Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Quantum Isomorphic Shell Model: Multi-Harmonic Shell Clustering of Nuclei  [PDF]
G. S. Anagnostatos
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.45B011
Abstract: The present multi-harmonic shell clustering of a nucleus is a direct consequence of the fermionic nature of nucleons and their average sizes. The most probable form and the average size for each proton or neutron shell are here presented by a specific equilibrium polyhedron of definite size. All such polyhedral shells are closely packed leading to a shell clustering of a nucleus. A harmonic oscillator potential is employed for each shell. All magic and semi-magic numbers, g.s. single particle and total binding energies, proton, neutron and mass radii of 40Ca, 48Ca, 54Fe, 90Zr, 108Sn, 114Te, 142Nd, and 208Pb are very successfully predicted.


Clustering aspects in nuclear structure functions  [PDF]
M. Hirai,S. Kumano,K. Saito,T. Watanabe
Physics , 2010, DOI: 10.1103/PhysRevC.83.035202
Abstract: For understanding an anomalous nuclear effect experimentally observed for the beryllium-9 nucleus at the Thomas Jefferson National Accelerator Facility (JLab), clustering aspects are studied in structure functions of deep inelastic lepton-nucleus scattering by using momentum distributions calculated in antisymmetrized (or fermionic) molecular dynamics (AMD) and also in a simple shell model for comparison. According to the AMD, the Be-9 nucleus consists of two alpha-like clusters with a surrounding neutron. The clustering produces high-momentum components in nuclear wave functions, which affects nuclear modifications of the structure functions. We investigated whether clustering features could appear in the structure function F_2 of Be-9 along with studies for other light nuclei. We found that nuclear modifications of F_2 are similar in both AMD and shell models within our simple convolution description although there are slight differences in Be-9. It indicates that the anomalous Be-9 result should be explained by a different mechanism from the nuclear binding and Fermi motion. If nuclear-modification slopes d(F_2^A/F_2^D)/dx are shown by the maximum local densities, the Be-9 anomaly can be explained by the AMD picture, namely by the clustering structure, whereas it certainly cannot be described in the simple shell model. This fact suggests that the large nuclear modification in Be-9 should be explained by large densities in the clusters. For example, internal nucleon structure could be modified in the high-density clusters. The clustering aspect of nuclear structure functions is an unexplored topic which is interesting for future investigations.
Clustering in stable and unstable nuclei in $p$-shell and $sd$-shell regions  [PDF]
Y. Kanada-En'yo,M. Kimura,H. Horiuchi
Physics , 2003, DOI: 10.1016/j.nuclphysa.2004.01.062
Abstract: According to microscopic calculations with antisymmetrized molecular dynamics, we studied cluster features in stable and unstable nuclei. A variety of structure was found in stable and unstable nuclei in the $p$-shell and $sd$-shell regions. The structure of excited states of $^{12}$Be was investigated, while in $sd$-shell nuclei we focused on molecular states and deformed states. The deformed states in $^{28}$Si and $^{40}$Ca were discussed in connection with the high-lying molecular states. Appealing molecular states in $^{36}$Ar and $^{24}$Mg were suggested. The results signified that both clustering of nucleons and mean-field formation are essential features in $sd$-shell nuclei as well as $p$-shell nuclei.
Aspects of Gravitational Clustering  [PDF]
T. Padmanabhan
Physics , 1999,
Abstract: Several issues related to the gravitational clustering of collisionless dark matter in an expanding universe is discussed. The discussion is pedagogical but the emphasis is on semianalytic methods and open questions - rather than on well established results.
Aspects of Scaling in Gravitational Clustering  [PDF]
Bhuvnesh Jain
Physics , 1995,
Abstract: The scaling ansatz of Hamilton et al. effectively extends the idea of self-similar scaling to initial power spectra of any generic shape. Applications of this ansatz have provided a semi-empirical analytical description of gravitational clustering which is extremely useful. This contribution examines the two theoretical ingredients that form the basis of these applications: self-similar evolution and the stable clustering hypothesis. A brief summary of work verifying self-similar scaling for scale free spectra $P(k) \propto k^n$, with $n < -1$ is given. The main results presented here examine the hypothesis that clustering is statistically stable in time on small scales, or equivalently that the mean pair velocity in physical coordinates is zero. The mean pair velocity of particles can be computed accurately from N-body simulations via the pair conservation equation, by using the evolution of the autocorrelation function $\xi(x,t)$. The results thus obtained for scale free spectra with $n = 0, -1, -2$ and for the CDM spectrum are consistent with the stable clustering prediction on the smallest resolved scales, on which the amplitude of $\xi \gsim 200-1000$ for $n = -2$ and $n = 0$, respectively.
Clustering effects for explaining an anomalous JLab result on the Be-9 structure function  [PDF]
M. Hirai,S. Kumano,K. Saito,T. Watanabe
Physics , 2011, DOI: 10.1063/1.3647423
Abstract: An anomalous nuclear modification was reported by JLab measurements on the beryllium-9 structure function F_2. It is unexpected in the sense that a nuclear modification slope is too large to be expected from its average nuclear density. We investigated whether it is explained by a nuclear clustering configuration in Be-9 with two \alpha nuclei and surrounding neutron clouds. Such clustering aspects are studied by using antisymmetrized molecular dynamics (AMD) and also by a simple shell model for comparison. We consider that nuclear structure functions F_2^A consist of a mean conventional part and a remaining one depending on the maximum local density. The first mean part does not show a significant cluster effect on F_2. However, we propose that the remaining one could explain the anonymous JLab slope, and it is associated with high densities created by the cluster formation in Be-9. The JLab measurement is possibly the first signature of clustering effects in high-energy nuclear reactions. A responsible physics could be an internal nucleon modification, which is caused by the high densities due to the cluster configuration.
An extrapolation method for shell model calculations  [PDF]
Takahiro Mizusaki,Masatoshi Imada
Physics , 2002, DOI: 10.1103/PhysRevC.65.064319
Abstract: We propose a new shell model method, combining the Lanczos digonalization and extrapolation method. This method can give accurate shell model energy from a series of shell model calculations with various truncation spaces, in a well-controlled manner. Its feasibility is demonstrated by taking the fp shell calculations.
Multi-Shell Shell Model for Heavy Nuclei  [PDF]
Yang Sun,Cheng-Li Wu
Physics , 2003, DOI: 10.1103/PhysRevC.68.024315
Abstract: Performing a shell model calculation for heavy nuclei has been a long-standing problem in nuclear physics. Here we propose one possible solution. The central idea of this proposal is to take the advantages of two existing models, the Projected Shell Model (PSM) and the Fermion Dynamical Symmetry Model (FDSM), to construct a multi-shell shell model. The PSM is an efficient method of coupling quasi-particle excitations to the high-spin rotational motion, whereas the FDSM contains a successful truncation scheme for the low-spin collective modes from the spherical to the well-deformed region. The new shell model is expected to describe simultaneously the single-particle and the low-lying collective excitations of all known types, yet keeping the model space tractable even for the heaviest nuclear systems.
An optimal shell model of turbulence  [PDF]
Victor S. L'vov,Evgenii Podivilov,Anna Pomyalov,Itamar Procaccia,Damien Vandembroucq
Physics , 1998, DOI: 10.1103/PhysRevE.58.1811
Abstract: We introduce a new shell model of turbulence which exhibits improved properties in comparison to the standard (and very popular) GOY model. The nonlinear coupling is chosen to minimize correlations between different shells. In particular the second order correlation function is diagonal in the shell index, the third order correlation exists only between three consecutive shells. Spurious oscillations in the scaling regime, which are an annoying feature of the GOY model, are eliminated by our choice of nonlinear coupling. We demonstrate that the model exhibits multi-scaling similarly to these GOY model. The scaling exponents are shown to be independent of the viscous mechanism as is expected for Navier-Stokes turbulence and other shell models. These properties of the new model make it optimal for further attempts to achieve understanding of multi-scaling in nonlinear dynamics.
No-Core Shell Model for Nuclear Systems with Strangeness  [PDF]
D. Gazda,J. Mare?,P. Navrátil,R. Roth,R. Wirth
Physics , 2013, DOI: 10.1007/s00601-014-0848-9
Abstract: We report on a novel ab initio approach for nuclear few- and many-body systems with strangeness. Recently, we developed a relevant no-core shell model technique which we successfully applied in first calculations of lightest $\Lambda$ hypernuclei. The use of a translationally invariant finite harmonic oscillator basis allows us to employ large model spaces, compared to traditional shell model calculations, and use realistic nucleon-nucleon and nucleon-hyperon interactions (such as those derived from EFT). We discuss formal aspects of the methodology, show first demonstrative results for ${}_{\Lambda}^3$H, ${}_{\Lambda}^4$H and ${}^4_\Lambda$He, and give outlook.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.