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Nuclear Theory·nucl-th

Wednesday·October 5, 2016

10 papers—7 primary·3 cross-listed

All10Primary7Cross-lists3
  1. 01

    Renormalisation Group Flow and Kaon Condensation

    Boris Krippa🇬🇧

    Functional renormalisation group approach is applied to a system of kaons with finite chemical potential. A set of approximate flow equations for the effective couplings is derived and solved. At high scale the system is found to be at the normal phase whereas at some critical value of the running scale it undergoes the phase transition (PT) to the phase with a spontaneously broken symmetry with the kaon condensate as an order parameter. The value of the condensate turns out to be quite sensitive to the kaon-kaon scattering length.

    nucl-thhep-phJ.Phys.G(2017)·0 citations
  2. 02

    A possible quantum fluid-dynamical approach to vortex motion in nuclei

    Seiya Nishiyama · Joao da Providencia

    The essential point of Bohr-Mottelson theory is to assume a irrotational flow. As was already suggested by Marumori and Watanabe, the internal rotational motion, i.e., the vortex motion, however, may exist also in nuclei. So, we have a necessity of taking the vortex motion into consideration. In a classical fluid dynamics, there are various ways to treat the internal rotational velocity. The Clebsch representation, v(x) = -\nabla \phi(x) + \lambda(x) \nabla \psi(x) (\phi ; velocity potential, \lambda and \psi: Clebsch parameters) is very powerful and has an advantage deriving equations of fluid motion from a Lagransian. Making the best use of the advantage, Kronig-Thellung, Ziman and Ito obtained a Hamiltonian including the internal rotational motion, the vortex motion, through the term \lambda(x) \nabla \psi(x). Going to quantum fluid dynamics, Ziman and Thellung finally derived a roton spectrum of liquid Helium II postulated by Landau. Is it possible to apply such the manner to a description of the collective vortex motion in nuclei? The description of such a collective motion has never been treated in the Bohr-Mottelson model (BMM) for a long time. In this paper, we will investigate a possibility of describing the vortex motion in nuclei basing on the theories of Ziman and Ito together with Marumori's work.

    nucl-thIJMPE(2017)·1 citation
  3. 03

    Permanent Electric Dipole Moments of Single-, Two-, and Three-Nucleon Systems

    Andreas Wirzba🇩🇪 · Jan Bsaisou🇩🇪 · Andreas Nogga🇺🇸

    A nonzero electric dipole moment (EDM) of the neutron, proton, deuteron or helion, in fact, of any finite system necessarily involves the breaking of a symmetry, either by the presence of external fields (i.e. electric fields leading to the case of induced EDMs) or explicitly by the breaking of the discrete parity and time-reflection symmetries in the case of permanent EDMs. We discuss two theorems describing these phenomena and report about the cosmological motivation for an existence of CP breaking beyond what is generated by the Kobayashi-Maskawa mechanism in the Standard Model and what this might imply for the permanent electric dipole moments of the nucleon and light nuclei by estimating a window of opportunity for physics beyond what is currently known. Recent - and in the case of the deuteron even unpublished - results for the relevant matrix elements of nuclear EDM operators are presented and the relevance for disentangling underlying New Physics sources are discussed.

    nucl-thhep-lathep-phquant-phIJMPE(2017)·13 citations
  4. 04

    The isospin dependent nucleon-nucleon inelastic cross section in the nuclear medium

    Qingfeng Li🇨🇳 · Zhuxia Li🇨🇳

    The calculation of the energy-, density-, and isospin-dependent production cross sections in nucleon-nucleon (NN) scattering has been performed within the framework of the relativistic BUU approach. The N cross sections are calculated in Born approximation taking into account the effective mass splitting of the nucleons and s in asymmetric matter. Due to the different mass splitting for neutron, proton and differently charged s, it is shown that, similar to the NN elastic ones, the reductions of N inelastic cross sections in isospin-asymmetric nuclear medium are different from each other for all the individual channels and the effect is largest and of opposite sign for the and states. This approach is also compared to calculations without effective mass splitting and with splitting derived from Dirac-Brueckerner (DB) calculations. The isospin dependence of the N cross sections is expected to influence the production of and mesons as well as their yield ratio, and thus affect the use of the latter quantity as a probe of the stiffness of the symmetry energy at supranormal densities.

    nucl-thPLB(2017)·31 citations
  5. 05

    Empirical parametrizations of the resonance amplitudes based on the Siegert's theorem

    G. Ramalho🇧🇷

    We present parametrizations of the , and transition amplitudes that are compatible with the analytic constraints at the pseudothreshold (Siegert's theorem). The presented parametrizations also provide a fair description of the experimental data. For the case of the transition, we discuss how the pion cloud parametrizations of the electric and the Coulomb quadrupole form factors can be adjusted according to the Siegert's theorem.

    nucl-thhep-exhep-phnucl-exJPS Conf.Proc.(2017)·0 citations
  6. 06

    Critical fluctuations in models with van der Waals interactions

    V. Vovchenko🇩🇪 · D. V. Anchishkin🇺🇦 · M. I. Gorenstein🇺🇦 · R. V. Poberezhnyuk🇺🇦 · H. Stoecker🇩🇪

    Particle number fluctuations are considered within the van der Waals (VDW) equation, which contains both attractive (mean-field) and repulsive (eigenvolume) interactions. The VDW equation is used to calculate the scaled variance of particle number fluctuations in generic Boltzmann VDW system and in nuclear matter. The strongly intensive measures and of the particle number and excitation energy fluctuations are also considered, and, similarly, show singular behavior near the critical point. The measure is shown to attain both positive and negative values in the vicinity of critical point. Based on universality argument, similar behavior is expected to occur in the vicinity of the QCD critical point.

    nucl-thhep-phActa Phys.Polon.Supp.(2017)·4 citations
  7. 07

    The N/D method with non-perturbative left-hand-cut discontinuity and the partial wave

    D.R. Entem🇪🇸 · J.A. Oller🇪🇸

    In this letter we deduce an integral equation that allows to calculate the exact left-hand-cut discontinuity for an uncoupled -wave partial-wave amplitude in potential scattering for a given finite-range potential. The results obtained from the method for the partial-wave amplitude are rigorous, since now the discontinuities along the left-hand cut and right-hand cut are exactly known. This solves the open question with respect to the method and the effect on the final result of the non-perturbative iterative diagrams in the evaluation of . A big advantage of the method is that short-range physics (corresponding to integrated out degrees of freedom within low-energy Effective Field Theory) does not contribute to and it manifests through the extra subtractions that are implemented within the method. We show the equivalence of the method and the Lippmann-Schwinger (LS) equation for a nonsingular potential (Yukawa potential). The equivalence between the method with one extra subtraction and the LS equation renormalized with one counter term or with subtractive renormalization also holds for the singular attractive higher-order ChPT potentials. The method also allows to evaluate partial-wave amplitudes with a higher number of extra subtractions, that we fix in terms of shape parameters within the effective range expansion. The result at NNLO shows that the phase shifts might be accurately described once the electromagnetic and charge symmetry breaking terms are included. Our present results can be extended to higher partial waves as well as to coupled channel scattering.

    nucl-thhep-phPLB(2017)·25 citations

Affiliations

first authorsco-authorsvia INSPIRE