oscillations, leptonic and semileptonic decays of BB mesons including searches for new resonances, astrophysical constraints), as well as with the theoretical domain of validity of the effective theory. Solutions based on ALPs heavier than BB mesons, or lighter than twice the muon mass, are shown to be excluded. In contrast, the exchange of on-shell ALPs provides solutions to RKR_K and/or RKR_{K^\ast} within 2σ2\sigma sensitivity which are technically compatible with those constraints; these solutions can be in addition compatible with the data on the g2g-2 of the electron but not simultaneously with those on the g2g-2 of the muon. Furthermore, a ''golden ALP mass'' is identified at the frontier between the two energy bin windows of RKR_{K^\ast}, which could simultaneously explain these two RKR_{K^\ast} anomalies together with RKR_K; this calls for the convenience of different energy binning which would easily clear up this (unlikely) possibility. The impact of smearing on data analysis is also discussed.Comment: 50 pages, 15 figure

    Pharmacokinetic profiles of the analgesic drug flupirtine in cats

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    Flupirtine (FLU) is a non-opioid analgesic drug with no antipyretic or antiphlogistic effects, used in the treatment of a wide range of pain states in human beings. There is a substantial body of evidence on the efficacy of FLU in humans but this is inadequate to recommend its off-label use in veterinary clinical practice. The aim of this study was to evaluate the pharmacokinetic profiles of FLU after IV and PO administration in healthy cats. Six mixed breed adult cats were randomly assigned to two treatment groups using an open, single-dose, two-treatment, two-phase, paired, cross-over design (2 × 2 Latin-square). Group 1 (n = 3) received a single dose of 5 mg/kg of FLU injected IV into the jugular vein. Group 2 (n = 3) received the same dose via PO route. The wash out period was 1 week. Blood samples (1 mL) were collected at assigned times and plasma was then analysed by a validated HPLC method.No adverse effects at the point of injection and no behavioural changes or alterations in health parameters were observed in the animals during or after the study (up to 7 days after the full study). After IV administration, FLU was detectable in plasma up to 36 h. After PO administration, FLU plasma concentrations were lower than those following IV administration, but they were detectable over the same time range. The terminal part of both mean pharmacokinetic curves showed a similar trend of elimination. The oral bioavailability was approximately 40%. This is the first study of FLU in an animal species of veterinary interest and it could pave the way for the use of this active ingredient in the veterinary field

    The impact of SuperB on flavour physics

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    This report provides a succinct summary of the physics programme of SuperB, and describes that potential in the context of experiments making measurements in flavour physics over the next 10 to 20 years. Detailed comparisons are made with Belle II and LHCb, the other B physics experiments that will run in this decade. SuperB will play a crucial role in defining the landscape of flavour physics over the next 20 years.Comment: 20 pages, 6 figure

    Transmission studies and the composition of prokaryotic communities associated with healthy and diseased Aplysina cauliformis sponges suggest that Aplysina Red Band Syndrome is a prokaryotic polymicrobial disease

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    Aplysina cauliformis, the Caribbean purple rope sponge, is commonly affected by Aplysina Red Band Syndrome (ARBS). This transmissible disease manifests as circular lesions with red margins and results in bare spongin fibers. Leptolyngbya spp. appear to be responsible for the characteristic red coloration but transmission studies with a sponge-derived isolate failed to establish disease, leaving the etiology of ARBS unknown. To investigate the cause of ARBS, contact transmission experiments were performed between healthy and diseased sponges separated by filters with varying pore sizes. Transmission occurred when sponges were separated by filters with pore sizes ≥ 2.5 μm, suggesting a prokaryotic pathogen(s) but not completely eliminating eukaryotic pathogen(s). Using 16S rRNA gene sequencing methods, 38 prokaryotic taxa were significantly enriched in diseased sponges, including Leptolyngbya, whereas seven taxa were only found in some, but not all, of the ARBS-affected sponges. These results do not implicate a single taxon, but rather a suite of taxa that changed in relative abundance with disease, suggesting a polymicrobial etiology as well as dysbiosis. As a better understanding of dysbiosis is gained, changes in the composition of associated prokaryotic communities may have increasing importance for evaluating and maintaining the health of individuals and imperiled coral reef ecosystems

    Vortex and half-vortex dynamics in a spinor quantum fluid of interacting polaritons

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    Spinorial or multi-component Bose-Einstein condensates may sustain fractional quanta of circulation, vorticant topological excitations with half integer windings of phase and polarization. Matter-light quantum fluids, such as microcavity polaritons, represent a unique test bed for realising strongly interacting and out-of-equilibrium condensates. The direct access to the phase of their wavefunction enables us to pursue the quest of whether half vortices ---rather than full integer vortices--- are the fundamental topological excitations of a spinor polariton fluid. Here, we are able to directly generate by resonant pulsed excitations, a polariton fluid carrying either the half or full vortex states as initial condition, and to follow their coherent evolution using ultrafast holography. Surprisingly we observe a rich phenomenology that shows a stable evolution of a phase singularity in a single component as well as in the full vortex state, spiraling, splitting and branching of the initial cores under different regimes and the proliferation of many vortex anti-vortex pairs in self generated circular ripples. This allows us to devise the interplay of nonlinearity and sample disorder in shaping the fluid and driving the phase singularities dynamicsComment: New version complete with revised modelization, discussion and added material. 8 pages, 7 figures. Supplementary videos: https://drive.google.com/folderview?id=0B0QCllnLqdyBfmc2ai0yVF9fa2g2VnZodGUwemVkLThBb3BoOVRKRDJMS2dUdjlZdkRTQk
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