Nuclear Theory·nucl-th

Wednesday·October 5, 2016

10 papers—7 primary·3 cross-listed

01
[Submitted on 3 Oct 2016]
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.
Comments:
8 pages, 3 figures, updated version accepted for publication
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1610.00744 [pdf]
J.Phys.G(2017)·0 citations
02
[Submitted on 3 Oct 2016]
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.
Comments:
23 pages, no figures, Publication version
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1610.00793 [pdf]
IJMPE(2017)·1 citation
03
[Submitted on 3 Oct 2016]
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.
Comments:
20 pages, chapter for the memorial book "Gerry Brown 90", final version, some typos corrected
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Quantum Physics (quant-ph)
arXiv:
1610.00794 [pdf]
IJMPE(2017)·13 citations
04
[Submitted on 4 Oct 2016]
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 $Δ$ production cross sections in nucleon-nucleon (NN) scattering $σ_{N N \to N Δ}^{*}$ has been performed within the framework of the relativistic BUU approach. The N $Δ$ cross sections are calculated in Born approximation taking into account the effective mass splitting of the nucleons and $Δ$ s in asymmetric matter. Due to the different mass splitting for neutron, proton and differently charged $Δ$ s, it is shown that, similar to the NN elastic ones, the reductions of N $Δ$ 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 $Δ^{++}$ and $Δ^{-}$ 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 $Δ$ cross sections is expected to influence the production of $π^{+}$ and $π^{-}$ 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.
Comments:
17 pages including 4 figures. Accepted by Phys. Lett. B
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1610.00827 [pdf]
PLB(2017)·31 citations
05
[Submitted on 3 Oct 2016]
Empirical parametrizations of the resonance amplitudes based on the Siegert's theorem
G. Ramalho🇧🇷
We present parametrizations of the $γ^{*} N \to N (1535) 1/ 2^{-}$ , $γ^{*} N \to N (1520) 3/ 2^{-}$ and $γ^{*} N \to Δ (1232) 3/ 2^{+}$ 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 $γ^{*} N \to Δ (1232) 3/ 2^{+}$ 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.
Comments:
Proceedings of the "The 14th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon". July 25-30, 2016, Kyoto, Japan. 5 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1610.01017 [pdf]
JPS Conf.Proc.(2017)·0 citations
06
[Submitted on 4 Oct 2016]
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 $Δ [E^{*}, N]$ and $Σ [E^{*}, N]$ of the particle number and excitation energy fluctuations are also considered, and, similarly, show singular behavior near the critical point. The $Δ [E^{*}, N]$ 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.
Comments:
5 pages, 2 figures. Contribution to the proceedings of the Critical Point and Onset of Deconfinement 2016, Wroclaw, Poland, May 30th - June 4th, 2016
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1610.01036 [pdf]
Acta Phys.Polon.Supp.(2017)·4 citations
07
[Submitted on 4 Oct 2016]
The N/D method with non-perturbative left-hand-cut discontinuity and the $^{1} S_{0}$ $N N$ 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 $S$ -wave partial-wave amplitude in potential scattering for a given finite-range potential. The results obtained from the $N / D$ 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 $N / D$ method and the effect on the final result of the non-perturbative iterative diagrams in the evaluation of $Δ (A)$ . 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 $Δ (A)$ and it manifests through the extra subtractions that are implemented within the method. We show the equivalence of the $N / D$ method and the Lippmann-Schwinger (LS) equation for a nonsingular $^{1} S_{0}$ $N N$ potential (Yukawa potential). The equivalence between the $N / D$ 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 $N / D$ 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 $^{1} S_{0}$ 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.
Comments:
7 pages, 1 table and 7 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1610.01040 [pdf]
PLB(2017)·25 citations
08
[Submitted on 2 Oct 2016] (cross-list from hep-lat)
Probing the nature of phases across the phase transition at finite isospin chemical potential
Gunnar S. Bali🇩🇪 · G. Endrodi🇩🇪 · Rajiv V. Gavai🇮🇳 · N. Mathur🇮🇳
We compare the low eigenvalue spectra of the Overlap Dirac operator on two sets of configurations at $μ_{I} / μ_{I}^{c}$ = 0.5 and 1.5 generated with dynamical staggered fermions at these isospin chemical potential on $2 4^{3} \times 6$ lattices. We find very small changes in the number of zero modes and low lying modes which is in stark contrast with those across the corresponding finite temperature phases where one sees a drop across the phase transition. Possible consequences are discussed.
Comments:
6 Pages, 3 Figures, Submitted for the proceedings of the 10th International Conference on Critical Point and Onset of Deconfinement (CPOD 2016), Wroclaw, Poland
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1610.00233 [pdf]
Acta Phys.Polon.Supp.(2017)·6 citations
09
[Submitted on 4 Oct 2016] (cross-list from math.NA)
A fast algorithm for radiative transport in isotropic media
Kui Ren · Rongting Zhang · Yimin Zhong
We propose in this work a fast numerical algorithm for solving the equation of radiative transfer (ERT) in isotropic media. The algorithm has two steps. In the first step, we derive an integral equation for the angularly averaged ERT solution by taking advantage of the isotropy of the scattering kernel, and solve the integral equation with a fast multipole method (FMM). In the second step, we solve a scattering-free transport equation to recover the original ERT solution. Numerical simulations are presented to demonstrate the performance of the algorithm for both homogeneous and inhomogeneous media.
Subjects:
math.NA (math.NA); cs.NA (cs.NA); Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
arXiv:
1610.00835 [pdf]
J.Comput.Phys.(2019)·0 citations
10
[Submitted on 4 Oct 2016] (cross-list from astro-ph.HE)
Equation of State for Nucleonic and Hyperonic Neutron Stars with Mass and Radius Constraints
Laura Tolos🇪🇸 · Mario Centelles🇪🇸 · Angels Ramos🇪🇸
We obtain a new equation of state for the nucleonic and hyperonic inner core of neutron stars that fulfills the 2 $M_{⊙}$ observations as well as the recent determinations of stellar radii below 13 km. The nucleonic equation of state is obtained from a new parametrization of the FSU2 relativistic mean-field functional that satisfies these latest astrophysical constraints and, at the same time, reproduces the properties of nuclear matter and finite nuclei while fulfilling the restrictions on high-density matter deduced from heavy-ion collisions. On the one hand, the equation of state of neutron star matter is softened around saturation density, which increases the compactness of canonical neutron stars leading to stellar radii below 13 km. On the other hand, the equation of state is stiff enough at higher densities to fulfill the 2 $M_{⊙}$ limit. By a slight modification of the parametrization, we also find that the constraints of 2 $M_{⊙}$ neutron stars with radii around 13 km are satisfied when hyperons are considered. The inclusion of the high magnetic fields present in magnetars further stiffens the equation of state. Hyperonic magnetars with magnetic fields in the surface of $\sim 1 0^{15}$ G and with values of $\sim 1 0^{18}$ G in the interior can reach maximum masses of 2 $M_{⊙}$ with radii in the 12-13 km range.
Comments:
18 pages, 9 figures, 2 tables, accepted for publication in The Astrophysical Journal
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1610.00919 [pdf]
ApJ(2017)·135 citations

Affiliations

first authorsco-authorsvia INSPIRE