1,598 research outputs found

    On dynamical adjoint functor

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    We give an explicit formula relating the dynamical adjoint functor and dynamical twist over nonalbelian base to the invariant pairing on parabolic Verma modules. As an illustration, we give explicit U(sl(n))U(sl(n))- and Uâ„Ź(sl(n))U_\hbar(sl(n))-invariant star product on projective spaces

    On the Bethe Ansatz for the Jaynes-Cummings-Gaudin model

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    We investigate the quantum Jaynes-Cummings model - a particular case of the Gaudin model with one of the spins being infinite. Starting from the Bethe equations we derive Baxter's equation and from it a closed set of equations for the eigenvalues of the commuting Hamiltonians. A scalar product in the separated variables representation is found for which the commuting Hamiltonians are Hermitian. In the semi classical limit the Bethe roots accumulate on very specific curves in the complex plane. We give the equation of these curves. They build up a system of cuts modeling the spectral curve as a two sheeted cover of the complex plane. Finally, we extend some of these results to the XXX Heisenberg spin chain.Comment: 16 page

    Polarized radio emission from extensive air showers measured with LOFAR

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    We present LOFAR measurements of radio emission from extensive air showers. We find that this emission is strongly polarized, with a median degree of polarization of nearly 99%99\%, and that the angle between the polarization direction of the electric field and the Lorentz force acting on the particles, depends on the observer location in the shower plane. This can be understood as a superposition of the radially polarized charge-excess emission mechanism, first proposed by Askaryan and the geomagnetic emission mechanism proposed by Kahn and Lerche. We calculate the relative strengths of both contributions, as quantified by the charge-excess fraction, for 163163 individual air showers. We find that the measured charge-excess fraction is higher for air showers arriving from closer to the zenith. Furthermore, the measured charge-excess fraction also increases with increasing observer distance from the air shower symmetry axis. The measured values range from (3.3±1.0)%(3.3\pm 1.0)\% for very inclined air showers at 25 m25\, \mathrm{m} to (20.3±1.3)%(20.3\pm 1.3)\% for almost vertical showers at 225 m225\, \mathrm{m}. Both dependencies are in qualitative agreement with theoretical predictions.Comment: 22 pages, 14 figures, accepted for publication in JCA

    A method for high precision reconstruction of air shower Xmax using two-dimensional radio intensity profiles

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    The mass composition of cosmic rays contains important clues about their origin. Accurate measurements are needed to resolve long-standing issues such as the transition from Galactic to extragalactic origin, and the nature of the cutoff observed at the highest energies. Composition can be studied by measuring the atmospheric depth of the shower maximum Xmax of air showers generated by high-energy cosmic rays hitting the Earth's atmosphere. We present a new method to reconstruct Xmax based on radio measurements. The radio emission mechanism of air showers is a complex process that creates an asymmetric intensity pattern on the ground. The shape of this pattern strongly depends on the longitudinal development of the shower. We reconstruct Xmax by fitting two-dimensional intensity profiles, simulated with CoREAS, to data from the LOFAR radio telescope. In the dense LOFAR core, air showers are detected by hundreds of antennas simultaneously. The simulations fit the data very well, indicating that the radiation mechanism is now well-understood. The typical uncertainty on the reconstruction of Xmax for LOFAR showers is 17 g/cm^2.Comment: 12 pages, 10 figures, submitted to Phys. Rev.

    The radio emission pattern of air showers as measured with LOFAR - a tool for the reconstruction of the energy and the shower maximum

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    The pattern of the radio emission of air showers is finely sampled with the Low-Frequency ARray (LOFAR). A set of 382 measured air showers is used to test a fast, analytic parameterization of the distribution of pulse powers. Using this parameterization we are able to reconstruct the shower axis and give estimators for the energy of the air shower as well as the distance to the shower maximum.Comment: 15 pages, 10 figures, accepted for publication in JCA

    Penetration of Josephson vortices and measurement of the c-axis penetration depth in Bi2Sr2CaCu2O8+δBi_{2}Sr_{2}CaCu_{2}O_{8+\delta}: Interplay of Josephson coupling, surface barrier and defects

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    The first penetration field H_{J}(T) of Josephson vortices is measured through the onset of microwave absorption in the locked state, in slightly overdoped Bi2Sr2CaCu2O8+δ\rm{Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta}} single crystals (T_{c} ~ 84 K). The magnitude of H_{J}(T) is too large to be accounted for by the first thermodynamic critical field H_{c1}(T). We discuss the possibility of a Bean-Livingston barrier, also supported by irreversible behavior upon flux exit, and the role of defects, which relates H_{J}(T) to the c-axis penetration depth λc(T)\lambda_{c}(T). The temperature dependence of the latter, determined by a cavity perturbation technique and a theoretical estimate of the defect-limited penetration field are used to deduce from H_{J}(T) the absolute value of λc(0)=(35±15)μm\lambda_{c}(0)=(35 \pm 15) \mu m.Comment: 9 pages, 6 figure

    On the Quantum Inverse Problem for the Closed Toda Chain

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    We reconstruct the canonical operators pi,qip_i,q_i of the quantum closed Toda chain in terms of Sklyanin's separated variables.Comment: 16 page

    Coccidioides immitis presenting with acute hydropneumothorax in an immunocompetent patient from South Texas

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    Coccidioidomycosis is a disease caused by the dimorphic fungi Coccidioides immitis and Coccidioides posadasii that predominates in dry climates and it is endemic in Southern California and Arizona. Coccidioides is also found in parts of West Texas and a long the Rio Grande River, however, incidence tends to decrease in areas close to the Gulf of Mexico due to increased humidity. Coccidioidomycosis is more commonly a subclinical and self-limited disease in up to sixty percent of cases. Acute pneumonia (Valley fever), extra thoracic disseminated infection and complications occur more frequently in immunocompromised hosts. We present a case of severe coccidiomycosis in an immunocompetent host who lived in central California for two months, 2 years prior to manifesting severe respiratory compromise. Clinicians should be able to recognize differential diagnoses for cavitary-like lung lesions, paying close attention to social history and CDC epidemiology data
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