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T Otsuka - One of the best experts on this subject based on the ideXlab platform.
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Recent Shell-Model results for exotic nuclei
EPJ Web of Conferences, 2014Co-Authors: Yutaka Utsuno, M Honma, T Otsuka, Takahiro Mizusaki, Noritaka Shimizu, Yusuke Tsunoda, Takashi AbeAbstract:We report on our recent advancement in the Shell Model and its applications to exotic nuclei, focusing on the Shell evolution and large-scale calculations with the Monte Carlo Shell Model (MCSM). First, we test the validity of the monopole-based universal interaction (VMU) as a Shell-Model interaction by performing large-scale Shell- Model calculations in two di erent mass regions using e ective interactions which partly comprise VMU. Those calculations are successful and provide a deeper insight into the Shell evolution beyond the single-particle Model, in particular showing that the evolution of the spin-orbit splitting due to the tensor force plays a decisive role in the structure of the neutron-rich N 28 region and antimony isotopes. Next, we give a brief overview of recent developments in MCSM, and show that it is applicable to exotic nuclei that involve many valence orbits. As an example of its applications to exotic nuclei, shape coexistence in 32 Mg is examined.
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Shell Model results for exotic nuclei
The European Physical Journal A, 2003Co-Authors: T OtsukaAbstract:Recent developments of the nuclear Shell Model are presented. The magic numbers are the key concept of the Shell Model, and are shown to be different in exotic nuclei from those of stable nuclei. Their novel origin and robustness will be discussed. By the Monte Carlo Shell Model (MCSM), the structure of low-lying states can be studied with realistic interactions for a wide variety of nuclei. Some examples are discussed in connection to the triaxial deformation and a narrow Shell gap at N = 20 for Z smaller.
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Frontiers and challenges of nuclear Shell Model
European Physical Journal A, 2002Co-Authors: T Otsuka, M Honma, Yutaka Utsuno, Rintaro Fujimoto, B. A. Brown, Takahiro MizusakiAbstract:Two recent developments of the nuclear Shell Model are presented. One is a breakthrough in computational feasibility owing to the Monte Carlo Shell Model (MCSM). By the MCSM, the structure of low-lying states can be studied with realistic interactions for a wide, nearly unlimited basically, variety of nuclei. The magic numbers are the key concept of the Shell Model, and are shown to be different in exotic nuclei from those of stable nuclei. Its novel origin and robustness will be discussed.
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Monte Carlo Shell Model
Nuclear Physics, 2001Co-Authors: T OtsukaAbstract:Abstract The development and limitations of the conventional Shell-Model calculations are mentioned. In order to overcome the limitations, the Quantum Monte Carlo Diagonalization (QMCD) method has been proposed. The basic formulation and features of the QMCD method are presented as well as its application to the nuclear Shell Model, as referred to as Monte Carlo Shell Model (MCSM). The MCSM provides us with a breakthrough in the Shell-Model calculation: the structure of low-lying states can be studied with realistic interactions for a wide, nearly unlimited basically, variety of nuclei. Thus, the MCSM will contribute significantly to the physics to be developed by means of Radioactive Ion Beams. Applications to 56 Ni, Ba isotopes and N∼20 exotic nuclei far from the β stability line are mentioned.
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monte carlo Shell Model for atomic nuclei
Progress in Particle and Nuclear Physics, 2001Co-Authors: T Otsuka, M Honma, Takahiro Mizusaki, Yutaka UtsunoAbstract:The development, present status and future perspectives of the Monte Carlo Shell Model are discussed. The development and limitation of the conventional Shell Model calculations are shown, and stochastic approaches are introduced. As one of such approaches, the Quantum Monte Carlo Diagonalization (QMCD) method has been proposed. The formulation of the QMCD method is presented with an illustrative example. While the QMCD method is a general method for solving the quantum many-body interacting systems, its application to the nuclear Shell Model is referred to as the Monte Carlo Shell Model (MCSM). A test of the MCSM is presented, confirming the feasibility of the MCSM. The MCSM represents a breakthrough in Shell Model calculations: the level structure of low-lying states can be studied with realistic interactions for a wide, probably basically unlimited, variety of nuclei. The MCSM has two major characteristic features: the feasibility of including many single-particle orbits and the capability of handling many valence nucleons. We present some applications for which these features played essential roles. Such applications include the structure of exotic nuclei around the neutron number 20, a unified description of spherical to superdeformed states in nuclei around 56Ni, a new effective interaction for pf-Shell nuclei and their unified description, and microscopic studies on the spherical-deformed shape phase transition and on the γ-unstable deformation.
Alfredo Poves - One of the best experts on this subject based on the ideXlab platform.
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Deformation and superdeformation: The Shell Model way
Nuclear Physics A, 2004Co-Authors: Alfredo PovesAbstract:Abstract Present large scale Shell Model calculations give a very accurate and comprehensive description of light and medium light nuclei. Full pf -Shell calculations have made it possible to describe many collective features in an spherical Shell Model context. Calculations including two major oscillator Shells can cope with superdeformed bands. The underlying symmetries are seen to be variants of Elliott's SU3.
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New developments of the nuclear Shell Model
AIP Conference Proceedings, 2002Co-Authors: Alfredo PovesAbstract:More than fifty years ago, the independent particle Model of the nucleus was proposed by M. Goeppert-Mayer and H. Jensen. The label “Shell Model” has since changed meaning and nowadays it applies mainly to the description of the nucleus that results of the mixing of many Slater determinants by an effective “in medium” interaction, usually limited to one and two-body terms. The advent of efficient new algorithms to solve the secular problem, together with the increase in speed and storage capacity of modern computers, has brought into the reach of large scale Shell Model calculations entire regions of nuclei and of nuclear phenomena traditionally considered to be out of the Shell Model realm. This enormous extension of its field of practical applications has occurred simultaneously with a regain of experimental interest in the nuclear spectroscopy, in particular in very neutron rich and N=Z nuclei. The Shell Model work in large Model spaces demands a very complete understanding of the effective nuclear int...
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The nuclear Shell Model
An Advanced Course in Modern Nuclear Physics, 2001Co-Authors: Alfredo Poves, F. NowackiAbstract:In this series of lectures we discuss the basic notions of the spherical Shell Model. Starting from a regularized nucleon-nucleon interaction, we define the Model as an approximation to the exact solution of the full secular problem. We introduce the notions of valence space, effective interaction and effective operator. We analyse the structure of the realistic effective interactions, identifying their monopole part with the spherical mean field. The multipole hamiltonian is shown to have a simple and universal form that includes pairing (isovector and isoscalar), quadrupole, octupole, hexadecapole and (σ · τ) (σ · τ). We describe the methods of resolution of the secular problem, in particular the Lanczos method. Finally, we present some results on two different open problems in nuclear structure; the quenching of the strength of the spin operators in the nuclear medium and the spherical Shell Model description of deformation and superdeformation.
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Shell Model studies of neutron rich nuclei
Nuclear Physics A, 2001Co-Authors: Etienne Caurier, F. Nowacki, Alfredo PovesAbstract:We discuss the present status of the description of the structure of the very neutron rich nuclei, in the framework of modern large scale Shell Model calculations. Particular attention is paid to the interaction related issues, as well as to the problems of the Shell Model approach at the neutron drip line. We present detailed results for nuclei around N=20 and, more briefly, we discuss some salient features of the regions close to N=8, 28 and 40. We show that most experimental features can be understood in a Shell Model context.
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Spherical Shell Model, a renewed view
Response of the Nuclear System to External Forces, 1Co-Authors: Alfredo PovesAbstract:In these lectures the foundations of the spherical Shell Model description of nuclei are presented with particular emphasis in the relationship between spectroscopic and global properties. Non standard applications of the spherical Shell Model — to nuclei far from stability and to rotational motion — are explicitly discussed.
Yang Sun - One of the best experts on this subject based on the ideXlab platform.
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MULTI-MAJOR-Shell Shell Model FOR HEAVY NUCLEI–AN EXTENDED PROJECTED Shell Model
International Journal of Modern Physics E, 2008Co-Authors: Yang SunAbstract:The projected Shell Model (PSM) in its original version is an efficient Shell Model truncation scheme for well deformed nuclei. However, the Model is applicable only to rotational motion, but not collective vibrations. In this paper, we discuss a scheme that extends the PSM applicability to low-lying rotational and vibrational states possibly in all kinds of heavy nuclei (from deformed via transitional to spherical), thus rendering it to be a more general multi-major-Shell Shell Model for heavy nuclei. Three known types of vibration (β, γ, and scissors-mode) are discussed.
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MultiShell Shell Model for heavy nuclei
Physical Review C, 2003Co-Authors: Yang SunAbstract: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 combine the advantages of two existing Models, the projected Shell Model (PSM) and the fermion dynamical symmetry Model (FDSM), to construct a multiShell Shell Model. The PSM is an efficient method of coupling quasiparticle 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.
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The projected Shell Model
Journal of Physics G: Nuclear and Particle Physics, 1999Co-Authors: Víctor Velázquez, Jorge G. Hirsch, Yang SunAbstract:The projected Shell Model (PSM) provides a Shell Model treatment of heavy nuclei, through diagonalization of a pairing plus quadrupole Hamiltonian in an angular momentum projected zero-, two-, and four-quasiparticle basis (for even-even systems). Calculated energy levels and electromagnetic transition amplitudes are in good agreement with the experimental data. Taking as an example, we exhibit the effect of changing the residual interaction strengths on the spectra. It is clearly seen that there are many bandheads whose energies can only be reproduced using the self-consistent strengths. It is concluded that there are no free parameters in the PSM.
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Self-consistency in the Projected Shell Model
Nuclear Physics A, 1998Co-Authors: Víctor Velázquez, Jorge G. Hirsch, Yang SunAbstract:The Projected Shell Model is a Shell Model theory built up over a deformed BCS mean field. Ground state and excited bands in even-even nuclei are obtained through diagonalization of a pairing plus quadrupole Hamiltonian in an angular momentum projected 0-, 2-, and 4-quasiparticle basis. The residual quadrupole-quadrupole interaction strength is fixed self-consistently with the deformed mean field and the pairing constants are the same used in constructing the quasiparticle basis. Taking $^{160}Dy$ as an example, we calculate low-lying states and compare them with experimental data. We exhibit the effect of changing the residual interaction strengths on the spectra. It is clearly seen that there are many $J^\pi = 0^+, 1^+, 4^+$ bandheads whose energies can only be reproduced using the self-consistent strengths. It is thus concluded that the Projected Shell Model is a Model essentially with no free parameters.
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Fortran code of the Projected Shell Model: feasible Shell Model calculations for heavy nuclei
Computer Physics Communications, 1997Co-Authors: Yang Sun, Kenji HaraAbstract:Abstract A Fortran program is presented which conforms with the framework of the Projected Shell Model. The theory is a genuine Shell Model configuration mixing approach but requires only a very small configuration space. This feature enables us to interpret numerical results in simple physical terms. The present code allows detailed spectroscopic calculations for low- and high-spin states in axially deformed nuclei. It is written using a very efficient algorithm published earlier and runs extremely fast not only on Mainframes but also on Workstations or even on modern PCs.
F. Nowacki - One of the best experts on this subject based on the ideXlab platform.
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Shell Model half lives for r process n 82 nuclei
arXiv: Astrophysics, 2008Co-Authors: J J Cuencagarcia, F. Nowacki, G Martinezpinedo, K Langanke, I N BorzovAbstract:We have performed Shell-Model calculations of the half-lives and neutron-branching probabilities of the r-process waiting point nuclei at the magic neutron number N=82. These new calculations use a larger Model space than previous Shell Model studies and an improved residual interaction which is adjusted to recent spectroscopic data around A=130. Our Shell-Model results give a good account of all experimentally known half-lives and $Q_\beta$-values for the N=82 r-process waiting point nuclei. Our half-life predictions for the N=82 nuclei with Z=42--46 agree well with recent estimates based in the energy-density functional method.
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Shell Model half lives for r process n 82 nuclei
European Physical Journal A, 2007Co-Authors: J J Cuencagarcia, F. Nowacki, G Martinezpinedo, K Langanke, I N BorzovAbstract:We have performed Shell Model calculations of the half-lives and neutron-branching probabilities of the r-process waiting-point nuclei at the magic neutron number N = 82 . These new calculations use a larger Model space than previous Shell Model studies and an improved residual interaction which is adjusted to recent spectroscopic data around A = 130 . Our Shell Model results give a good account of all experimentally known half-lives and Q β -values for the N = 82 r-process waiting-point nuclei. Our half-life predictions for the N = 82 nuclei with Z = 42-46 agree well with recent estimates based in the energy-density functional method.
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Shell Model half-lives for r-process N = 82 nuclei
European Physical Journal A, 2007Co-Authors: J.j. Cuenca-garcıa, F. Nowacki, K Langanke, G. Martınez-pinedo, I N BorzovAbstract:We have performed Shell Model calculations of the half-lives and neutron-branching probabilities of the r-process waiting-point nuclei at the magic neutron number N = 82. These new calculations use a larger Model space than previous Shell Model studies and an improved residual interaction which is adjusted to recent spectroscopic data around A = 130. Our Shell Model results give a good account of all experimentally known half-lives and $Q_\beta^-$ values for the N = 82 r-process waiting-point nuclei. Our half-life predictions for the N = 82 nuclei with Z = 42-46 agree well with recent estimates based in the energy-density functional method.
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The nuclear Shell Model
An Advanced Course in Modern Nuclear Physics, 2001Co-Authors: Alfredo Poves, F. NowackiAbstract:In this series of lectures we discuss the basic notions of the spherical Shell Model. Starting from a regularized nucleon-nucleon interaction, we define the Model as an approximation to the exact solution of the full secular problem. We introduce the notions of valence space, effective interaction and effective operator. We analyse the structure of the realistic effective interactions, identifying their monopole part with the spherical mean field. The multipole hamiltonian is shown to have a simple and universal form that includes pairing (isovector and isoscalar), quadrupole, octupole, hexadecapole and (σ · τ) (σ · τ). We describe the methods of resolution of the secular problem, in particular the Lanczos method. Finally, we present some results on two different open problems in nuclear structure; the quenching of the strength of the spin operators in the nuclear medium and the spherical Shell Model description of deformation and superdeformation.
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Shell Model studies of neutron rich nuclei
Nuclear Physics A, 2001Co-Authors: Etienne Caurier, F. Nowacki, Alfredo PovesAbstract:We discuss the present status of the description of the structure of the very neutron rich nuclei, in the framework of modern large scale Shell Model calculations. Particular attention is paid to the interaction related issues, as well as to the problems of the Shell Model approach at the neutron drip line. We present detailed results for nuclei around N=20 and, more briefly, we discuss some salient features of the regions close to N=8, 28 and 40. We show that most experimental features can be understood in a Shell Model context.
Yutaka Utsuno - One of the best experts on this subject based on the ideXlab platform.
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Recent Shell-Model results for exotic nuclei
EPJ Web of Conferences, 2014Co-Authors: Yutaka Utsuno, M Honma, T Otsuka, Takahiro Mizusaki, Noritaka Shimizu, Yusuke Tsunoda, Takashi AbeAbstract:We report on our recent advancement in the Shell Model and its applications to exotic nuclei, focusing on the Shell evolution and large-scale calculations with the Monte Carlo Shell Model (MCSM). First, we test the validity of the monopole-based universal interaction (VMU) as a Shell-Model interaction by performing large-scale Shell- Model calculations in two di erent mass regions using e ective interactions which partly comprise VMU. Those calculations are successful and provide a deeper insight into the Shell evolution beyond the single-particle Model, in particular showing that the evolution of the spin-orbit splitting due to the tensor force plays a decisive role in the structure of the neutron-rich N 28 region and antimony isotopes. Next, we give a brief overview of recent developments in MCSM, and show that it is applicable to exotic nuclei that involve many valence orbits. As an example of its applications to exotic nuclei, shape coexistence in 32 Mg is examined.
-
Frontiers and challenges of nuclear Shell Model
European Physical Journal A, 2002Co-Authors: T Otsuka, M Honma, Yutaka Utsuno, Rintaro Fujimoto, B. A. Brown, Takahiro MizusakiAbstract:Two recent developments of the nuclear Shell Model are presented. One is a breakthrough in computational feasibility owing to the Monte Carlo Shell Model (MCSM). By the MCSM, the structure of low-lying states can be studied with realistic interactions for a wide, nearly unlimited basically, variety of nuclei. The magic numbers are the key concept of the Shell Model, and are shown to be different in exotic nuclei from those of stable nuclei. Its novel origin and robustness will be discussed.
-
monte carlo Shell Model for atomic nuclei
Progress in Particle and Nuclear Physics, 2001Co-Authors: T Otsuka, M Honma, Takahiro Mizusaki, Yutaka UtsunoAbstract:The development, present status and future perspectives of the Monte Carlo Shell Model are discussed. The development and limitation of the conventional Shell Model calculations are shown, and stochastic approaches are introduced. As one of such approaches, the Quantum Monte Carlo Diagonalization (QMCD) method has been proposed. The formulation of the QMCD method is presented with an illustrative example. While the QMCD method is a general method for solving the quantum many-body interacting systems, its application to the nuclear Shell Model is referred to as the Monte Carlo Shell Model (MCSM). A test of the MCSM is presented, confirming the feasibility of the MCSM. The MCSM represents a breakthrough in Shell Model calculations: the level structure of low-lying states can be studied with realistic interactions for a wide, probably basically unlimited, variety of nuclei. The MCSM has two major characteristic features: the feasibility of including many single-particle orbits and the capability of handling many valence nucleons. We present some applications for which these features played essential roles. Such applications include the structure of exotic nuclei around the neutron number 20, a unified description of spherical to superdeformed states in nuclei around 56Ni, a new effective interaction for pf-Shell nuclei and their unified description, and microscopic studies on the spherical-deformed shape phase transition and on the γ-unstable deformation.
