Nuclear Theory·nucl-th

Thursday·May 14, 2020

8 papers—4 primary·4 cross-listed

01
From odd-even staggering to the pairing gap in neutron matter
Georgios Palkanoglou · Fotis K. Diakonos · Alexandros Gezerlis
The properties of neutron matter are integral to the correct description of neutron stars as well as the description of neutron-rich nuclei. One key property of neutron matter is its superfluid behaviour in a range of densities relevant to the inner crust of neutron stars. This work investigates the finite-size effects in the pairing gap of a pure neutron matter superfluid system at densities found in the inner crust of cold neutron stars. The BCS (Bardeen-Cooper-Schrieffer) treatment of superfluidity gives rise to the mean-field pairing gap while a projection after variation (PBCS Theory) can provide a beyond-mean-field pairing gap through an odd-even staggering formula. While these two pairing gap results should agree in the thermodynamic limit, in this work we demonstrate that this is the case for systems far from the thermodynamic limit as well. This is a first step towards a model-independent extraction of the pairing gap in neutron matter.
nucl-thcond-mat.quant-gasPRC(2020)·9 citations
02
Nonlinear Fokker-Planck Acceleration for Forward-Peaked Transport Problems in Slab Geometry
J. J. Kuczek · J. K. Patel · R. Vasques
This paper introduces a nonlinear acceleration technique that accelerates the convergence of solution of transport problems with highly forward-peaked scattering. The technique is similar to a conventional high-order/low-order (HOLO) acceleration scheme. The Fokker-Planck equation, which is an asymptotic limit of the transport equation in highly forward-peaked settings, is modified and used for acceleration; this modified equation preserves the angular flux and moments of the (high order) transport equation. We present numerical results using the Screened Rutherford, Exponential, and Henyey-Greenstein scattering kernels and compare them to established acceleration methods such as diffusion synthetic acceleration (DSA). We observe three to four orders of magnitude speed-up in wall-clock time compared to DSA.
nucl-thcs.NAmath.NA0 citations
03
Coexistence of planar and aplanar rotations in $^{195}$ Tl
J. Peng🇨🇳 · Q. B. Chen🇩🇪
The chirality suggested for the doublet bands B2 and B2a in $^{195}$ Tl in $A \sim 190$ region is reexamined. The potential-energy curves and the configurations together with the deformation parameters are obtained by the constrained covariant density functional theory. The corresponding experimental energy spectra, energy differences between doublet bands, and the available $B (M 1) / B (E 2)$ values are investigated by the fully quantal particle rotor model. Analysis on the basis of the angular momentum components, the $K$ -plots, and the azimuthal plots suggest a planar rotation interpretation for the bands B2 and B2a. Hence, it coexists with the aplanar rotation in the other doublet bands B4 and B4a in $^{195}$ Tl.
nucl-thnucl-exPLB(2020)·14 citations
04
Symmetries Created by Random Interactions- Ultimacy of "More Is Different"
Takaharu Otsuka · Noritaka Shimizu
The dominance (preponderance) of the 0+ ground state for random interactions is shown to be a consequence of certain random interactions with chaotic features. These random interactions, called chaotic random interactions, impart a symmetry property to the ground-state wave function: an isotropy under an appropriate transformation, such as zero angular momentum for rotation. Under this mechanism, the ground-state parity and isospin can also be predicted in such a manner that positive parity is favored over negative parity and the isospin T = 0 is favored over higher isospins. As chaotic random interaction is a limit with no particular dynamics at the level of two interacting particles, this realization of isotropic symmetry in the ground state can be considered as the ultimate case of many-body correlations. A possible relation to the isotropy of the early universe is mentioned.
nucl-thnucl-exquant-ph0 citations
05
Connection between soft and hard probes of small collision systems at RHIC and LHC
Dennis V. Perepelitsa🇺🇸
The expected connections between signatures in the soft and hard sectors of small collision systems, and the status of experimental attempts to identify them, are discussed. These proceedings summarize the talk as given at the International Symposium on Multi-Particle Dynamics in September 2019 in Santa Fe, NM (ISMD19). As such, the choice of content and focus are selective and not intended to be comprehensive.
↳ nucl-exnucl-thEPJ Web Conf.(2020)·3 citations
06
On the inversion of isobaric-analogue states in nuclei
J. Henderson · S. R. Stroberg
Isospin is an approximate symmetry in atomic nuclei, arising from the rather similar properties of protons and neutrons. Perhaps the clearest manifestation of isospin within nuclei is in the near-identical structure of excited states in mirror nuclei: nuclei with inverted numbers of protons and neutrons. Isospin symmetry, and therefore mirror-symmetry, is broken by electromagnetic interactions and the difference in the masses of the up and down quarks. A recent study by Hoff and collaborators presented evidence that the ground-state spin of $^{73}$ Sr is different from that of its mirror, $^{73}$ Br, due to an inversion of the ground- and first-excited states, separated by only 27 keV in the $^{73}$ Br system. In this brief note, we place this inversion within the necessary context of the past half-century of experimental and theoretical work, and show that it is entirely consistent with normal behaviour, and affords no new insight into isospin-symmetry breaking. The essential point is that isospin-breaking effects due to the Coulomb interaction frequently vary from level to level within a given medium-mass nucleus by as much as 200 keV. Any level splitting smaller than this is liable to manifest a level inversion in the mirror partner which, absent disagreement with an appropriate nuclear model, does not challenge our understanding. While we note the novelty of an inversion in nuclear ground states, we emphasize that in the context of isospin there is nothing specifically illuminating about the ground state, or a level inversion.
↳ nucl-exnucl-thPRC(2020)·13 citations
07
Renormalization group and scattering-equivalent Hamiltonians on a coarse momentum grid
María Gómez-Rocha🇪🇸 · Enrique Ruiz Arriola🇪🇸
We consider the $π π$ -scattering problem in the context of the Kadyshevsky equation. In this scheme, we introduce a momentum grid and provide an isospectral definition of the phase-shift based on the spectral shift of a Chebyshev angle. We address the problem of the unnatural high momentum tails present in the fitted interactions which reaches energies far beyond the maximal center-of-mass energy of $s = 1.4$ GeV. It turns out that these tails can be integrated out by using a block-diagonal generator of the SRG.
↳ hep-phnucl-thActa Phys.Polon.Supp.(2021)·1 citation
08
Semileptonic decays $D \to π^{+} π^{-} e^{+} ν_{e}$ and $D_{s} \to π^{+} π^{-} e^{+} ν_{e}$ as the probe of constituent quark-antiquark pairs in the light scalar mesons
N.N. Achasov🇷🇺 · A.V. Kiselev🇷🇺 · G.N. Shestakov🇷🇺
Decays $D \to π^{+} π^{-} e^{+} ν_{e}$ and $D_{s} \to π^{+} π^{-} e^{+} ν_{e}$ serve as probes that check the existence of constituent $q q ˉ$ components in the wave functions of scalar mesons decaying into $π^{+} π^{-}$ . There exists a great deal of concrete evidence in favor of the exotic four-quark nature of light scalars. At the same time, the further expansion of the area of the $q^{2} q ˉ^{2}$ model validity for light scalars on ever new processes seems extremely interesting and important. We analyze the BESIII and CLEO data on the decays $D^{+} \to π^{+} π^{-} e^{+} ν_{e}$ and $D_{s}^{+} \to π^{+} π^{-} e^{+} ν_{e}$ and show that the results of these experiments together can be interpreted in favor of the four-quark nature of light scalar mesons $σ (500)$ and $f_{0} (980)$ . Our approach can also be applied to the description of other similar decays involving light scalars.
↳ hep-phhep-exnucl-thPRD(2020)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE