57,466 research outputs found

    Transport through a single Anderson impurity coupled to one normal and two superconducting leads

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    We study the interplay between the Kondo and Andreev-Josephson effects in a quantum dot coupled to one normal and two superconducting (SC) leads. In the large gap limit, the low-energy states of this system can be described exactly by a local Fermi liquid for the interacting Bogoliubov particles. The phase shift and the renormalized parameters for the Bogoliubov particles vary depending on the Josephson phase between the two SC leads. We explore the precise features of a crossover that occurs between the Kondo singlet and local Cooper-pairing states as the Josephson phase varies, using the numerical renormalization group approach.Comment: 4 pages, 4 figures, contribution to SCES 201

    Basic oscillation measurables in the neutrino pair beam

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    It is shown that the vector current contribution of neutrino interaction with electrons in ion gives rise to oscillating component, which is absent for the axial-vector contribution, when a single neutrino is detected in the recently proposed neutrino pair beam. CP violation measurements are thus possible with high precision along with determination of mass hierarchical patterns.Comment: 10 pages, 9 figure

    Computation accuracies of boundary element method and finite element method in transient eddy current analysis

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    The computation accuracies of the boundary-element method (BEM) and finite-element method (FEM) in transient eddy-current problems are compared by using a slot-embedded conductor model and a diffusion model that can be solved theoretically. For computing the vector potential or magnetic flux density it is shown that larger time-step width can be chosen in the BEM than in the FEM method for the same accuracy </p

    A mean field theory of coded CDMA systems

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    We present a mean field theory of code-division multiple access (CDMA) systems with error-control coding. On the basis of the relation between the free energy and mutual information, we obtain an analytical expression of the maximum spectral efficiency of the coded CDMA system, from which a mean field description of the coded CDMA system is provided in terms of a bank of scalar Gaussian channels whose variances in general vary at different code symbol positions. Regular low-density parity-check (LDPC)-coded CDMA systems are also discussed as an example of the coded CDMA systems

    A Novel Approach in Constraining Electron Spectra in Blazar Jets: The Case of Markarian 421

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    We report results from the observations of the well studied TeV blazar Mrk 421 with the Swift and the Suzaku satellites in December 2008. During the observation, Mrk 421 was found in a relatively low activity state, with the corresponding 2-10 keV flux of 3×10103 \times 10^{-10} erg/s/cm^2. For the purpose of robust constraining the UV-to-X-ray emission continuum we selected only the data corresponding to truly simultaneous time intervals between Swift and Suzaku, allowing us to obtain a good-quality, broad-band spectrum despite a modest length (0.6 ksec) exposure. We analyzed the spectrum with the parametric forward-fitting SYNCHROTRON model implemented in XSPEC assuming two different representations of the underlying electron energy distribution, both well motivated by the current particle acceleration models: a power-law distribution above the minimum energy γmin\gamma_{\rm min} with an exponential cutoff at the maximum energy γmax\gamma_{\rm max}, and a modified ultra-relativistic Maxwellian with an equilibrium energy γeq\gamma_{\rm eq}. We found that the latter implies unlikely physical conditions within the blazar zone of Mrk 421. On the other hand, the exponentially moderated power-law electron distribution gives two possible sets of the model parameters: (i) flat spectrum dNe/dγγ1.91dN'_e/d\gamma \propto \gamma^{-1.91} with low minimum electron energy γmin<103\gamma_{\rm min}<10^3, and (ii) steep spectrum γ2.77\propto \gamma^{-2.77} with high minimum electron energy γmin2×104\gamma_{\rm min}\simeq 2\times10^4. We discuss different interpretations of both possibilities in the context of a diffusive acceleration of electrons at relativistic, sub- or superluminal shocks. We also comment on how exactly the gamma-ray data can be used to discriminate between the proposed different scenarios.Comment: 18 pages, 2 figures; accepted for publication in the Astrophysical Journa
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