551 research outputs found

    Reply to comment ``On the test of the modified BCS at finite temperature''

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    This is our formal Reply to revised version (v2) of arXiv: nucl-th/0510004v2.Comment: accepted in Physical Review

    Test of modified BCS model at finite temperature

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    A recently suggested modified BCS (MBCS) model has been studied at finite temperature. We show that this approach does not allow the existence of the normal (non-superfluid) phase at any finite temperature. Other MBCS predictions such as a negative pairing gap, pairing induced by heating in closed-shell nuclei, and ``superfluid -- super-superfluid'' phase transition are discussed also. The MBCS model is tested by comparing with exact solutions for the picket fence model. Here, severe violation of the internal symmetry of the problem is detected. The MBCS equations are found to be inconsistent. The limit of the MBCS applicability has been determined to be far below the ``superfluid -- normal'' phase transition of the conventional FT-BCS, where the model performs worse than the FT-BCS.Comment: 8 pages, 9 figures, to appear in PR

    Self-consistent calculations of quadrupole moments of the first 2+ states in Sn and Pb isotopes

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    A method of calculating static moments of excited states and transitions between excited states is formulated for non-magic nuclei within the Green function formalism. For these characteristics, it leads to a noticeable difference from the standard QRPA approach. Quadrupole moments of the first 2+ states in Sn and Pb isotopes are calculated using the self-consistent TFFS based on the Energy Density Functional by Fayans et al. with the set of parameters DF3-a fixed previously. A reasonable agreement with available experimental data is obtained.Comment: 5 pages, 6 figure

    Inelastic neutrino scattering off hot nuclei in supernova environments

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    We study inelastic neutrino scattering off hot nuclei for temperatures relevant under supernova conditions. The method we use is based on the quasiparticle random phase approximation extended to finite temperatures within the thermo field dynamics (TQRPA). The method allows a transparent treatment of upward and downward transitions in hot nuclei, avoiding the application of Brink's hypothesis. For the sample nuclei 56^{56}Fe and 82^{82}Ge we perform a detailed analysis of thermal effects on the strength distributions of allowed Gamow-Teller (GT) transitions which dominate the scattering process at low neutrino energies. For 56^{56}Fe and 82^{82}Ge the finite temperature cross-sections are calculated by taking into account the contribution of allowed and forbidden transitions. The observed enhancement of the cross-section at low neutrino energies is explained by considering thermal effects on the GT strength. For 56^{56}Fe we compare the calculated cross-sections to those obtained earlier from a hybrid approach that combines large-scale shell-model and RPA calculations.Comment: 12 pages, 9 figure

    Gamow-Teller strength distributions at finite temperatures and electron capture in stellar environments

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    We propose a new method to calculate stellar weak-interaction rates. It is based on the Thermo-Field-Dynamics formalism and allows the calculation of the weak-interaction response of nuclei at finite temperatures. The thermal evolution of the GT+_+ distributions is presented for the sample nuclei 54,56^{54, 56}Fe and ~76,78,80^{76,78,80}Ge. For Ge we also calculate the strength distribution of first-forbidden transitions. We show that thermal effects shift the GT+_+ centroid to lower excitation energies and make possible negative- and low-energy transitions. In our model we demonstrate that the unblocking effect for GT+_+ transitions in neutron-rich nuclei is sensitive to increasing temperature. The results are used to calculate electron capture rates and are compared to those obtained from the shell model.Comment: 16 pages, 9 figure

    Weight functions of light shield and the signal at the input of optical sensor at the intersection of the bullets of light shield

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    In this article, the definition of weight functions of a light shield at the intersection of the bullet in different field areas of shield registration is considered. The signal definition at the input of an optical sensor at the intersection of the bullet of a light shield is viewed. The research results can be used in considering the facts that can influence on the error estimation of the coordinate determination when a bullet hits the target

    The 33-closure of a solvable permutation group is solvable

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    Let mm be a positive integer and let Ω\Omega be a finite set. The mm-closure of GSym(Ω)G\leq\operatorname{Sym}(\Omega) is the largest permutation group on Ω\Omega having the same orbits as GG in its induced action on the Cartesian product Ωm\Omega^m. The 11-closure and 22-closure of a solvable permutation group need not be solvable. We prove that the mm-closure of a solvable permutation group is always solvable for m3m\geq3
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