12,304 research outputs found

    Gamow-Teller strength distributions in Fe and Ni stable isotopes

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    We study Gamow-Teller strength distributions in some selected nuclei of particular Astrophysical interest within the iron mass region. The theoretical framework is based on a proton-neutron Quasiparticle Random Phase Approximation built on a deformed selfconsistent mean field basis obtained from two-body density-dependent Skyrme forces. We compare our results to available experimental information obtained from (n,p) and (p,n) charge exchange reactions.Comment: 11 pages, 3 figure

    Isospin mixing and Fermi transitions: Selfconsistent deformed mean field calculations and beyond

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    We study Fermi transitions and isospin mixing in an isotopic chain 70-78 Kr considering various approximations that use the same Skyrme-Hartree-Fock single particle basis. We study Coulomb effects as well as the effect of BCS and quasiparticle random phase approximation (QRPA) correlations. A measure of isospin mixing in the approximate ground state is defined by means of the expectation value of the isospin operator squared in N=Z nuclei (which is generalized to N different from Z nuclei). Starting from strict Hartree-Fock approach without Coulomb, it is shown that the isospin breaking is negligible, on the order of a few per thousand for (N-Z)=6, increasing to a few percent with Coulomb. Pairing correlations induce rather large isospin mixing and Fermi transitions of the forbidden type (beta- for NZ). The enhancement produced by BCS correlations is compensated to a large extent by QRPA correlations induced by isospin conserving residual interactions that tend to restore isospin symmetry.Comment: 14 pages, 5 figures, to be published in Phys. Rev.

    Structure and three-body decay of 9^9Be resonances

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    The complex-rotated hyperspherical adiabatic method is used to study the decay of low-lying 9^9Be resonances into one neutron and two α\alpha-particles. We investigate the six resonances above the break-up threshold and below 6 MeV: 1/2±1/2^\pm, 3/2±3/2^\pm and 5/2±5/2^\pm. The short-distance properties of each resonance are studied, and the different angular momentum and parity configurations of the 8^8Be and 5^5He two-body substructures are determined. We compute the branching ratio for sequential decay via the 8^8Be ground state which qualitatively is consistent with measurements. We extract the momentum distributions after decay directly into the three-body continuum from the large-distance asymptotic structures. The kinematically complete results are presented as Dalitz plots as well as projections on given neutron and α\alpha-energy. The distributions are discussed and in most cases found to agree with available experimental data.Comment: 12 pages, 10 figures. To appear in Physical Review

    Momentum distributions from three-body decaying 9Be and 9B resonances

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    The complex-rotated hyperspherical adiabatic method is used to study the decay of low-lying 9^9Be and 9^9B resonances into α\alpha, α\alpha and nn or pp. We consider six low-lying resonances of 9^9Be (1/2±1/2^\pm, 3/2±3/2^\pm and 5/2±5/2^\pm) and one resonance of 9^9B (5/25/2^-) to compare with. The properties of the resonances at large distances are decisive for the momentum distributions of the three decaying fragments. Systematic detailed energy correlations of Dalitz plots are presented.Comment: 4 pages, 2 figures. Proceedings of the SOTANCP2 conference held in Brussels in May 201

    Algorithmic quantum simulation of memory effects

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    We propose a method for the algorithmic quantum simulation of memory effects described by integrodifferential evolution equations. It consists in the systematic use of perturbation theory techniques and a Markovian quantum simulator. Our method aims to efficiently simulate both completely positive and nonpositive dynamics without the requirement of engineering non-Markovian environments. Finally, we find that small error bounds can be reached with polynomially scaling resources, evaluated as the time required for the simulation
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