758 research outputs found

    New Treatment of Resonances with Bound State Approximation by Using Pseudo Potential

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    We propose a new approach to extract the wave functions of resonances by the bound state approximation which gives the mixed states of the resonance components and the continuum ones. In our approach, on the basis of the method of analytic continuation in the coupling constant (ACCC), we construct Pad\'e rational function by adopting the positive energies as well as the negative ones. We report the result of the application of this new method to the second 2+2^+ state of 12^{12}C which was studied with the ACCC method in our previous work. It is found that the resonance parameters obtained by the ACCC method are well reproduced by the new method. Some advantages over the ACCC method are also shown.Comment: 10pages, 2figures, submitted to Prog. Theor. Phys, changed content, added reference

    Alpha-particle condensation in nuclei

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    A round up of the present status of the conjecture that n alpha nuclei form an alpha-particle condensate in excited states close to the n alpha threshold is given. Experiments which could demonstrate the condensate character are proposed. Possible lines of further theoretical developments are discussed.Comment: 6 page

    Analysis of previous microscopic calculations for second 0+0^+ state in 12^{12}C in terms of 3-alpha particle Bose-condensed state

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    The wave function of the second 0+0^+ state of 12^{12}C which was obtained long time ago by solving the microscopic 3α\alpha problem is shown to be almost completely equivalent to the wave function of the 3α\alpha condensed state which has been proposed recently by the present authors. This equivalence of the wave functions is shown to hold in two cases where different effective two-nucleon forces are adopted. This finding gives strong support for interpreting the second 0+0^+ state of 12^{12}C which is the key state for the synthesis of 12^{12}C in stars ('Hoyle' state), and which is one of the typical mysterious 0+0^+ states in light nuclei, as a gas-like structure of three α\alpha particles, Bose-condensed into an identical s-wave function.Comment: revtex, 5 pages, 2 figures, submitted to Phys. Rev.

    Monopole Excitation to Cluster States

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    We discuss strength of monopole excitation of the ground state to cluster states in light nuclei. We clarify that the monopole excitation to cluster states is in general strong as to be comparable with the single particle strength and shares an appreciable portion of the sum rule value in spite of large difference of the structure between the cluster state and the shell-model-like ground state. We argue that the essential reasons of the large strength are twofold. One is the fact that the clustering degree of freedom is possessed even by simple shell model wave functions. The detailed feature of this fact is described by the so-called Bayman-Bohr theorem which tells us that SU(3) shell model wave function is equivalent to cluster model wave function. The other is the ground state correlation induced by the activation of the cluster degrees of freedom described by the Bayman-Bohr theorem. We demonstrate, by deriving analytical expressions of monopole matrix elements, that the order of magnitude of the monopole strength is governed by the first reason, while the second reason plays a sufficient role in reproducing the data up to the factor of magnitude of the monopole strength. Our explanation is made by analysing three examples which are the monopole excitations to the 02+0^+_2 and 03+0^+_3 states in 16^{16}O and the one to the 02+0^+_2 state in 12^{12}C. The present results imply that the measurement of strong monopole transitions or excitations is in general very useful for the study of cluster states.Comment: 11 pages, 1 figure: revised versio

    Fluctuations for the Ginzburg-Landau ϕ\nabla \phi Interface Model on a Bounded Domain

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    We study the massless field on Dn=D1nZ2D_n = D \cap \tfrac{1}{n} \Z^2, where DR2D \subseteq \R^2 is a bounded domain with smooth boundary, with Hamiltonian \CH(h) = \sum_{x \sim y} \CV(h(x) - h(y)). The interaction \CV is assumed to be symmetric and uniformly convex. This is a general model for a (2+1)(2+1)-dimensional effective interface where hh represents the height. We take our boundary conditions to be a continuous perturbation of a macroscopic tilt: h(x)=nxu+f(x)h(x) = n x \cdot u + f(x) for xDnx \in \partial D_n, uR2u \in \R^2, and f ⁣:R2Rf \colon \R^2 \to \R continuous. We prove that the fluctuations of linear functionals of h(x)h(x) about the tilt converge in the limit to a Gaussian free field on DD, the standard Gaussian with respect to the weighted Dirichlet inner product (f,g)β=Diβiifiigi(f,g)_\nabla^\beta = \int_D \sum_i \beta_i \partial_i f_i \partial_i g_i for some explicit β=β(u)\beta = \beta(u). In a subsequent article, we will employ the tools developed here to resolve a conjecture of Sheffield that the zero contour lines of hh are asymptotically described by SLE(4)SLE(4), a conformally invariant random curve.Comment: 58 page

    Alpha Decay Width of 212^{212}Po from a quartetting wave function approach

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    A microscopic calculation of α\alpha-cluster preformation probability and α\alpha decay width in the typical α\alpha emitter 212^{212}Po is presented. Results are obtained by improving a recent approach to describe α\alpha preformation in 212^{212}Po [Phys. Rev. C 90, 034304 (2014)] implementing four-nucleon correlations (quartetting). Using the actually measured density distribution of the 208^{208} Pb core, the calculated alpha decay width of 212^{212}Po agrees fairly well with the measured one.Comment: 7 pages, 5 figures, 1 table, submitted to Phys. Rev.

    Bound clusters on top of doubly magic nuclei

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    An effective α\alpha particle equation is derived for cases where an α\alpha particle is formed on top of a doubly magic nucleus. As an example, we consider 212^{212}Po with the α\alpha on top of the 208^{208} Pb core. We will consider the core nucleus infinitely heavy, so that the α\alpha particle moves with respect to a fixed center, i.e., recoil effects are neglected. The fully quantal solution of the problem is discussed. The approach is inspired by the THSR (Tohsaki-Horiuchi-Schuck-R\"{o}pke) wave function concept that has been successfully applied to light nuclei. Shell model calculations are improved by including four-particle (α\alpha-like) correlations that are of relevance when the matter density becomes low. In the region where the α\alpha-like cluster penetrates the core nucleus, the intrinsic bound state wave function transforms at a critical density into an unbound four-nucleon shell model state. Exploratory calculations for 212^{212}Po are presented. Such preformed cluster states are only hardly described by shell model calculations. Reasons for different physics behavior of an α\alpha-like cluster with respect to a deuteron-like cluster are discussed.Comment: 24 pages, 5 figure

    Uniqueness of bounded solutions for the homogeneous Landau equation with a Coulomb potential

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    We prove the uniqueness of bounded solutions for the spatially homogeneous Fokker-Planck-Landau equation with a Coulomb potential. Since the local (in time) existence of such solutions has been proved by Arsen'ev-Peskov (1977), we deduce a local well-posedness result. The stability with respect to the initial condition is also checked
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