104 research outputs found

    Neutrino mass in GUT constrained supersymmetry with R-parity violation in light of neutrino oscillations

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    The neutrino masses are generated in grand unified theory (GUT) constrained supersymmetric model with R-parity violation. The neutrinos acquire masses via tree-level neutrino-neutralino mixing as well as via one-loop radiative corrections. The theoretical mass matrix is compared with the phenomenological one, which is reconstructed by using neutrino oscillation and neutrinoless double beta decay data. This procedure allows to obtain significantly stronger constraints on R-parity breaking parameters than those existing in the literature. The implication of normal and inverted neutrino mass hierarchy on the sneutrino expectation values, lepton-Higgs bilinear and trilinear R-parity breaking couplings is also discussed

    Correlation energies by the generator coordinate method: computational aspects for quadrupolar deformations

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    We investigate truncation schemes to reduce the computational cost of calculating correlations by the generator coordinate method based on mean-field wave functions. As our test nuclei, we take examples for which accurate calculations are available. These include a strongly deformed nucleus, 156Sm, a nucleus with strong pairing, 120Sn, the krypton isotope chain which contains examples of soft deformations, and the lead isotope chain which includes the doubly magic 208Pb. We find that the Gaussian overlap approximation for angular momentum projection is effective and reduces the computational cost by an order of magnitude. Cost savings in the deformation degrees of freedom are harder to realize. A straightforward Gaussian overlap approximation can be applied rather reliably to angular-momentum projected states based on configuration sets having the same sign deformation (prolate or oblate), but matrix elements between prolate and oblate deformations must be treated with more care. We propose a two-dimensional GOA using a triangulation procedure to treat the general case with both kinds of deformation. With the computational gains from these approximations, it should be feasible to carry out a systematic calculation of correlation energies for the nuclear mass table.Comment: 11 pages revtex, 9 eps figure

    Intrinsic symmetries

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    In this paper a concept of symmetry in the parameter space of the parameter dependent Hamiltonians is considered. The three different ways of realization of this symmetry is introduced. The example of analysis of this kind of symmetries is made in case of spherical harmonic oscillator. Some consequences of this symmetry for the electric type transition amplitudes of the electromagnetic nuclear radiation is shown

    Mesoscopic theory for size- and charge- asymmetric ionic systems. I. Case of extreme asymmetry

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    A mesoscopic theory for the primitive model of ionic systems is developed for arbitrary size, λ=σ+/σ\lambda=\sigma_+/\sigma_-, and charge, Z=e+/eZ=e_+/|e_-|, asymmetry. Our theory is an extension of the theory we developed earlier for the restricted primitive model. The case of extreme asymmetries λ\lambda\to\infty and ZZ \to\infty is studied in some detail in a mean-field approximation. The phase diagram and correlation functions are obtained in the asymptotic regime λ\lambda\to\infty and ZZ \to\infty, and for infinite dilution of the larger ions (volume fraction np1/Zn_p\sim 1/Z or less). We find a coexistence between a very dilute 'gas' phase and a crystalline phase in which the macroions form a bcc structure with the lattice constant 3.6σ+\approx 3.6\sigma_+. Such coexistence was observed experimentally in deionized aqueous solutions of highly charged colloidal particles

    Field theory for size- and charge asymmetric primitive model of electrolytes. Mean-field stability analysis and pretransitional effects

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    The primitive model of ionic systems is investigated within a field-theoretic description for the whole range of size-, \lambda, and charge, Z, ratios of the two ionic species. Two order parameters (OP) are identified, and their relations to physically relevant quantities are described for various values of \lambda and Z. Instabilities of the disordered phase associated with the two OP's are determined in the mean-field approximation. A gas-liquid separation occurs for any Z and \lambda different from 1. In addition, an instability with respect to various types of periodic ordering of the two kinds of ions is found

    A Variational Level Set Approach for Surface Area Minimization of Triply Periodic Surfaces

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    In this paper, we study triply periodic surfaces with minimal surface area under a constraint in the volume fraction of the regions (phases) that the surface separates. Using a variational level set method formulation, we present a theoretical characterization of and a numerical algorithm for computing these surfaces. We use our theoretical and computational formulation to study the optimality of the Schwartz P, Schwartz D, and Schoen G surfaces when the volume fractions of the two phases are equal and explore the properties of optimal structures when the volume fractions of the two phases not equal. Due to the computational cost of the fully, three-dimensional shape optimization problem, we implement our numerical simulations using a parallel level set method software package.Comment: 28 pages, 16 figures, 3 table

    Fluctuations of elastic interfaces in fluids: Theory and simulation

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    We study the dynamics of elastic interfaces-membranes-immersed in thermally excited fluids. The work contains three components: the development of a numerical method, a purely theoretical approach, and numerical simulation. In developing a numerical method, we first discuss the dynamical coupling between the interface and the surrounding fluids. An argument is then presented that generalizes the single-relaxation time lattice-Boltzmann method for the simulation of hydrodynamic interfaces to include the elastic properties of the boundary. The implementation of the new method is outlined and it is tested by simulating the static behavior of spherical bubbles and the dynamics of bending waves. By means of the fluctuation-dissipation theorem we recover analytically the equilibrium frequency power spectrum of thermally fluctuating membranes and the correlation function of the excitations. Also, the non-equilibrium scaling properties of the membrane roughening are deduced, leading us to formulate a scaling law describing the interface growth, W^2(L,T)=L^3 g[t/L^(5/2)], where W, L and T are the width of the interface, the linear size of the system and the temperature respectively, and g is a scaling function. Finally, the phenomenology of thermally fluctuating membranes is simulated and the frequency power spectrum is recovered, confirming the decay of the correlation function of the fluctuations. As a further numerical study of fluctuating elastic interfaces, the non-equilibrium regime is reproduced by initializing the system as an interface immersed in thermally pre-excited fluids.Comment: 15 pages, 11 figure

    Self-Assembled Triply Periodic Minimal Surfaces as moulds for Photonic Band Gap Materials

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    We propose systems with structures defined by self-assembled triply periodic minimal surfaces (STPMS) as candidates for photonic bandgap materials. To support our proposal we have calculated the photonic bands for different STPMS and we have found that, at least, the double diamond and gyroid structures present full photonic bandgaps. Given the great variety of systems which crystalize in these structures, the diversity of possible materials that form them and the range of lattice constants they present, the construction of photonic bandgap materials with gaps in the visible range may be presently within reach.Comment: 3 pages, 2 figures, RevTe

    Strong-Segregation Theory of Bicontinuous Phases in Block Copolymers

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    We compute phase diagrams for AnBmA_nB_m starblock copolymers in the strong-segregation regime as a function of volume fraction ϕ\phi, including bicontinuous phases related to minimal surfaces (G, D, and P surfaces) as candidate structures. We present the details of a general method to compute free energies in the strong segregation limit, and demonstrate that the gyroid G phase is the most nearly stable among the bicontinuous phases considered. We explore some effects of conformational asymmetry on the topology of the phase diagram.Comment: 14 pages, latex, 21 figures, to appear in Macromolecule
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