1,085 research outputs found

    Seismic scattering and absorption mapping from intermediate-depth earthquakes reveals complex tectonic interactions acting in the Vrancea region and surroundings (Romania)

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    The present study was performed during a stay at the University of Münster financed by a grant awarded by the German Academic Exchange Service (DAAD) in 2014. Data used in the present study were provided by the National Institute for Earth Physics (Romania) and processed within the National Data Centre in Magurele. Seismic Analysis Code (SAC) (Goldstein and Snoke, 2005) and GMT (Wessel et al., 2013) codes were used. We thank the College of Physical Sciences (University of Aberdeen) and the Santander Mobility Award for providing travel grant to LDS to complete this manuscript. We are grateful as well to the anonymous reviewer for his useful remarks which helped us to improve the paper.Peer reviewedPostprin

    Determination of ground state properties in quantum spin systems by single qubit unitary operations and entanglement excitation energies

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    We introduce a method for analyzing ground state properties of quantum many body systems, based on the characterization of separability and entanglement by single subsystem unitary operations. We apply the method to the study of the ground state structure of several interacting spin-1/2 models, described by Hamiltonians with different degrees of symmetry. We show that the approach based on single qubit unitary operations allows to introduce {\it ``entanglement excitation energies''}, a set of observables that can characterize ground state properties, including the quantification of single-site entanglement and the determination of quantum critical points. The formalism allows to identify the existence and location of factorization points, and a purely quantum {\it ``transition of entanglement''} that occurs at the approach of factorization. This kind of quantum transition is characterized by a diverging ratio of excitation energies associated to single-qubit unitary operations.Comment: To appear in Phys. Rev.

    Can Fiscal Budget-Neutral Reforms Stimulate Growth? Model-Based Results

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    This paper focuses on growth enhancing budget-neutral fiscal reforms, i.e. changes in the composition of government revenues and spending that stimulate GDP growth while keeping the ratio of the fiscal budget to GDP constant. To this aim, we present simulation results using a multi-country DSGE model with three large economic regions, the US, the euro area and the rest of the world. The model features constrained and unconstrained non-Ricardian households and a detailed government sector; its multi-country nature allows investigating cross-country spillovers. The paper focuses on the most growth-friendly budget-neutral fiscal measures: (i) an incomplete fiscal devaluation (ii) a rise in government investment compensated by a fall in government consumption and (iii) a rise in government investment compensated by a rise in consumption and labor taxes. Dampening or amplifying effects due to coordination across policies (monetary and fiscal) and across economic regions are also considered. Three main results stand out. First, an increase in government investment financed by rising less distortionary taxes appears to be an effective growth-friendly budget-neutral reform in the sense that it generates both short- and long-run GDP growth and improves fiscal sustainability. Second, benefits and costs of budget-neutral reforms are not equally distributed across agents, giving rise to a policy trade-off between growth and distributional consequences. Third, budget-neutral reforms do not have large cross-border trade spillovers; however, reforms coordinated across all countries in periods of accommodative monetary policy do have amplified domestic effects

    The Interconnected Magmatic Plumbing System of the Natron Rift

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    Understanding the magmatic plumbing system of rift volcanoes is essential when examining the interplay between magmatic and tectonic forces. Recent seismicity, volcanic activity, magma emplacement, and volatile release make the Natron basin the ideal location to study these processes in the East African Rift System. Here, we present the first high-resolution tomographic imaging of Oldoinyo Lengai volcano and surrounding volcanic systems using attenuation mapping. High scattering and absorption features reveal fluid-filled fracture networks below regions of magmatic volatile release at the surface and a close spatial association between carbonatite volcanism and deeply penetrating, fluid-filled faults. High-absorption features appear sensitive to fluids and thermal gradients, revealing a central sill complex and connected plumbing system down to the mid-crust, which links volcanoes and rift segments across the developing magmatic rift

    Optimal estimation of losses at the ultimate quantum limit with non-Gaussian states

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    We address the estimation of the loss parameter of a bosonic channel probed by arbitrary signals. Unlike the optimal Gaussian probes, which can attain the ultimate bound on precision asymptotically either for very small or very large losses, we prove that Fock states at any fixed photon number saturate the bound unconditionally for any value of the loss. In the relevant regime of low-energy probes, we demonstrate that superpositions of the first low-lying Fock states yield an absolute improvement over any Gaussian probe. Such few-photon states can be recast quite generally as truncations of de-Gaussified photon-subtracted states.Comment: 4 pages, 3 figure

    A Microfluidic Device Based on Standing Surface Acoustic Waves for Sorting and Trapping Microparticles

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    Microfluidic devices can provide innovative means to handle and control the transport of (bio)particles within a fluid flow. The advantage of microscale devices is that different components can be integrated in a single chip at low cost, with a negligible power consumption, compared to alternative solutions. In this work, a numerical investigation is developed on the use of standing surface acoustic waves (SAWs) generated within a microfluidic channel in order to manipulate microparticles. Far-field waves are generated via inter-digital transducers (IDTs), travel on the surface of a piezoelectric substrate and finally interfere in the channel, giving rise to a standing wave solution in terms of acoustic pressure. Results are reported for different geometries of the channel, to define the sensitivity of the acoustic pressure field to the relevant geometric features of the channel. This investigation shows how the acoustic radiation and drag forces interact with each other to move and focus the particles, possibly leading to a separation of heterogeneous ones, and generally provide a way to manipulate them at a small scale

    On entanglement in neutrino mixing and oscillations

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    We report on recent results about entanglement in the context of particle mixing and oscillations. We study in detail single-particle entanglement arising in two-flavor neutrino mixing. The analysis is performed first in the context of Quantum Mechanics, and then for the case of Quantum Field Theory.Comment: 14 pages, 2 figures. Presented at "Symmetries in Science Symposium - Bregenz 2009"

    Seismic scattering and absorption mapping of debris flows, feeding paths, and tectonic units at Mount St. Helens volcano

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    Acknowledgments We thank Edoardo Del Pezzo, Ludovic Margerin, Haruo Sato, Mare Yamamoto, Tatsuhiko Saito, Malcolm Hole, and Seth Moran for the valuable suggestions regarding the methodology and interpretation. Greg Waite provided the P wave velocity model of MSH. An important revision of the methods was done after two blind reviews performed before submission. The suggestions of two anonymous reviewers greatly enhanced our ability of imaging structures, interpreting our results, and testing their reliability. The facilities of the IRIS Data Management System, and specifically the IRIS Data Management Center, were used for access to waveform and metadata required in this study, and provided by the Cascades Volcano Observatory – USGS. Interaction with geologists and geographers part of the Landscape Dynamics Theme of the Scottish Alliance for Geoscience, Environment and Society (SAGES) has been important for the interpretation of the results.Peer reviewedPostprin
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