Search results for "Separable space"
showing 10 items of 67 documents
Electric polarizability of nuclei from a longitudinal sum rule
1998
The nuclear electric polarizability is theoretically analyzed using a sum rule derived from the longitudinal part of the forward Compton amplitude. Beyond the leading dipole contribution, this approach leads to the presence of potential-dependent terms that do not show up in previous analyses. The significance of these new contributions is illustrated by performing an explicit calculation for a proton-neutron system interacting via a separable potential.
Couplings in coupled channels versus wave functions in the case of resonances: Application to the twoΛ(1405)states
2011
In this paper we develop a formalism to evaluate wave functions in momentum and coordinate space for the resonant states dynamically generated in a unitary coupled channel approach. The on-shell approach for the scattering matrix, commonly used, is also obtained in quantum mechanics with a separable potential, which allows one to write wave functions in a trivial way. We develop useful relationships among the couplings of the dynamically generated resonances to the different channels and the wave functions at the origin. The formalism provides an intuitive picture of the resonances in the coupled channel approach, as bound states of one bound channel, which decays into open ones. It also pr…
Energy-independent new physics in the flavour ratios of high-energy astrophysical neutrinos
2010
We have studied the consequences of breaking the CPT symmetry in the neutrino sector, using the expected high-energy neutrino flux from distant cosmological sources such as active galaxies. For this purpose we have assumed three different hypotheses for the neutrino production model, characterised by the flavour fluxes at production phi(0)(e) : phi(0)(mu) : phi(0)(tau) = 1 : 2 : 0, 0 : 1 : 0, and 1 : 0 : 0, and studied the theoretical and experimental expectations for the muon-neutrino flux at Earth, phi(mu), and for the flavour ratios at Earth, R = phi(mu)/phi(e) and S = phi(tau)/phi(mu). CPT violation (CPTV) has been implemented by adding an energy-independent term to the standard neutrin…
Low-energy scattering and photoproduction ofηmesons on three-body nuclei
2003
The optical potential approach for low-energy scattering of $\eta$-mesons on three-body nuclei is compared to an exact treatment of the $\eta 3N$ system using four-body scattering theory with separable interactions in s-waves only. The higher-order terms including the interaction of the struck nucleon with the surrounding nuclear medium and virtual target excitations in between successive $\eta$-scatterings are found to cause important corrections. Effects of final state interaction in $\eta$-photoproduction on $^3$H and $^3$He are also studied and sizable contributions beyond the optical model approach are found.
SKYRME-RANDOM-PHASE-APPROXIMATION DESCRIPTION OF SPIN-FLIP AND ORBITAL M1 GIANT RESONANCES
2010
The self-consistent separable random-phase approximation (SRPA) with Skyrme forces is extended to the case of magnetic excitations and applied to the description of spin-flip and orbital M1 giant resonances in the isotopic chain 142-152 Nd . The Skyrme forces SkT6, SkM*, SLy6 and SkI3 are used. The calculations show an onset of the scissors mode with increasing deformation. A specific three-peak structure of the spin-flip response is found and explained by particular neutron and proton spin-flip transitions. Although the employed forces provide an acceptable qualitative description, the Skyrme functional still needs further improvement to reproduce quantitatively the experiment for spin mo…
Binding of charmonium with two- and three-body nuclei
2006
The energies of the (eta_c d) and (eta_c 3He) bound states are calculated on the basis of exact three- and four-body AGS equations. For the eta_c N interaction a Yukawa-type potential has been adopted. The calculations are done for a certain range of its strength parameter. The results obtained are quite different from calculations based on the folding model.
Giant Monopole Resonances and nuclear incompressibilities studied for the zero-range and separable pairing interactions
2012
Background: Following the 2007 precise measurements of monopole strengths in tin isotopes, there has been a continuous theoretical effort to obtain a precise description of the experimental results. Up to now, there is no satisfactory explanation of why the tin nuclei appear to be significantly softer than 208Pb. Purpose: We determine the influence of finite-range and separable pairing interactions on monopole strength functions in semi-magic nuclei. Methods: We employ self-consistently the Quasiparticle Random Phase Approximation on top of spherical Hartree-Fock-Bogolyubov solutions. We use the Arnoldi method to solve the linear-response problem with pairing. Results: We found that the dif…
Generation of entanglement in systems of intercoupled qubits
2014
We consider systems of two and three qubits, mutually coupled by Heisenberg-type exchange interaction and interacting with external laser fields. We show that these systems allow one to create maximally entangled Bell states, as well as three qubit Greenberger-Horne-Zeilinger and W states. In particular, we point out that some of the target states are the eigenstates of the initial bare system. Due to this, one can create entangled states by means of pulse area and adiabatic techniques, when starting from a separable (non-entangled) ground state. On the other hand, for target states, not present initially in the eigensystem of the model, we apply the robust stimulated Raman adiabatic passag…
Interaction-free evolving states of a bipartite system
2014
We show that two interacting physical systems may admit entangled pure or non separable mixed states evolving in time as if the mutual interaction hamiltonian were absent. In this paper we define these states Interaction Free Evolving (IFE) states and characterize their existence for a generic binary system described by a time independent Hamiltonian. A comparison between IFE subspace and the decoherence free subspace is reported. The set of all pure IFE states is explicitly constructed for a non homogeneous spin star system model.
FINITE-RANGE SEPARABLE PAIRING INTERACTION WITHIN NEW N[sup 3]LO DFT APPROACH
2011
For over four decades, the Skyrme functional within various parametrizations has been used to calculate nuclear properties. In the last few years there was a number of attempts to improve its performance and introduce generalized forms. In particular, the most general phenomenologi‐cal quasi‐local energy density functional, which contains all combinations of density, spin‐density, and their derivatives up to the sixth order (N3LO), was proposed in reference [1]. Since in the phe‐nomenological functional approaches the particle‐particle (pp) interaction channel is treated independently from the particle‐hole (ph) channel, there remains a question of what pairing interaction is suitable to us…