Updated on 2024/07/17

写真a

 
TAKANO, Masatoshi
 
Affiliation
Faculty of Science and Engineering, School of Advanced Science and Engineering
Job title
Professor
Degree
理学博士
(BLANK)
博士(理学) ( 早稲田大学 )

Education Background

  •  
    -
    1994

    Waseda University   Graduate School, Division of Science and Engineering  

  •  
    -
    1989

    Waseda University   Faculty of Science and Engineering  

Professional Memberships

  •  
     
     

    アメリカ物理学会

  •  
     
     

    日本物理学会

Research Areas

  • Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics

Research Interests

  • Elementary Particles Physics,Nuclear Physics & Cosmic Ray Physics

 

Papers

  • Effects of finite sizes of atomic nuclei on shear modulus and torsional oscillations in neutron stars

    H. Sotani, H. Togashi, M. Takano

    Monthly Notices of the Royal Astronomical Society   516 ( 4 ) 5440 - 5445  2022.11  [Refereed]

     View Summary

    ABSTRACT

    The shear modulus of neutron star matter is one of the important properties used for determining torsional oscillations in neutron stars. We take into account the effects of finite sizes of spherical nuclei on the shear modulus and examine the frequencies of crustal torsional oscillations. The shear modulus decreases owing to the finite-size effect, which in turn decreases the frequencies of torsional oscillations. In particular, the finite-size effect becomes more crucial for oscillations with a larger azimuthal quantum number and for neutron star models with a weaker density dependence of nuclear symmetry energy. In practice, when one identifies quasi-periodic oscillations from a neutron star, where magnetic effects are negligible, with crustal torsional oscillations, the finite-size effect can be more significant at frequencies higher than ∼100 Hz.

    DOI

    Scopus

    4
    Citation
    (Scopus)
  • 中性子星は三体力が際立った「巨大な原子核」か

    飯田圭, 鷹野正利, 田島裕之

    科学   92 ( 10 ) 931 - 936  2022.10  [Invited]

  • Cluster Variational Method for Hyperonic Nuclear Matter with Coupled Channels

    H. Togashi, M. Takano

    JPS Conf. Proc.   26   031024  2019.11  [Refereed]

    DOI

  • New Table of Supernova Equation of State Using a Variational Method and Its Application to Astrophysical Compact Objects

    H. Togashi, K. Nakazato, Y. Takehara, S. Yamamuro, H. Suzuki, M. Takano

    JPS Conf. Proc.   20   011021-1 - 011021-5  2018  [Refereed]

    DOI

  • A new equation of state for core-collapse supernovae based on realistic nuclear forces and including a full nuclear ensemble

    S. Furusawa, H. Togashi, H. Nagakura, K. Sumiyoshi, S. Yamada, H. Suzuki, M. Takano

    JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS   44 ( 9 ) 094001  2017.09  [Refereed]

     View Summary

    We have constructed a nuclear equation of state (EOS) that includes a full nuclear ensemble for use in core-collapse supernova simulations. It is based on the EOS for uniform nuclear matter that two of the authors derived recently, applying a variational method to realistic two-and three-body nuclear forces. We have extended the liquid drop model of heavy nuclei, utilizing the mass formula that accounts for the dependences of bulk, surface, Coulomb and shell energies on density and/or temperature. As for light nuclei, we employ a quantum-theoretical mass evaluation, which incorporates the Pauli -and self-energy shifts. In addition to realistic nuclear forces, the inclusion of in-medium effects on the full ensemble of nuclei makes the new EOS one of the most realistic EOSs, which covers a wide range of density, temperature and proton fraction that supernova simulations normally encounter. We make comparisons with the FYSS EOS, which is based on the same formulation for the nuclear ensemble but adopts the relativistic mean field theory with the TM1 parameter set for uniform nuclear matter. The new EOS is softer than the FYSS EOS around and above nuclear saturation densities. We find that neutron-rich nuclei with small mass numbers are more abundant in the new EOS than in the FYSS EOS because of the larger saturation densities and smaller symmetry energy of nuclei in the former. We apply the two EOSs to 1D supernova simulations and find that the new EOS gives lower electron fractions and higher temperatures in the collapse phase owing to the smaller symmetry energy. As a result, the inner core has smaller masses for the new EOS. It is more compact, on the other hand, due to the softness of the new EOS and bounces at higher densities. It turns out that the shock wave generated by core bounce is a bit stronger initially in the simulation with the new EOS. The ensuing outward propagations of the shock wave in the outer core are very similar in the two simulations, which may be an artifact, though, caused by the use of the same tabulated electron capture rates for heavy nuclei ignoring differences in the nuclear composition between the two EOSs in these computations.

    DOI

    Scopus

    55
    Citation
    (Scopus)
  • Nuclear equation of state for core-collapse supernova simulations with realistic nuclear forces

    H. Togashi, K. Nakazato, Y. Takehara, S. Yamamuro, H. Suzuki, M. Takano

    NUCLEAR PHYSICS A   961   78 - 105  2017.05  [Refereed]

     View Summary

    A new table of the nuclear equation of state (EOS) based on realistic nuclear potentials is constructed for core-collapse supernova numerical simulations. Adopting the EOS of uniform nuclear matter constructed by two of the present authors with the cluster variational method starting from the Argonne v18 and Urbana IX nuclear potentials, the Thomas Fermi calculation is performed to obtain the minimized free energy of a Wigner-Seitz cell in non-uniform nuclear matter. As a preparation for the Thomas Fermi calculation, the EOS of uniform nuclear matter is modified so as to remove the effects of deuteron cluster formation in uniform matter at low densities. Mixing of alpha particles is also taken into account following the procedure used by Shen et al. (1998, 2011). The critical densities with respect to the phase transition from non-uniform to uniform phase with the present EOS are slightly higher than those with the Shen EOS at small proton fractions. The critical temperature with respect to the liquid gas phase transition decreases with the proton fraction in a more gradual manner than in the Shen EOS. Furthermore, the mass and proton numbers of nuclides appearing in non-uniform nuclear matter with small proton fractions are larger than those of the Shen EOS. These results are consequences of the fact that the density derivative coefficient of the symmetry energy of our EOS is smaller than that of the Shen EOS. (C) 2017 Elsevier B.V. All rights reserved.

    DOI

    Scopus

    135
    Citation
    (Scopus)
  • Variational study of the supernova equation of state with hyperons

    H. Togahi, E. Hiyama, M. Takano

    JPS Conf. Proc.   14   020812  2017  [Refereed]

  • Variational approach to neutron star matter with hyperons

    H. Togahi, E. Hiyama, Y. Yamamoto, M. Takano

    JPS Conf. Proc.   17   102002  2017  [Refereed]

    DOI

  • Equation of state of hyperonic nuclear matter at zero and finite temperatures with the variational method

    H. Togashi, E. Hiyama, M. Takano

    JPS Conf. Proc   18   011028  2017  [Refereed]

  • Equation of state for neutron stars with hyperons using a variational method

    H. Togashi, E. Hiyama, Y. Yamamoto, M. Takano

    PHYSICAL REVIEW C   93 ( 3 )  2016.03  [Refereed]

     View Summary

    We investigate the effects of the odd-state part of bare Lambda Lambda interactions on the structure of neutron stars (NSs) by constructing equations of state (EOSs) for uniform nuclear matter containing Lambda and Sigma(-) hyperons with use of the cluster variational method. The isoscalar part of the Argonne v18 two-nucleon potential and the Urbana IX three-nucleon potential are employed as the interactions between nucleons, whereas, as the bare Lambda N and even-state Lambda Lambda interactions, two-body central potentials that are determined so as to reproduce the experimental data on single-and double-Lambda hypernuclei are adopted. In addition, the Sigma(-) N interaction is constructed so as to reproduce the empirical single-particle potential of Sigma(-) in symmetric nuclear matter. Since the odd-state part of the Lambda Lambda interaction is not known owing to lack of experimental data, we construct four EOSs of hyperonic nuclear matter, each with a different odd-state part of the Lambda Lambda interaction. The EOS obtained for NS matter becomes stiffer as the odd-state Lambda Lambda interaction becomes more repulsive, and correspondingly the maximum mass of NSs increases. It is interesting that the onset density of Sigma(-) depends strongly on the repulsion of the odd-state Lambda Lambda interaction. Furthermore, we take into account the three-baryon repulsive force to obtain results that are consistent with observational data on heavy NSs.

    DOI

    Scopus

    35
    Citation
    (Scopus)
  • Equation of state for neutron stars with hyperons using a variational method

    H. Togashi, E. Hiyama, Y. Yamamoto, M. Takano

    Physical Review C - Nuclear Physics   93 ( 3 )  2016.03  [Refereed]

     View Summary

    © 2016 American Physical Society. We investigate the effects of the odd-state part of bare ΛΛ interactions on the structure of neutron stars (NSs) by constructing equations of state (EOSs) for uniform nuclear matter containing Λ and Σ- hyperons with use of the cluster variational method. The isoscalar part of the Argonne v18 two-nucleon potential and the Urbana IX three-nucleon potential are employed as the interactions between nucleons, whereas, as the bare ΛN and even-state ΛΛ interactions, two-body central potentials that are determined so as to reproduce the experimental data on single- and double-Λ hypernuclei are adopted. In addition, the Σ-N interaction is constructed so as to reproduce the empirical single-particle potential of Σ- in symmetric nuclear matter. Since the odd-state part of the ΛΛ interaction is not known owing to lack of experimental data, we construct four EOSs of hyperonic nuclear matter, each with a different odd-state part of the ΛΛ interaction. The EOS obtained for NS matter becomes stiffer as the odd-state ΛΛ interaction becomes more repulsive, and correspondingly the maximum mass of NSs increases. It is interesting that the onset density of Σ- depends strongly on the repulsion of the odd-state ΛΛ interaction. Furthermore, we take into account the three-baryon repulsive force to obtain results that are consistent with observational data on heavy NSs.

    DOI

    Scopus

    35
    Citation
    (Scopus)
  • 三体核力と中性子星(原子核物理用語・キーワード解説)

    鷹野正利

    原子核研究   60 ( 2 ) 20 - 21  2016.03  [Refereed]

  • Variational calculations with explicit energy functionals for fermion systems at zero temperature

    M. Takano, T. Suzuki, N. Sakumichi

    18TH INTERNATIONAL CONFERENCE ON RECENT PROGRESS IN MANY-BODY THEORIES (MBT18)   702   012016  2016  [Refereed]

     View Summary

    The variational method with explicit energy functionals (EEFs) is applied to infinite neutron matter. Starting from the Argonne v8' two-body potential and the repulsive part of the Urbana IX three-body potential, the energy per neutron is expressed explicitly with the spin-dependent central, tensor, and spin-orbit distribution functions. This EEF is constructed as an extension of the previously proposed one for the Argonne v6' potential, including central and tensor forces. The Euler-Lagrange equations derived from this EEF are solved numerically. The obtained fully minimized energy with this EEF is in good agreement with that obtained from the auxiliary field diffusion Monte Carlo calculation.

    DOI

    Scopus

  • エネルギー汎関数を用いた変分法による核物質状態方程式の研究

    鷹野正利

    素粒子論研究・電子版   22 ( 1 ) 98 - 100  2016.01

  • Application of the nuclear equation of state obtained by the variational method to core-collapse supernovae

    H. Togashi, M. Takano, K. Sumiyoshi, K. Nakazato

    PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS   023D05 ( 2 )  2014.02  [Refereed]

     View Summary

    The equation of state (EOS) for hot asymmetric nuclear matter that is constructed with the variational method starting from the Argonne v18 and Urbana IX nuclear forces is applied to spherically symmetric core-collapse supernovae (SNe). We first investigate the EOS of isentropic beta-stable SN matter, and find that matter with the variational EOS is more neutron-rich than that with the Shen EOS. Using the variational EOS for uniform matter supplemented by the Shen EOS for non-uniform matter at low densities, we perform general-relativistic spherically symmetric simulations of core-collapse SNe with and without neutrino transfer, starting from a presupernova model of 15 M-circle dot. In the adiabatic simulation without neutrino transfer, the explosion is successful, and the explosion energy with the variational EOS is larger than that with the Shen EOS. In the case of the simulation with neutrino transfer, the shock wave stalls and then the explosion fails, as in other spherically symmetric simulations. The inner core with the variational EOS is more compact than that with the Shen EOS, due to the relative softness of the variational EOS. This implies that the variational EOS is more advantageous for SN explosions than the Shen EOS.

    DOI

    Scopus

    11
    Citation
    (Scopus)
  • Nuclear Equation of State for Core-Collapse Supernovae with Realistic Nuclear Forces

    H. Togashi, Y. Takehara, S. Yamamuro, K. Nakazato, H. Suzuki, K. Sumiyoshi, M. Takano

    POS(NIC XIII)     169 - 169  2014  [Refereed]

  • Equation of state for nuclear matter in core-collapse supernovae by the variational method

    H. Togashi, Y. Takehara, S. Yamamuro, K. Makazato, H. Suzuki, K. Sumiyoshi, M. Takano

    3RD INTERNATIONAL WORKSHOP ON STATE OF THE ART IN NUCLEAR CLUSTER PHYSICS   569   012058  2014  [Refereed]

     View Summary

    We construct a new nuclear equation of state (EOS) for core-collapse supernova (SN) simulations using the variational many-body theory. For uniform nuclear matter, the EOS is constructed with the cluster variational method starting from the realistic nuclear Hamiltonian composed of the Argonne v18 two-body potential and the Urbana IX three-body potential. The masses and radii of neutron stars calculated with the obtained EOS at zero temperature are consistent with recent observational data. For non-uniform nuclear matter, we construct the EOS in the Thomas-Fermi approximation. In this approximation, we assume a functional form of the density distributions of protons, neutrons, and alpha-particles, and minimize the free energy density in a Wigner-Seitz cell with respect to the parameters included in the assumed density distribution functions. The phase diagram of hot nuclear matter at a typical temperature is reasonable as compared with that of the Shen EOS.

    DOI

    Scopus

  • Shell effects in hot nuclei and their influence on nuclear composition in supernova matter

    Suguru Nishimura, Masatoshi Takano

    ORIGIN OF MATTER AND EVOLUTION OF GALAXIES 2013   1594   239 - 244  2014  [Refereed]

     View Summary

    We calculate nuclear composition in supernova (SN) matter explicitly taking into account the temperature dependence of nuclear shell effects. The abundance of nuclei in SN matter is important in the dynamics of core-collapse supernovae and, in recently constructed equations of state (EOS) for SN matter, the composition of nuclei are calculated assuming nuclear statistical equilibrium wherein the nuclear internal free energies govern the composition. However, in these EOS, thermal effects on the shell energy are not explicitly taken into account. To address this shortfall, we calculate herein the shell energies of hot nuclei and examine their influence on the composition of SN matter. Following a simplified macroscopic-microscopic approach, we first calculate single-particle (SP) energies by using a spherical Woods-Saxon potential. Then we extract shell energies at finite temperatures using Strutinsky method with the Fermi distribution as the average occupation probability of the SP levels. The results show that at relatively low temperatures, shell effects are still important and magic nuclei are abundant. However, at temperatures above approximately 2 MeV, shell effects are almost negligible, and the mass fractions with shell energies including the thermal effect are close to those obtained from a simple liquid drop model at finite temperatures.

    DOI

    Scopus

    5
    Citation
    (Scopus)
  • Explicit Energy Functional for Infinite Nuclear Matter with the Tensor Force

    M. Takano, K. Kato, M. Yamada

    17TH INTERNATIONAL CONFERENCE ON RECENT PROGRESS IN MANY-BODY THEORIES (MBT17)   529   012025  2014  [Refereed]

     View Summary

    We have applied the variational method using explicit energy functionals (EEFs) to energy calculations of infinite nuclear matter. In EEFs, the energy per nucleon is explicitly expressed with spin-isospin-dependent two-body distribution functions, which are regarded as variational functions, and fully minimized energies are conveniently calculated with the EEF. A remarkable feature of this approach is that EEFs guarantee non-negativeness of structure functions. In this study, we extend the EEF variational method so as to consider stateindependent three-body forces for neutron matter at finite temperatures following the procedure proposed by Schmidt and Pandharipande. For neutron matter, the free energies obtained with the Argonne v4' two-body potential and the repulsive part of the Urbana IX (UIX) threebody potential are quite reasonable. Furthermore, we improve the EEF of nuclear matter using the two-body central and tensor forces by considering the main three-body cluster terms and guaranteeing non-negativeness of tensor structure functions. In addition, healing distances are introduced for two-body distribution functions so that Mayer's condition is satisfied. The obtained energies per neutron of neutron matter with the Argonne v6' two-body potential and the repulsive part of the UIX potential are in good agreement with those obtained by auxiliary field diffusion Monte Carlo calculations.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Nuclear equation of state with the variational method and its application to supernova simulations

    H. Togashi, M. Takano, K. Sumiyoshi, K. Nakazato

    Int. J. Mod. Phys. Conf. Series   29   1460221-1 - 1460221-9  2014  [Refereed]

     View Summary

    We report on an equation of state (EOS) of hot asymmetric nuclear matter constructed using the variational method and its application to hydrodynamic simulations of core-collapse supernovae. This nuclear EOS is based on the AV18 two-body potential and UIX three-body potential, and the energy per nucleon at zero temperature is constructed with the cluster variational method. At finite temperatures, the free energies per nucleon are calculated with an extension of the variational method devised by Schmidt and Pandharipande. This EOS is in good agreement with that by the Fermi hypernetted chain variational calculations at zero and finite temperatures, and the structure of neutron stars calculated with this EOS is consistent with recent observational data. Using this nuclear EOS, we perform a spherically symmetric general-relativistic adiabatic simulation of the SN explosion. The explosion energy calculated with our EOS in the present simulation is larger than that obtained with the Shen EOS, implying that the variational EOS is softer than the Shen EOS.

    DOI

  • New Nuclear Equation of State for Core-Collapse Supernovae with the Variational Method

    H. Togashi, S. Yamamuro, K. Nakazato, M. Takano, H. Suzuki, K. Sumiyoshi

    INPC 2013 - INTERNATIONAL NUCLEAR PHYSICS CONFERENCE, VOL. 2   66   07026  2014  [Refereed]

     View Summary

    We report the current status of our project to construct a new nuclear equation of state (EOS) with the variational method for core-collapse supernova (SN) simulations. Starting from the realistic nuclear Hamiltonian, the EOS for uniform nuclear matter is constructed with the cluster variational method: For non-uniform nuclear matter, the EOS is calculated with the Thomas-Fermi method. The obtained thermodynamic quantities of uniform matter are in good agreement with those with more sophisticated Fermi Hypernetted Chain variational calculations, and phase diagrams constructed so far are close to those of the Shen-EOS. The structure of neutron stars calculated with this EOS at zero temperature is consistent with recent observational data, and the maximum mass of the neutron star is slightly larger than that with the Shen-EOS. Using the present EOS of uniform nuclear matter, we also perform the 1D simulation of the core-collapse supernovae by a simplified prescription of adiabatic hydrodynamics. The stellar core with the present EOS is more compact than that with the Shen-EOS, and correspondingly, the explosion energy in this simulation with the present EOS is larger than that with the Shen-EOS.

    DOI

    Scopus

  • Variational study for the equation of state of asymmetric nuclear matter at finite temperatures

    H. Togashi, M. Takano

    NUCLEAR PHYSICS A   902   53 - 73  2013.03  [Refereed]

     View Summary

    An equation of state (EOS) for uniform asymmetric nuclear matter (ANM) is constructed at zero and finite temperatures by the variational method starting from the nuclear Hamiltonian that is composed of the Argonne v18 and Urbana IX potentials. At zero temperature, the two-body energy is calculated with the Jastrow wave function in the two-body cluster approximation which is supplemented by Mayer's condition and the healing-distance condition so as to reproduce the result by Akmal, Pandharipande and Ravenhall. The energy caused by the three-body force is treated somewhat phenomenologically so that the total energy reproduces the empirical saturation conditions. The masses and radii of neutron stars obtained with the EOS are consistent with recent observational data. At finite temperatures, thermodynamic quantities such as free energy, internal energy, entropy, pressure and chemical potentials are calculated with an extension of the method by Schmidt and Pandharipande. The validity of the frozen-correlation approximation employed in this work is confirmed as compared with the result of the fully minimized calculation. The quadratic proton-fraction-dependence of the energy of ANM is confirmed at zero temperature, whereas the free energy of ANM deviates from the quadratic proton-fraction-dependence markedly at finite temperatures. The obtained EOS of ANM will be an important ingredient of a new nuclear EOS for supernova numerical simulations. (C) 2013 Elsevier B.V. All rights reserved.

    DOI

    Scopus

    46
    Citation
    (Scopus)
  • Cluster Variational Method for Nuclear Matter with the Three-Body Force

    M. Takano, H. Togashi, S. Yamamuro, K. Nakazato, H. Suzuki

    ORIGIN OF MATTER AND EVOLUTION OF GALAXIES 2011   1484   378 - 380  2012  [Refereed]

     View Summary

    We report the current status of our project to construct a new nuclear equation of state (EOS), which may be used for supernova numerical simulations, based on the cluster variational method starting from the realistic nuclear Hamiltonian. We also take into account a higher-order correction to the energy of the nuclear three-body force (TBF). The nuclear EOSs with and without the higher-order TBF correction at zero temperature are very close to each other, when parameters are readjusted so as to reproduce the empirical saturation data.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • Variational Method for Nuclear Matter with an Explicit Energy Functional

    M. Takano, T. Togashi, S. Yamamuro, K. Nakazato, H. Suzuki

    Proceedings of Science (NIC XII)     236  2012  [Refereed]

  • エネルギー汎関数を用いた変分法による核物質状態方程式の研究(バリオン物質と中性子星,研究会報告)

    鷹野 正利, 田中 利典, 山田 勝美

    素粒子論研究   119 ( 2 ) B62 - B64  2011.08

     View Summary

    エネルギー汎関数を用いた変分法により、一様核物質の一核子当たりのエネルギーを求める研究の現状を報告する。本変分法では一核子当たりのエネルギーを2体分布関数の汎関数として陽に表すことにより、十分に最小化されたエネルギーを得る。現状で特に2体核力の非中心力成分を考慮すると、本変分法で計算されたエネルギーが低くなる傾向があるため、拡張したMayer条件を考慮するなど、本変分法の改良を進めている。

    DOI CiNii

  • The Equation of State of Asymmetric Nuclear Matter at Zero and Finite Temperatures with the Variational Method

    H. Togashi, H. Kanzawa, M. Takano

    Proceedings of Science (NIC XI)     179  2011  [Refereed]

    DOI

  • Variational Calculation for the Equation of State of Hot Asymmetric Nuclear Matter

    Togashi, Hajime, Kanzawa, Hiroaki, Takano, Masatoshi

    10TH INTERNATIONAL SYMPOSIUM ON ORIGIN OF MATTER AND EVOLUTION OF GALAXIES   1269   403 - +  2010  [Refereed]

     View Summary

    We calculate the equation of state (EOS) of asymmetric nuclear matter at finite temperatures with the cluster variational method based on the realistic nuclear Hamiltonian composed of the AV18 and UIX nuclear potentials. The free energy is calculated with an extension of the variational method proposed by Schmidt and Pandharipande. The obtained thermodynamic quantities such as entropy, internal energy, pressure and chemical potential derived from the free energy are reasonable. It is also found that the present variational calculation is self-consistent. These thermodynamic quantities are essential ingredients in our project for constructing a new nuclear EOS applicable to supernova simulations.

    DOI

    Scopus

  • Variational Approach to Nuclear Matter

    Takano, Masatoshi, Togashi, Hajime, Kanzawa, Hiroaki

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT   ( 186 ) 63 - 68  2010  [Refereed]

     View Summary

    We calculated the energies of asymmetric nuclear matter at zero and finite temperatures with the cluster variational method. At zero temperature, the expectation value of the two-body Hamiltonian composed of the kinetic energies and the AV18 two-body forces is calculated with the Jastrow wave function in the two-body cluster approximation. The obtained two-body energy is in good agreement with the result with the Fermi Hypernetted Chain (FHNC) calculation by Akmal et al. The energy caused by the UIX three-body forces is treated somewhat phenomenologically so that the total energy reproduces the empirical saturation point. Furthermore, the parameters included in the three-body energy are readjusted so that the Thomas-Fermi (TF) calculations with use of the obtained energy of nuclear matter reproduce the gross feature of the experimental data on atomic nuclei. The nuclear species in the neutron star crust obtained by the TF calculation are reasonable. The free energies of asymmetric nuclear matter at finite temperatures are calculated with an extension of the method proposed by Schmidt and Pandharipande. The obtained free energies are in good agreement with those with the FHNC method, and it is also found that the present variational method is self-consistent. It is remarkable that the symmetry free energy is not proportional to (1 - 2x)(2), where x is the proton fraction. With use of the obtained thermodynamic quantities, we are constructing a new nuclear equation of state for supernova simulations.

  • Nonuniform Matter in Neutron Star Crusts Studied by the Variational Method with Thomas-Fermi Calculations

    Hiroaki Kanzawa, Masatoshi Takano, Kazuhiro Oyamatsu, Kohsuke Sumiyoshi

    PROGRESS OF THEORETICAL PHYSICS   122 ( 3 ) 673 - 691  2009.09  [Refereed]

     View Summary

    The equation of state (EOS) for neutron star (NS) crusts is studied in the Thomas-Fermi (TF) approximation using the EOS for uniform nuclear matter obtained by, the variational method with the realistic nuclear Hamiltonian. The parameters associated with the nuclear three-body force, which are introduced to describe the saturation properties, are finely adjusted so that the TF calculations for isolated atomic nuclei reproduce the experimental data on masses and charge distributions satisfactorily. The resulting root-mean-square deviation of the masses from the experimental data for mass-measured nuclei is about 3 MeV. With the use of the nuclear EOS thus obtained, the nuclear species in the NS crust at zero temperature are determined. The predicted proton numbers of the nuclei in the NS crust are close to the gross behavior of the results obtained by Negele and Vautherin, while they are larger than those for the EOS obtained by Shen et al. owing to the difference in the symmetry energy. The density profile of NS is calculated with the constructed EOS.

  • VARIATIONAL CALCULATION FOR THE NUCLEAR EQUATION OF STATE TOWARD SUPERNOVA EXPLOSIONS

    Masatoshi Takano, Hiroaki Kanzawa, Kazuhiro Oyamatsu, Kohsuke Sumiyoshi

    MODERN PHYSICS LETTERS A   23 ( 27-30 ) 2455 - 2458  2008.09  [Refereed]

     View Summary

    The equation of state (EOS) is calculated for uniform nuclear matter at zero and finite temperatures with the variational method. Making use of uncertainty of the three-body nuclear force, adjustable parameters in the nuclear EOS are tuned so that the Thomas-Fermi calculations for beta-stable nuclei with the EOS reproduce the empirical data. The calculated nuclear properties imply that larger symmetry energy of the EOS is preferable to reproduce the empirical beta-stability line. The expectation value of the nuclear Hamiltonian caused by the 2 pi-exchange three-body nuclear force is uncertain and related to the symmetry energy.

  • APPROXIMATE ENERGY EXPRESSION FOR NUCLEAR MATTER WITH NECESSARY CONDITIONS ON TENSOR STRUCTURE FUNCTIONS

    Kazunori Tanaka, Masatoshi Takano

    MODERN PHYSICS LETTERS A   23 ( 27-30 ) 2593 - 2596  2008.09  [Refereed]

     View Summary

    The approximate energy expression for neutron matter is refined with respect to the tensor forces. The refined energy expression includes the main part of the three-body-cluster kinetic-energy terms caused by tensor correlations appropriately. Furthermore, the new energy expression guarantees necessary conditions on tensor structure functions. Significant improvement is seen in the numerical results of the variational calculation with the refined energy expression for neutron matter.

  • Variational calculation of the equation of state of nuclear matter

    M. Takano, H. kanzawa, K. Sumiyoshi, K. Oyamatsu

    Series on Advances in Quantum Many-Body Theory   11   181 - 184  2008

  • Refinement of the variational method with approximate energy expressions by taking into account 4-body cluster terms

    K. Tanaka, M. Takano

    Series on Advances in Quantum Many-Body Theory   11   185 - 189  2008

  • Variational calculations for the nuclear equation of state toward supernova simulations

    H. Kanzawa, K. Oyamatsu, K. Sumiyoshi, M. Takano

    ORIGIN OF MATTER AND EVOLUTION OF GALAXIES   1016   261 - +  2008  [Refereed]

     View Summary

    We construct an equation of state (EOS) for uniform nuclear matter at zero and finite temperatures with the variational method starting from the realistic nuclear Hamiltonian composed of the AV18 two-body potential and the UIX three-body interaction. Using the obtained EOS, we perform the Thomas-Fermi calculation of atomic nuclei, and tune adjustable parameters in the EOS for uniform matter to reproduce empirical data of beta-stable nuclei, toward a nuclear EOS table for supernova simulations.

  • Approximate energy expression for nuclear matter with tensor structure functions

    Kazunori Tanaka, Masatoshi Takano

    ORIGIN OF MATTER AND EVOLUTION OF GALAXIES   1016   293 - 298  2008  [Refereed]

     View Summary

    We refine the approximate energy expression for neutron matter by taking into account three-body cluster terms with tensor correlations. The energy expression is an explicit functional of two-body distribution functions and used conveniently in the variational method. The energy expression proposed previously does not include kinetic energy terms caused by noncentral correlations sufficiently, and the obtained energy is too low. In this study, we refine the energy expression by introducing the main part of the missing three-body cluster terms that are related to the tensor correlations. The refined energy expression automatically guarantees necessary conditions on tensor structure functions. The obtained energy per neutron with the v6'potential is considerably higher than that of the old energy expression.

  • Nuclear Many-Body Approach for Supernova EOS: Thomas-Fermi Calculations of Non-Uniform Nuclear Matter

    H. Kanzawa, K. Oyamatsu, K. Sumiyoshi, M. Takano

    Proceedings of Science (NIC X)     108  2008  [Refereed]

  • Variational Calculations of Nuclear Matter with Approximate Energy Expression

    K. Tanaka, M. Takano

    Proceedings of Science (NIC X)     193  2008  [Refereed]

  • Variational Calclation for the Equation of State of Nuclear Matter toward Supernova Simulations

    H. Kanzawa, K. Oyamatsu, K. Sumiyoshi, M. Takano

    Physics of Self-Organization Systems     199 - 208  2008  [Refereed]

  • Variational calculation for the equation of state of nuclear matter at finite temperatures

    H. Kanzawa, K. Oyamatsu, K. Sumiyoshi, M. Takano

    NUCLEAR PHYSICS A   791 ( 1-2 ) 232 - 250  2007.07  [Refereed]

     View Summary

    An equation of state (EOS) for uniform nuclear matter is constructed at zero and finite temperatures with the variational method starting from the realistic nuclear Hamiltonian composed of the Argonne V18 and UIX potentials. The energy is evaluated in the two-body cluster approximation with the three-body-force contribution treated phenomenologically so as to reproduce the empirical saturation conditions. The obtained energies for symmetric nuclear matter and neutron matter at zero temperature are in fair agreement with those by Akmal, Pandharipande and Ravenhall, and the maximum mass of the neutron star is 2.2M(circle dot). At finite temperatures, a variational method by Schmidt and Pandharipande is employed to evaluate the free energy, which is used to derive various thermodynamic quantities of nuclear matter necessary for supernova simulations. The result of this variational method at finite temperatures is found to be self-consistent. (c) 2007 Elsevier B.V. All rights reserved.

    DOI

    Scopus

    44
    Citation
    (Scopus)
  • Equation of state of nuclear matter and the nuclear three-body force

    H. Kanzawa, K. Oyamatsu, K. Sumiyoshi, M. Takano

    NEW FACET OF THREE NUCLEON FORCE - 50 YEARS OF FUJITA MIYAZAWA THREE NUCLEON FORCE (FM 50)   1011   287 - +  2007  [Refereed]

     View Summary

    An equation of state (EOS) for uniform nuclear matter is constructed at zero and finite temperatures with the variational method starting from a realistic nuclear Hamiltonian composed of the AV18 two-body potential and the UIX three-nucleon interaction (TNI). The two-body energy is calculated with a Jastrow wave function, and the TNI energy with the Fermi-gas wave function. In this calculation, the Fujita-Miyazawa (FM) 2 pi-exchange term of the TNI energy is positive for symmetric nuclear matter. By taking into account the correlation between nucleons perturbatively, the expectation value of the FM term is modified to be negative in the low density region.

  • High performance solid-state track detector for the observation of trans-ion isotopes in galactic cosmic rays

    Satoshi Kodaira, Tadayoshi Doke, Makoto Hareyama, Nobuyuki Hasebe, Takashi Miyachi, Mitsuhiro Miyajima, Osamu Okudaira, Kunitomo Sakurai, Masatoshi Takano, Shoji Torii, Naoyuki Yamashita, Nakahiro Yasuda, Hiroko Tawara, Shogo Nakamura, Koichi Ogura, Hiros

    Proceedings of 20th European Cosmic Ray Symosium    2006.09

  • The high precision observation of ultra heavy cosmic ray nuclei

    Nobuyuki Hasebe, Tadayoshi Doke, Makoto Hareyama, Satoshi Kodaira, Takashi Miyachi, Mitsuhiro Miyajima, Osamu Okudaira, Kunitomo Sakurai, Masatoshi Takano, Shoji Torii, Naoyuki Yamashita, Nakahiro Yasuda, Shogo Nakamura, Hiroko Tawara, Koichi Ogura, Hiros

    Proceedings of 20th European Cosmic Ray Symposium    2006.09

  • Variational study of asymmetric nuclear matter and a new term in the mass formula

    Masatoshi Takano, Masami Yamada

    PROGRESS OF THEORETICAL PHYSICS   116 ( 3 ) 545 - 571  2006.09  [Refereed]

     View Summary

    Asymmetric nuclear matter at zero temperature is studied using a variational method which is an extension of the methods used by the present authors previously for simpler systems. An approximate expression for the energy per nucleon in asymmetric nuclear matter is derived through a combination of two procedures, one used for symmetric nuclear matter and the other for spin-polarized liquid He-3 with spin polarization replaced by isospin polarization. The approximate expression for the energy is obtained as a functional of various spin-isospin-dependent radial distribution functions, tenser distribution functions, and spin-orbit distribution functions. The Euler-Lagrange equations are derived to minimize this approximate expression for the energy; they consist of 16 coupled integro differential equations for various distribution functions. These equations were solved numerically for several values of the nucleon number density rho and for many degrees of asymmetry zeta[zeta = (rho(n) - rho(p)/rho, where rho(n)(rho(p)) is the neutron (proton) number density]. Unexpectedly, we find that the energies at a fixed density cannot be represented by a power series in zeta(2). A new energy term, epsilon(1)(zeta(2) + zeta 0(2))(1/2) where zeta(0) is a small number and epsilon(1) is a positive coefficient, is proposed. It is shown that if the power series is supplemented with this new term, it reproduces the energies obtained by variational calculations very accurately. This new term is studied in relation to cluster formation in nuclear matter, and some mention is made of a possible similar term in the mass formula for finite nuclei.

  • The origin of helium-3 isotope enhancement in the magnetosphere observed by TSUBASA satellite

    Hareyama M, Fujii M, Hasebe N, Kajiwara N, Kodaira S, Sakurai K, Takano M, Goka T, Koshiishi H, Matsumoto H

    Astroparticle, Particle and Space Physics, Detectors and Medical Physics Applications - Proceedings of the 9th Conference     940 - 944  2006  [Refereed]

  • 宇宙線超重核観測計画

    長谷部信行, 道家忠義, 晴山慎, 櫻井邦朋, 小平聡, 鷹野正利, 鳥居祥二, 宮地孝, 宮島光弘, 奥平修, 山下直之, 安田仲宏, 俵裕子, 中村正吾, 小倉紘一, 渋谷寛

    Space Radiation   5   3 - 37  2006

  • 変分法による一様核物質の状態方程式の研究

    鷹野正利

    素粒子論研究   111 ( 4 ) D20  2005.07

  • Phase transitions in nucleonic matter and neutron-star cooling

    VA Khodel, JW Clark, M Takano, MV Zverev

    PHYSICAL REVIEW LETTERS   93 ( 15 ) 151101  2004.10  [Refereed]

     View Summary

    A new scenario for neutron-star cooling is suggested by the correspondence between pion condensation, induced by critical spin-isospin fluctuations, and the metal-insulator phase transition in a 2D electron gas. Above the threshold density for pion condensation, the neutron single-particle spectrum acquires an insulating gap that quenches neutron contributions to neutrino production. In the liquid phase just below the transition, the fluctuations play dual roles by (i) creating a multisheeted neutron Fermi surface that extends to low momenta and activates the normally forbidden direct Urca cooling mechanism, and (ii) amplifying the nodeless P-wave neutron superfluid gap while suppressing S-wave pairing. Lighter stars without a pion-condensed core undergo slow cooling, whereas enhanced cooling occurs in heavier stars via direct Urca emission from a thin shell of the interior.

    DOI

    Scopus

    36
    Citation
    (Scopus)
  • Variational calculations for the equation of state of asymmetric nuclear matter

    M Takano

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT   156 ( 156 ) 141 - 142  2004  [Refereed]

     View Summary

    Two variational methods are used to calculate energies per nucleon of asymmetric nuclear matter. One is the explicit energy functional method, in which approximate energy expressions are proposed as explicit functionals of the variational functions. The other is the two-body, cluster variational method. The numerical results show that, in both cases, the saturation densities decrease markedly as the proton fraction decreases.

  • Approximate energy expression for spin-polarized Fermi liquids

    M Takano, T Endo, R Kimura, M Yamada

    PROGRESS OF THEORETICAL PHYSICS   109 ( 2 ) 213 - 232  2003.02  [Refereed]

     View Summary

    An approximate energy expression is proposed for arbitrarily spin-polarized Fermi liquids with central two-body forces. It is explicitly expressed as a functional of spin-dependent radial distribution functions and can be used conveniently in the variational method. It includes the potential energies completely and the kinetic energies up to main parts of the three-body cluster terms. This approximation is similar to that used previously for spin-unpolarized and fully polarized matter. A notable feature of this expression is that it guarantees the necessary conditions on arbitrarily spin-polarized structure functions automatically. The Euler-Lagrange equations are derived from this energy expression and are numerically solved for arbitrarily spin-polarized liquid 3 He. The results for liquid He-3 with the HFDHE2 potential are consistent with the nearly ferromagnetic property.

  • Variational method for infinite nuclear matter with the Paris potential

    M Takano

    PROGRESS OF THEORETICAL PHYSICS   104 ( 1 ) 185 - 202  2000.07  [Refereed]

     View Summary

    The energy per nucleon for infinite nuclear matter with the parametrized Paris potential is calculated using the variational method recently proposed by Takano and Yamada. Approximate energy expressions playing an important role in this variational method are refined for the Paris potential, and in particular for the quadratic momentum parts in it. Since this variational method without any constraints gives extreme overbinding, an effective theory also proposed in conjunction with the above-mentioned variational method is applied, in a modified manner, to the calculations for symmetric nuclear matter and neutron matter with the Paris potential, as well as the Hamada-Johnston and AV14 potentials. The obtained equation of state (EOS) for the Paris potential is, unlike the unrealistically soft EOS for the AV14 potential, capable of describing neutron stars with a reasonable maximum mass of 1.65 M-..

  • 変分法による一様核物質の状態方程式

    東京大学理学部初期宇宙研究センター研究会「中性子星の誕生と進化: 観測と理論の新展開」    1998.12

  • Variational method for infinite nuclear matter with noncentral forces

    M Takano, M Yamada

    PROGRESS OF THEORETICAL PHYSICS   100 ( 4 ) 745 - 771  1998.10  [Refereed]

     View Summary

    Approximate energy expressions are proposed for infinite zero-temperature neutron matter and symmetric nuclear matter by taking into account noncentral forces. They are explicitly expressed as functionals of spin-isospin-dependent radial distribution functions, tensor distribution functions and spin-orbit distribution functions: and can be used conveniently in the variational method. The two-body noncentral cluster terms are fully included in these expressions, while the degree of inclusion of the three-body cluster terms related to noncentral forces is less than that of the purely central three-body terms. The Euler-Lagrange equations are derived from these energy expressions and numerically solved for neutron matter and symmetric nuclear matter. The Hamada-Johnston and AV14 potentials are used as the two-body nuclear force. The results show that the noncentral forces cause the total energy of symmetric nuclear matter to be decreased too much with a saturation density which is too high. Discussion is given as to the reason for this disagreement with experiment, and the long tails of the noncentral distribution functions obtained in the numerical calculations are suspected to be the main reason. Then, an effective theory is proposed by introducing a density-dependent modification of the noncentral part of the energy expression to suppress the long tails of the noncentral distribution functions. With a suitable choice of the value of a parameter included in the modification, the saturation point (both the energy and the density) of symmetric nuclear matter can be reproduced with the Hamada-Johnston potential. Neutron stars are studied by use of this effective theory, and reasonable results are obtained.

  • Variational method for infinite nuclear matter with noncentral forces

    M. Takano, M. Yamada

    The Proceedings of the 9th International Conference on Recent Progress in Many-Body Theories   Series on Advances in Quantum Many-Body Theory - Vol. 1   238 - 242  1998.01

  • A variational method for infinite nuclear matter with approximate energy expressions

    M. Takano, M. Yamada

    Pulsars and Neutron Stars: Thirty years after the discovery     165 - 168  1998.01

  • Refinement of the energy expression for infinite fermion systems with central forces

    M Takano, T Kaneko, M Yamada

    PROGRESS OF THEORETICAL PHYSICS   97 ( 4 ) 569 - 577  1997.04  [Refereed]

     View Summary

    A refinement is made on the approximate energy expression proposed previously by Takano and Yamada for infinite zero-temperature systems of spin-1/2 fermions interacting through two-body central forces which may depend on the two-body spin states. This refinement is accomplished through incorporation of a certain part of the three-body-cluster exchange terms into the energy expression. The Euler-Lagrange equation is derived from the refined energy expression and solved numerically for liquid He-3 and for neutron matter. The energy per particle for liquid He-3 is in better agreement with experimental data, while the effect of this refinement is relatively small for neutron matter. The three-body cluster terms not included in the refined energy expression are evaluated perturbatively and shows to be negligibly small for liquid He-3 as well as for neutron matter with central forces.

  • APPROXIMATE ENERGY EXPRESSION FOR SYMMETRICAL NUCLEAR-MATTER WITH CENTRAL FORCES

    M TAKANO

    PROGRESS OF THEORETICAL PHYSICS   93 ( 4 ) 745 - 756  1995.04  [Refereed]

     View Summary

    An approximate energy expression is proposed for infinite zero-temperature symmetric nuclear matter in which nucleons interact through two-body central forces depending on the two-body spin-isospin states. It is a functional of spin-isospin-dependent radial distribution functions, and includes the potential energies completely and the kinetic energies up to the main part of the three-body cluster terms. A notable feature of this expression is that it automatically guarantees the necessary conditions on the spin-isospin-dependent structure functions. This expression is conveniently used in the variational method; the Euler-Lagrange equations are derived and numerically solved for four typical potentials. The obtained energies per nucleon are shown together with the spin-isospin-dependent radial distribution functions and structure functions.

  • A VARIATIONAL METHOD FOR INFINITE FERMION SYSTEMS WITH CENTRAL FORCES

    M TAKANO, M YAMADA

    PROGRESS OF THEORETICAL PHYSICS   91 ( 6 ) 1149 - 1172  1994.06  [Refereed]

     View Summary

    Approximate energy expressions are proposed for infinite zero-temperature systems of spin-1/2 fermions interacting through two-body central forces which may depend on the two-body spin states. They are explicitly expressed as functionals of spin-dependent radial distribution functions, and can be used conveniently in the variational method. They include the potential energies completely and the kinetic energies up to main parts of the three-body cluster terms. A notable feature of these expressions is that they guarantee the necessary conditions on the spin-dependent structure functions automatically. The Euler-Lagrange equations are derived from these energy expressions and numerically solved for liquid He-3 and hypothetical neutron matter interacting only through central forces. The parts of the three-body cluster terms which are not included in the above expressions are treated perturbatively. The results for liquid He-3 are in fair agreement with experiment. The obtained spin-dependent radial distribution functions and structure functions are discussed in relation with pairing and cluster formation.

  • NECESSARY CONDITIONS ON SPIN-ISOSPIN-DEPENDENT LIQUID STRUCTURE FUNCTIONS OF FERMION SYSTEMS

    M TAKANO, M YAMADA

    PROGRESS OF THEORETICAL PHYSICS   88 ( 6 ) 1131 - 1145  1992.12  [Refereed]

     View Summary

    Spin-isospin-dependent liquid structure functions are defined in terms of the projection operators onto particular spin-isospin pair states. Then, necessary conditions on these structure functions are derived in the form of inequalities. The systems studied are liquid He-3, neutron matter, symmetric nuclear matter, asymmetric nuclear matter, and partially spin-polarized asymmetric nuclear matter. More than one inequalities is obtained for each of these systems, and the number of the inequalities increases with increase of the spin-isospin degree of freedom. It is argued that these conditions can be used to find approximate kinetic-energy expressions of fermion systems.

▼display all

Presentations

  • 核子間相関を考慮した核子制動放射による超新星物質からのニュートリノ放出率

    鷹野正利, 富樫甫, 住吉光介

    日本物理学会2024春 

    Presentation date: 2024.03

    Event date:
    2024.03
     
     
  • クラスター変分法を用いた有限温度核物質からの核子制動放射によるニュートリノ放出率

    鷹野正利, 富樫甫, 住吉光介

    第10回超新星ニュートリノ研究会 

    Presentation date: 2024.03

    Event date:
    2024.02
    -
    2024.03
  • 核子間相関を考慮した核物質からのニュートリノ放出率

    鷹野正利, 富樫甫

    日本物理学会 

    Presentation date: 2023.09

    Event date:
    2023.09
     
     
  • クラスター変分法による核子制動放射過程のニュートリノ放射率II

    鷹野正利, 富樫甫

    日本物理学会 

    Presentation date: 2023.03

    Event date:
    2023.03
     
     
  • クラスター変分法に基づく核子制動放射のニュートリノ放射率の精密化

    鷹野正利

    第9回超新星ニュートリノ研究会 

    Presentation date: 2023.03

    Event date:
    2023.03
     
     
  • クラスター変分法による核子制動放射率の計算

    鷹野正利

    京都ミーティング2022b 

    Presentation date: 2022.12

    Event date:
    2022.12
     
     
  • クラスター変分法による核子制動放射過程のニュートリノ放射率

    鷹野正利, 富樫甫

    日本物理学会 

    Presentation date: 2022.09

    Event date:
    2022.09
     
     
  • スピン・軌道力を考慮した対称核物質に対するエネルギー汎関数を用いた変分法

    不島昇士, 佐藤徹, 鷹野正利

    日本物理学会 

    Presentation date: 2022.03

    Event date:
    2022.03
     
     
  • クラスター変分法による修正ウルカ過程のニュートリノ放射率計算の改良II

    鷹野正利, 富樫甫

    日本物理学会 

    Presentation date: 2022.03

    Event date:
    2022.03
     
     
  • LOCV法を参照した有限温度核物質からの修正ウルカ過程ニュートリノ放射率計算

    鷹野正利

    第8回超新星ニュートリノ研究会 

    Presentation date: 2022.01

    Event date:
    2022.01
     
     
  • クラスター変分法による修正ウルカ過程のニュートリノ放射率計算の改良

    鷹野正利, 富樫甫

    日本物理学会2021年秋季大会 

    Presentation date: 2021.09

    Event date:
    2021.09
     
     
  • 相対論的boost補正の効果を考慮した陽なエネルギー汎関数を用いた変分法による一様核物質の研究

    鷹野正利, 不島昇士, 佐藤徹

    日本物理学会第76回年次大会 

    Presentation date: 2021.03

    Event date:
    2021.03
     
     
  • 修正ウルカ過程のニュートリノ放出率計算のための核物質中の核子間相関の精密化

    鷹野正利, 阿部雄太, 富樫甫

    第7回超新星ニュートリノ研究会 

    Presentation date: 2021.01

    Event date:
    2021.01
     
     
  • クラスター変分法による修正ウルカ過程のニュートリノ放射率II

    鷹野正利, 阿部雄太, 富樫甫

    日本物理学会2020年秋の分科会  (筑波大学(オンライン開催)) 

    Presentation date: 2020.09

  • クラスター変分法による修正ウルカ過程のニュートリノ放射率

    鷹野正利, 阿部雄太, 富樫甫

    日本物理学会 

    Presentation date: 2020.03

  • Variational Methos for nuclear matter and their applications to neutron stars

    Masatoshi Takano  [Invited]

    The Evolution of Massive Stars and Formation of Compact Stars: from the Cradle to the Grave  (Waseda Univ.) 

    Presentation date: 2020.02

  • 核物質状態方程式に対する変分法を用いた修正ウルカ過程のニュートリノ放射率

    鷹野正利

    第6回超新星ニュートリノ研究会  (東京大学宇宙線研究所) 

    Presentation date: 2020.01

  • スピン・軌道力を考慮した一様核物質に対するエネルギー汎関数を用いた変分法の改良

    鷹野正利, 堀川峻洋

    日本物理学会  (大阪) 

    Presentation date: 2017.03

  • Variational method with explicit energy functional for nuclear matter

    Masatoshi Takano  [Invited]

    Nuclear Physics, Compact Stars, and Compact Star Mergers 2016  (YITP, Kyoto, Japan) 

    Presentation date: 2016.10

  • スピン・軌道力を考慮した中性子物質に対するエネルギー汎関数を用いた変分法II

    鷹野正利

    日本物理学会 

    Presentation date: 2015.09

  • Variational calculations with explicit energy functional for fermion systems at zero temperature

    M. Takano, T. Suzuki, N. Sakumichi

    Recent Progress in Many-Body Theories 18 

    Presentation date: 2015.08

  • エネルギー汎関数を用いた変分法による核物質状態方程式の研究

    鷹野正利

    原子核・クォークと中性子星—これまでとこれから− 

    Presentation date: 2015.06

  • An Explicit Energy Functional for Neutron Matter Taking into account the Spin-Orbit Force

    M. Takano, K. Kato

    Fourth Joint Meeting of the Nuclear Physics Divisions of the American Physical Society and The Physical Society of Japan  (Waikoloa Hawaii., USA) 

    Presentation date: 2014.10

  • 一様核物質に対するエネルギー汎関数を用いた変分法の改良III

    鷹野正利, 加藤浩平, 山田勝美

    日本物理学会 

    Presentation date: 2014.03

  • Explicit Energy Functional for Infinite Nuclear Matter with the Tensor Force

    M. Takano, M. Yamada, K. Kato

    Recent Progress on Many-Body Theories 17 

    Presentation date: 2013.09

  • 一様核物質に対するエネルギー汎関数を用いた変分法の改良II

    日本物理学会 

    Presentation date: 2013.03

  • Variational Method with an Explicit Energy Functional for Nuclear Equation of State

    M. Takano

    Quarks to Universe in Computational Science 

    Presentation date: 2012.12

  • 変分法による核物質状態方程式の天体現象への応用

    国立天文台理論天文学研究会2012 

    Presentation date: 2012.11

  • 現実的核力を用いた変分法と核物質状態方程式

    基研研究会「ハドロン物質の諸相と状態方程式—中性子星の観測に照らしてー」 

    Presentation date: 2012.08

  • Variational Method for Nuclear Matter with an Explicit Energy Functional

    M. Takano, K. Tanaka, M. Yamada, S. Yamamuro, H. Suzuki, K. Nakazato, K. Sumiyoshi, H. Matsufuru

    Nuclei in the Cosmos XII 

    Presentation date: 2012.08

  • 一様核物質に対するエネルギ-汎関数を用いた変分法の改良

    日本物理学会(関西学院大学) 

    Presentation date: 2012.03

  • Cluster Variational Method for Nuclear Matter with the Three-Body Force

    M. Takano, H. Togashi, S. Yamamuro, K. Nakazato, H. Suzuki

    The 11th International Symposium on Origin of Matter and Evolution of Galaxies 

    Presentation date: 2011.11

  • Variational calculation for nuclear matter with an explicit energy functional

    M. Takano, K. Tanaka, M. Yamada

    Third International Conference on Nuclear Fragmentation 

    Presentation date: 2011.10

  • エネルギー汎関数を用いた条件つき変分法による核物質の研究III

    日本物理学会(弘前大) 

    Presentation date: 2011.09

  • エネルギー汎関数を用いた条件つき変分法による核物質の研究II

    日本物理学会(新潟大学) 

    Presentation date: 2011.03

  • クラスター変分法による有限温度非対称核物質状態方程式の研究

    超新星からのマルチメッセンジャー:超新星研究会2011 

    Presentation date: 2011.03

  • エネルギー汎関数を用いた変分法による核物質状態方程式の研究

    研究会「バリオン物質と中性子星」 

    Presentation date: 2011.01

  • Variational Calculations for Nuclear Equation of State

    M. Takano

    International Symposium on “From Quarks to Supernovae" 

    Presentation date: 2010.11

  • Variational Approach to Nuclear Matter

    M. Takano  [Invited]

    New Frontiers in QCD 2010 –Exotic Hadron Systems and Dense Matter- 

    Presentation date: 2010.01

  • クラスター変分法と高密度ハドロン物質

    『バリオン間相互作用に基づく核物質の構造』研究会 

    Presentation date: 2009.06

  • 現実的核力に基づく核物質状態方程式計算 ー超新星爆発シミュレーションへの適用を目指してー

    Numazu Workshop 2009クォ-ク力学・原子核構造に基づく爆発的天体現象と元素合成 

    Presentation date: 2009.03

  • クラスター変分法による非対称核物質状態方程式の研究

    日本物理学会 

    Presentation date: 2009.03

  • 変分法による核物質状態方程式の作成と天体物理への応用

    ワークショップ「計算科学による素粒子・原子核・宇宙の融合」 

    Presentation date: 2008.01

  • Variational Calculation for The Nuclear Equation of State Toward Supernova Explosions

    M. Takano, H. kanzawa, K. Oyamatsu, K. Sumiyoshi

    Chiral07, RCNP, Osaka 

    Presentation date: 2007.10

  • Variational Calculation of the Equation of State of Nuclear Matter

    M. Takano, H. Kanzawa, K. Sumiyoshi, K. Oyamatsu

    The 14th International Conference on Recent Progress in Many Body Theories 

    Presentation date: 2007.08

  • Variational Calculation of the Equation of State of Nuclear Matter

    M. Takano, H. Kanzawa, K. Sumiyoshi, K. Oyamatsu

    The 14th International Conference on Recent Progress in Many Body Theories, The Technical University of Cataronia, Barcelona, Spain 

    Presentation date: 2007.07

  • 一様核物質と液体ヘリウム3に対する変分法

    ORIUM COE-Crossroads in Physics(物理学の交差点)シリーズ第一回研究会「宇宙・素粒子・物性物理の境界領域を探る」(名古屋大) 

    Presentation date: 2007.06

  • 超新星爆発計算のための現実的核力に基づく核物質状態方程式の作成

    Numazu Workshop on Supernova EOS 

    Presentation date: 2007.03

  • 宇宙線中の超重核観測計画2−元素合成と宇宙線超重核-

    日本物理学会(首都大) 

    Presentation date: 2007.03

  • Variational calculation for the equation of state of nuclear matter

    M. Takano, H. Kanzawa, K. Oyamatsu, K. Sumiyoshi  [Invited]

    High energy physics on supernova, Tokyo 

    Presentation date: 2007.02

  • 核データに基づく超重元素合成課程の考察

    名古屋大学太陽地球環境研究所研究会、平成18年度太陽圏シンポジウム及びSTE研究集会(名古屋大) 

    Presentation date: 2007.01

  • Equation of state for infinite nuclear matter at finite temperature - a microscopic approach toward supernova simulations-

    M. Takano, H. Kanzawa, K. Oyamatsu, K. Sumiyoshi

    23rd Texas Symposium on Relativistic Astrophysics Texas in Australia 

    Presentation date: 2006.12

  • 変分法による非対称核物質のエネルギーと質量公式への影響

    日本物理学会(奈良女子大学) 

    Presentation date: 2006.09

  • Variational calculation for infinite nuclear matter at finite temperature

    M. Takano, H. Kanzawa, K. Oyamatsu, K. Sumiyoshi

    In heaven and on earth 2006, The nuclear equation of state in astrophysics 

    Presentation date: 2006.07

  • 変分法による一様核物質の状態方程式の研究

    バリオン力とバリオン物質」研究会(盛岡市) 

    Presentation date: 2004.11

  • 非中心力を考慮した非対称核物質に対する近似的エネルギー表式III

    日本物理学会(高知大学) 

    Presentation date: 2004.09

  • An Approximate Energy Expression for Asymmetric Nuclear Matter

    M. Takano

    The 12th International Conference on Recent Progress in Many-Body Theories, Santa Fe, New Mexico, USA 

    Presentation date: 2004.08

  • Variational Calculations for Asymmetric Nuclear Matter

    M. Takano

    International Nuclear Physics Conference 2004, Goeteborg, Sweden 

    Presentation date: 2004.07

  • 非中心力を考慮した非対称核物質に対する近似的エネルギー表式II

    日本物理学会(九州大学箱崎キャンパス) 

    Presentation date: 2004.03

  • Variational calculations for the equation of states of asymmetric nuclear matter

    M. Takano

    workshop on "Nuclear Matter under Extreme Conditions", YITP, Kyoto 

    Presentation date: 2003.12

  • 中性子星物質におけるスピン・アイソスピン揺らぎと直接ウルカ過程

    日本物理学会(宮崎ワールドコンベンションセンターサミット) 

    Presentation date: 2003.09

  • Approximate Energy Expressions for Asymmetric Nuclear Matter

    M. Takano, M. Yamada

    International Nuclear Physics Conference, University of California, Berkeley, California, USA 

    Presentation date: 2001.08

  • Variational method for asymmetric nuclear matter with approximate energy expressions

    M. Takano, M. Yamada

    The 11th International Conference on Recent Progress in Many-Body Theories, UMIST, Manchester, UK 

    Presentation date: 2001.07

  • 非対称核物質に対する近似的エネルギー表式

    日本物理学会(中央大学) 

    Presentation date: 2001.03

  • Variational Method for Infinite Nuclear Matter with Momentum-dependent Nuclear Forces

    M. Takano

    The 10th International Conference on Recent Progress in Many-Body Theories, The University of Washington, Seattle, U. S. A 

    Presentation date: 1999.09

  • 変分法による高密度核物質の状態方程式

    第1回「極限条件におけるハドロン科学」研究会(日本原子力研究所) 

    Presentation date: 1999.03

  • 変分法による一様核物質の状態方程式

    中性子星の誕生と進化:観測と理論の新展開」研究会(東京大学) 

    Presentation date: 1998.12

  • 運動量依存の核力ポテンシャルを用いた変分法

    日本物理学会(秋田大学) 

    Presentation date: 1998.09

  • Equation of state of infinite nuclear matter with a new variational method

    M. Takano, M. Yamada

    International Nuclear Physics Conference, Paris, France 

    Presentation date: 1998.08

  • A variational method for infinite nuclear matter with approximate energy expressions

    M. Takano, M. Yamada

    Pulsars and Neutron Stars: Thirty years after the discovery, Rikkyo Univ. 

    Presentation date: 1997.11

  • 近似的エネルギー表式を用いた一様核物質の状態方程式II

    日本物理学会(都立大) 

    Presentation date: 1997.09

  • 近似的エネルギー表式を用いた一様核物質の状態方程式

    日本物理学会 

    Presentation date: 1997.03

  • Variational Method for Infinite Nuclear Matter with Noncentral Forces

    M. Takano, M. Yamada

    The 9th International Conference on Recent Progress in Many-Body Theories, Sydney, Australia 

    Presentation date: 1997

  • 一様核物質における非中心力相関項の精密化

    日本物理学会 

    Presentation date: 1996.09

  • 核物質中の非中心力相関を含む3体項II

    日本物理学会 

    Presentation date: 1996.03

  • 核物質中の非中心力相関を含む3体項

    日本物理学会 

    Presentation date: 1995.09

  • 非中心力を考慮した核物質の基底状態のエネルギー II

    日本物理学会 

    Presentation date: 1995.03

  • 非中心力を考慮した核物質の基底状態のエネルギー

    日本物理学会 

    Presentation date: 1994.10

  • Energy Expressions of Infinite Fermion Systems for Variational Calculation

    M. Takano, M. Yamada

    The 8th International Conference on Recent Progress in Many-Body Theories, Styria, Austria 

    Presentation date: 1994.08

  • 対称核物質の基底状態に対するエネルギー表式

    日本物理学会 

    Presentation date: 1994.03

  • フェルミ粒子系のエネルギー表式と3体クラスターII

    日本物理学会 

    Presentation date: 1993.10

  • フェルミ粒子系のエネルギー表式と3体クラスター

    日本物理学会 

    Presentation date: 1993.03

  • フェルミ粒子系におけるスピン・アイソスピンに依存した構造関数の条件

    日本物理学会 

    Presentation date: 1992.10

  • 液体3He、中性子物質の絶対零度におけるエネルギーの計算

    日本物理学会 

    Presentation date: 1992.10

  • 半経験的殻項を持つ原子質量公式 II

    日本物理学会 

    Presentation date: 1991.03

  • "Nuclear Mass Formula with a New Type of Shell Terms

    M. Takano, T. Tachibana, M. Uno, M. Yamada

    International Symposium "Structure and Reaction of Unstable Nuclei", Niigata 

    Presentation date: 1991

  • 半経験的殻項を持つ原子質量公式

    日本物理学会 

    Presentation date: 1990.09

▼display all

Research Projects

  • 現実的核力に基づく変分法による核物質状態方程式の作成と原始中性子星への応用

    Project Year :

    2020.04
    -
    2024.03
     

     View Summary

    中性子星内部の高密度核物質では、核子が核力で相互作用しており、中性子星の構造や、重力崩壊型超新星爆発で誕生した原始中性子星の進化は、核物質状態方程式に支配される。本研究では現実的な核力モデルを用いて、新たに開発中の変分法によって核物質状態方程式を計算し、それによって予想される原始中性子星進化の様子を調べる。特に核子の運動量に依存する核力成分を精密に扱うことで、より信頼性の高い核物質状態方程式を求める

  • Theoretical research on supernova neutrinos in connection with nuclear physics and cosmic chemical evolution

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2019.06
    -
    2024.03
     

  • From Quarks to Neutron Stars: Challenges in QCD

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2018.06
    -
    2023.03
     

  • Improvement of the nuclear equation of state for supernova simulations with the variational method starting from realistric nuclear forces

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2013.04
    -
    2018.03
     

    TAKANO Masatoshi, SUMIYOSHI KOHSUKE, SUZUKI HIDEYUKI, YAMADA SHOICHI, NAKAZATO KENICHIRO, TOGASHI HAJIME

     View Summary

    We constructed an equation of state of hot uniform nuclear matter by the cluster variational method starting from realistic nuclear forces, and performed the Thomas-Fermi calculations for non-uniform nuclear matter to obtain a table of the nuclear equation of state applicable to supernova numerical simulations.We also improved the variational method with explicit energy functionals for nuclear matter at zero temperature so as to treat the AV6' (and AV8') two-body potentials and the UIX three-body potential. We further constructed nuclear equations of state at finite temperatures with central forces, and study the impact of the uncertainties in the three-body repulsive force on the structure of proto-neutron stars. Our results are consistent with observational constraints on the neutron star radius obtained from GW170817

  • Construction of the nuclear equation of state with the variational method at finite temperatures and its applications to supernova simulations

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2009.04
    -
    2013.03
     

    TAKANO Masatoshi, OYAMATSU Kazuhiro, SUMIYOSHI Kohsuke, SUZUKI Hideyuki, YAMADA Shoichi

     View Summary

    Starting from the realistic nuclear forces, we constructed the equation of state of uniform nuclear matter that is applicable to core-collapse supernova numerical simulations, using the variational method. With use of the equation of state, we calculated structures of hot proto-neutron stars, and performed supernova simulations. Furthermore, we calculated the equation of state of non-uniform nuclear matter, and then, at typical temperatures, we obtained the phase diagrams of nuclear matter including τ particles, covering a wide range of the density and proton fraction

  • Study of Explosive Astrophysical Phenomena and Nucleosynthesis based on Quark Dynamics and Nuclear Structure

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2008.04
    -
    2013.03
     

    SUZUKI Hideyuki, KAJINO Toshitaka, SUMIYOSHI Kohsuke, UMEDA Hideyuki, SHIBATA Masaru, YAMADA Shoichi, OHNISHI Akira, URYU Kohji, CHIBA Satoshi, IWAMOTO Nobuyuki, YOSHIDA Takashi, OYAMATSU Kazuhiro, TAKANO Masatoshi

     View Summary

    Explosive astrophysical phenomena are studied using numerical simulations based on modern nuclear physics. Dynamics of collapse-driven supernova explosions and of binary neutron star mergers, and emission of neutrinos, gravitational waves, heavy nuclei from them are investigated in detail. Calculation of stellar evolution including progenitors of electron-capture supernovae, development of 3 dimmensional neutrino transfer code, construction of new equation of states for high density matter are also done

  • Nuclear Structure based on Quark Dynamics

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2008.04
    -
    2013.03
     

    HATSUDA Tetsuo, OTSUKA Takaharu, NAKAMURA Atsushi, AOKI Sinya, NAKATSUKASA Takashi, FUJII Shinichiro, HIYAMA Emiko, SHIMIZU Noritaka, SASAKI Shoichi, YABANA Kazuhiro, TAKANO Masatoshi, NEMURA Hidekatsu, SUZUKI Toshio, ISHII Noriyoshi, FUJII Shinichiro

     View Summary

    To derive the nuclear force from first principle lattice quantum chromo dynamics (QCD) simulations, HAL QCD method was developed and established. The equation of state for asymmetric nuclear matter at finite temperature, which is the key input for describing the supernova explosion, was derived on the basis of the cluster variational method. Also, a reduction formula for the Wilson-fermion determinant necessary to study the phase structure of dense QCD was derived. The Gaussian expansion method for quantum few-body calculation was extended to five-body systems with arbitrary two-body interactions. The Monte Carlo shell model, which is powerful method to study the nuclear Hamiltonian with large dimension, was further developed by improving the numerical argorithm and by introducing a new extrapolation method on the basis of the energy variance. A new code of time-dependent density functional theory with particle paring was developed: It lead to a few orders of magnitude numerical speed-up and was applied to study various nuclear collective motions

  • The nuclear equation of state for supernova simulations based on the realistic nuclear forces

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2006
    -
    2008
     

    TAKANO Masatoshi, OYAMATSU Kazuhiro, SUMIYOSHI Kohsuke, YAMADA Shoichi

  • Precise measurement of ultra-heavy nuclei in cosmic rays

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2001
    -
    2004
     

    HASEBE Nobuyuki, MIYCHI Takashi, TAKANO Masatoshi, KOBAYASHI Masanori, SHIBATA Toru

     View Summary

    The trans-iron cosmic rays were observed by balloon experiments using solid-state track detectors and satellite observation of Ariel-6,HEAO-3 and Trek. The measurement accuracies, however, were unsatisfactory because of low charge resolutions of their detectors. Moreover, these are no observations of trans-iron isotope compositions in cosmic rays. The measurement of these compositions gives crucial constrains on a cosmic ray source and a chemical evolution of the galaxy, including their acceleration and propagation processes.
    The basic developments of detectors for trans-iron isotopes and ultra-heavy nuclei up to actinides were performed for future planning of these observations in cosmic rays. Large silicon detectors with high uniformity and the solid-state track detectors such as CR-39 with a high mass resolution of 0.20 amu in rms for iron nuclei were developed in this study. Moreover, in order to establish the analyzing method of cosmic rays, we participated TIGER team of balloon observation. The collision mean-free-paths of Si, Fe and Ni in the atmosphere were obtained with high accuracy with the measurements of energy dependence of those nuclei for total charge-changing cross-sections. Furthermore, the study of high energy phenomena in the solar atmosphere and the interplanetary space is a miniature version occurring in the galaxy and gives an important clue to study dynamical astrophysical processes. In order to understand these phenomena, heavy ions in the radiation belts and from solar particle events were observed using the data from HIT instrument onboard TSUBASA satellite. It is found that the flux ration of helium isotopes, 3He/4He is greatly enhanced in the radiation belt by 3-4 orders of magnitude as compared with the solar abundance ratio. The origin of 3He in radiation belt is still under study.

  • 素粒子・宇宙実験用希ガス液体検出器の開発

    文部科学省 

    Project Year :

    1997
    -
    2001
     

  • 絶対零度核物質状態方程式計算のための変分法の改良

     View Summary

    現実的核力から出発して絶対零度核物質の状態方程式(EOS)を計算するための、エネルギー汎関数を用いた変分法とクラスター変分法の改良を行った。エネルギー汎関数を用いた変分法については、中心力とテンソル力までを考慮したv6'ポテンシャルでの計算法を改良した。前年度に論じたようなMayer条件を考慮する新たな方法として、healing distanceを導入する方法を提案し、またエネルギー汎関数に含まれない3体クラスター補正項の寄与を摂動論的に評価した。それを踏まえ、エネルギー汎関数に取り入れられていないopen-diagramの寄与を取り扱うように理論を拡張したところ、懸案であった対称核物質に対して大幅な改善が見られ、変分法の改良に成功した。さらにKirkwoodの近似に基づく3体力の取り扱い方法を提唱し、中性子物質に対してv6'に加えUIXポテンシャルの斥力部分を考慮した場合について変分計算を行ったところ、Monte Carlo計算結果と良い一致を示した。さらに高密度状態も容易に計算が出来ることを利用して、中性子物質EOSにより中性子星構造を計算したところ、その最大質量は太陽質量の約2.4倍となった。また前年度に引き続きスピン・軌道力を考慮するような理論の拡張も行い、現象論的3体力の寄与を考慮したEOSにおける対称エネルギーの密度依存性を論じた。クラスター変分法については、従来我々が提案してきた方法において3体力の取り扱いの精度を上げるため、UIXポテンシャルの場合に、その3体クラスター項の粒子間相関について最低次の直接項の効果を含むような有効2体力を作成し、それを考慮した核物質EOSを作成した。ここで、核物質飽和点での経験値を再現するようにパラメターを調整した場合、改良したEOSは従来の方法によるEOSと殆ど変わらないことが確認された

▼display all

Misc

  • 16aSG-11 Nuclear Equation of State at Low Densities with the Cluster Variational Method

    Togashi H., Yamamuro S., Kanzawa H., Takano M., Suzuki H.

    Meeting abstracts of the Physical Society of Japan   66 ( 2 ) 35 - 35  2011.08

    CiNii

  • 25aGM-5 Study on the Cluster Variational Method Taking into Account the Nuclear Equation of State at Low Densities

    Togashi H., Kanzawa H., Takano M., Suzuki H.

    Meeting abstracts of the Physical Society of Japan   66 ( 1 ) 45 - 45  2011.03

    CiNii

  • 21aBD-7 Analysis of the Equation of State for Hot Asymmetric Nuclear Matter with the Cluster Variational Method

    Togashi H., Kanzawa H., Takano M.

    Meeting abstracts of the Physical Society of Japan   65 ( 1 ) 47 - 47  2010.03

    CiNii

  • 21pSA-11 Extension of the equation of state for infinite nuclear matter to nonuniform matter using the Thomas-Fermi approximation IV

    Kanzawa H., Oyamatsu K., Sumiyoshi K., Takano M.

    Meeting abstracts of the Physical Society of Japan   63 ( 2 ) 37 - 37  2008.08

    CiNii

  • 24pZH-12 Extension of the equation of state for uniform nuclear matter to nonuniform matter using the Thomas-Fermi approximation III

    Kanzawa H., Oyamatsu K., Sumiyoshi K., Takano M.

    Meeting abstracts of the Physical Society of Japan   63 ( 1 ) 55 - 55  2008.02

    CiNii

  • 21pYE-13 Refinement of the equation of state for infinite nuclear matter by taking into account gross features of stable nuclei II

    Kanzawa H., Oyamatsu K., Sumiyoshi K., Takano M.

    Meeting abstracts of the Physical Society of Japan   62 ( 2 ) 37 - 37  2007.08

    CiNii

  • 28aSB-9 Refinement of the equation of state for infinite nuclear matter by taking into account gross features of stable nuclei

    Kanzawa H., Oyamatsu K., Sumiyoshi K., Takano M.

    Meeting abstracts of the Physical Society of Japan   62 ( 1 ) 49 - 49  2007.02

    CiNii

▼display all

 

Syllabus

▼display all

 

Sub-affiliation

  • Faculty of Science and Engineering   Graduate School of Advanced Science and Engineering

Research Institute

  • 2022
    -
    2024

    Waseda Research Institute for Science and Engineering   Concurrent Researcher

Internal Special Research Projects

  • 変分法によるバリオン物質状態方程式の作成とコンパクト天体への応用

    2020   富樫甫

     View Summary

    クラスター変分法により、絶対零度ハイペロン物質の1バリオン当たりのエネルギーを計算する研究において、結合チャネルを考慮する手法を考案した。すなわち、陽子、中性子、Λ、Σ-が混在する系において、この4粒子の重ね合わせの状態でありかつ互いに直交する4種類の準粒子状態を考え、系はこの4種の準粒子の多体系と考える。そして結合チャネルを考慮し、準粒子中の重ね合わせの割合は系のエネルギーを最小にするように決定する。テスト計算を行い、結合チャネルの考慮によりエネルギーが減少する妥当な結果が得られた。ただしその効果は小さく、ハイペロン星の構造には大きな影響は見られなかった。

  • エネルギー汎関数を用いた変分法による有限温度核物質状態方程式の作成

    2019   小路 薫, 富樫 甫

     View Summary

    2体核力AV6’と3体核力UIXから出発した、エネルギー汎関数を用いた変分法による、有限温度中性子物質および対称核物質の状態方程式に基づき、静的に近似した原始中性子星の構造計算を行った。現象論的3体斥力の強度は、核物質飽和点での経験値を再現するように再調整した。また非対称核物質の自由エネルギーは、対称核物質と中性子物質の自由エネルギーを陽子混在度について内挿することで決定した。加えて低密度の非一様相は、Togashi EOSを代用した。得られた冷たい中性子星の質量と半径の関係は、近年得られた中性子星観測データと矛盾せず、原始中性子星構造も妥当な振る舞いを示した。

  • エネルギー汎関数を用いた変分法による核物質状態方程式の研究

    2019   井山直哉, 不島昇士

     View Summary

    現実的核力から出発してエネルギー汎関数を用いた変分法により、有限温度核物質状態方程式を求めることを最終目標とし、静的な中心力的2体核力が相対論的ブースト効果で生じる運動量依存項を扱うように、理論の拡張を行った。その結果、相対論的ブースト効果は有意に中性子物質エネルギーを上昇させることが分かった。更にエネルギー汎関数を2粒子スピン固有状態に射影した動径分布関数の汎関数として構築する代わりに、2粒子スピンの並行・反並行で区別した動径分布関数の汎関数として構築する研究も行った。そして液体ヘリウム3の場合について、従来のエネルギーが深くなりすぎる傾向が改善されることが分かった。

  • 3体核力の不定性を考慮した有限温度核物質状態方程式の構築と原始中性子星への適用

    2018   坪田祥一, 矢野貴士

     View Summary

    現実的核力から出発して有限温度核物質状態方程式を求め、3体核力の不定性が原始中性子星構造へ与える影響を調べることを最終目的とし、そこで用いる変分法の精度向上を目指し、それを液体ヘリウム3に適用する研究を行った。まず3次元液体ヘリウム3に対しては、粒子間相関の一部を予め一粒子励起エネルギーとして取り入れる改良を試みた。そして特に液体ヘリウム4において若干の改善が見られた。さらに2次元ヘリウム3系の極低温液化問題がスピン三重項相関と関連することを検証するため、スピン偏極した有限温度3次元液体ヘリウム3系に対する変分計算を行い、スピン偏極した方が安定となる場合が生じる可能性が示された。

  • 3体核力の不定性を考慮した有限温度核物質状態方程式の構築と原始中性子星への適用

    2018   小路薫, 富樫甫

     View Summary

    本研究課題では、現実的核力から出発して有限温度核物質状態方程式を求め、原始中性子星の構造を計算し、3体核力の不定性の与える影響を調べることを目的とする。そして先行研究を発展させ、2体核力AV6'と3体核力UIXを用いた有限温度中性子物質及び対称核物質の自由エネルギーを計算した。絶対零度核物質に対する変分法を有限温度核物質へ拡張する際、Schmidt-Pandharipandeの方法を採用する。得られた自由エネルギーは密度、温度の広範囲で妥当な振る舞いを示した。ただし粒子数保存の条件の破れによって、特に低密度で数値計算が不安定になる困難が生じたが、回復長を導入することで問題解決を図った。

  • 一様核物質に対するエネルギー汎関数を用いた変分法の研究

    2017  

     View Summary

    エネルギー汎関数を用いた変分法により一様核物質の状態方程式を求める研究を推進した。絶対零度核物質の場合、2体核力としてAV6'、3体核力としてUIXを用い、対称核物質の状態方程式を求めた。状態方程式は妥当な振る舞いを示し、また一部の先行研究で予言されたπ中間子凝縮相への1次相転移は見られなかった。有限温度核物質に対しては、2体核力をAV4'、3体核力はUIX斥力成分とし、得られた状態方程式を原始中性子星構造計算へと適用した。特に3体斥力の強さの不定性の影響を調べると、3体斥力が強いと星の半径が大きくなるが、昨年観測された中性子星連星合体の重力波放出からの観測的制限と矛盾しない。

  • 有限温度一様核物資に対するエネルギー汎関数を用いた変分法の研究

    2016  

     View Summary

    現実的核力から出発して有限温度一様核物質の状態方程式を作成するための、エネルギー汎関数を用いた変分法の改良を行った。特に、3体核力としてUIX2π交換項を含んだ場合の中性子物質のエネルギー計算を行い、Akmalらの核物質状態方程式と同様なπ中間子凝縮相出現の兆候を得た。ただし彼らの予想のような1次相転移はみられなかった。また2体核力成分としてスピン・軌道力を考慮した場合の理論の改良も行い、モンテカルロ計算と矛盾しない結果を得た。さらに2体中心力およびUIX3体力斥力項までを考慮した有限温度の中性子物質および対称核物質の自由エネルギーを計算し、幅広い密度領域で安定した数値解を得た。

  • 有限温度一様核物質に対するエネルギー汎関数を用いた変分法の研究

    2015  

     View Summary

    現実的核力から出発して有限温度一様核物質の状態方程式を作成するために、2体核力として中心力、テンソル力、スピン・軌道力を含むAV8’ポテンシャルを、そして3体核力としてUIXポテンシャル斥力項を用いた場合の絶対零度中性子物質の一粒子当たりのエネルギーを、エネルギー汎関数を用いた変分法により求めた。特に従来提案していたエネルギー汎関数では十分に考慮されていなかった、スピン・軌道力項の微分演算子が粒子間相間に演算して生じる寄与を摂動論的に評価したところ、その寄与はエネルギー全体に対して十分小さいことが判明し、得られたエネルギーがモンテカルロ計算結果と良く一致することを確認した。

  • 非中心力を考慮した近似的エネルギー表式の改良と一様核物質におけるテンソル相関

    2004  

     View Summary

     一様核物質のエネルギーを求めるための、近似的エネルギー表式を用いた変分法の改良を行った。 この変分法では、一核子当たりのエネルギーを変分関数の汎関数でexplicitに表す、近似的エネルギー表式を作成する。そのエネルギー表式を用いて、変分によりEuler-Lagrange方程式を導出し、それらを解く事により十分最小化されたエネルギーを得る事が出来る。 この変分法は中心力で相互作用するフェルミ粒子系(液体ヘリウム3等)には有効であるが、現実的な一様核物質に適用した場合、2体核力の非中心力成分が不自然な振る舞いをし、変分計算結果は非常に低いエネルギーを与えてしまうとともに、非中心力型分布関数が長距離相関を持ってしまう、という問題が生じていた。これらの原因はエネルギー表式における非中心力(相関)の取り扱いの不十分さにあり、問題を解決するためには近似的エネルギー表式を改良しなければならない。しかしこの改良は非常に困難であるため、従来は現象論的な補正法を採用してきた。それに対し、本研究では第1原理的に、近似的エネルギー表式の改良を行った。特に、核力の非中心力成分に対応する代表的非中心力相関としてテンソル力相関とスピン・軌道力相関がある中で、今回はテンソル力相関が寄与するエネルギー項について、改良を行った。 一様核物質に対しJastrow型の波動関数を仮定するとハミルトニアンの期待値と近似的エネルギー表式の両者がクラスター展開できるので、各クラスター項を比較する事により、テンソル相関を含む3体クラスター項の寄与が従来のエネルギー表式に不足していた事がわかった。よって、該当するクラスター項を取り入れるような新たなエネルギー項を作成し、従来のエネルギー表式に追加した。ただし、単に3体クラスター項の部分を取り入れるようにエネルギー項を作成すると、それは変分に対して底なしになるので、さらに修正を施した表式を採用した。ここで更なる修正は、より高次のクラスター項を取り入れている事に相当するが、多少の任意性を持ってしまう。今回は、考えられ得る最も簡単な表式を採用した。 新たに提案した近似的エネルギー表式を用いた変分計算による核物質のエネルギー値は、従来の計算結果より高い値となり、改善がみられた。ただし扱う物質の状態(核子数密度、陽子混在度)によって、数値計算の不安定性が生じた。 今後の課題は、高次クラスター項を具体的に考察することによりエネルギー表式の任意性を減少させること、数値計算の不安定性の問題を解決する事、さらにスピン・軌道力型相関に対する同様の改良を進める事である。

  • スピン・アイソピン偏極を考慮した核物質に対する近似的エネルギー表式

    2002  

     View Summary

    任意にスピン偏極した中性子物質と、スピンの偏極はなく任意にアイソスピン偏極した、すなわち非対称核物質に対する近似的エネルギー表式の導出を行った。ただし2体の核力は中心力のみを仮定した。近似的エネルギー表式は状態依存の動径分布関数の汎関数として記述され、その動径分布関数を変分関数とみなして変分をとる事によりオイラー・ラグランジュ方程式が導出される。これは動径分布関数の連立微積分方程式となり、それらを数値的に解く事により、具体的なエネルギー値を、密度とスピン(またはアイソスピン)偏極度の関数として得る。中性子物質に対するスピン偏極については、スピンの偏極度の増加に伴い、中性子物質のエネルギー密度が増加する、常磁性的振る舞いが見られた。これは、従来の他の多体計算法を用いた中性子物質の磁性と矛盾しない。よって、マグネターのような超強磁場を説明する可能性として示唆されている核物質の強磁性的振る舞いは期待できない事を再確認する事となった。ただし、核力の非中心力成分や3体力の効果は今後の課題として残っている。また非対称核物質については、対称核物質から陽子混在度を減少させる事により中性子物質へと変化させるにつれて、非対称核物質のエネルギーの上昇は陽子混在度の2次に比例するように見られ、この傾向は他の多体計算結果と矛盾しない。また、その2次の係数に関連する対称エネルギーも、実験値と矛盾しない値が得られた。ただし、陽子混在度が0に近い、すなわち中性子物質に近い状態では、エネルギーの上昇の割合が陽子混在度の2次よりずれる傾向も見られた。これは陽子混在度の高次の項に対応するずれの項の存在を示唆している。この高次の項の寄与を定量的に求めるためには、さらに核力を現実的にした場合の近似的エネルギー表式の導出が必要である。

  • 液体構造関数に対する必要条件を考慮した変分法による非対称核物質の研究

    2000  

     View Summary

     スピンまたはアイソスピンが偏極したFermi粒子系における一粒子当りのエネルギーを求める新しい変分法の定式化を行った。これは近似的エネルギー表式を用いた変分法であり、一粒子当りのエネルギーを変分関数の汎関数としてexplicitに書き表す方法である。この方法の特徴は、スピン(アイソスピン)依存の液体構造関数に対して一般的に成り立つ、幾つかの必要条件が考慮されていて、変分計算の際にこれらの必要条件が自動的に満足されるように、エネルギー表式が作られている事である。これまでこの変分法は、スピンの偏極していない液体3Heや完全にスピン偏極した液体3He等を対象としていたが、今回はスピンの偏極度が任意の場合を取り扱えるように、理論を拡張した。スピンが任意に偏極した場合の液体構造関数に対する必要条件は、スピン偏極のない場合に比べて相当複雑になり、原理的に無限個の独立な必要条件が存在する。今回の研究では、それらの中で最も厳しい条件式に着目し、それらを用いた近似的エネルギー表式の作成に成功した。そしてその表式を用いた変分計算によってエネルギー値を求め、スピン偏極度と共にエネルギーがどのように変化するかを調べた。さらに核物質に対して理論を拡張し、スピンは偏極せず、代わりにアイソスピンが偏極する非対称核物質に対するエネルギー表式を作成した。現在は核力が2体の中心力である場合について理論を構築しているが、この場合について、陽子数、中性子数の比と共に、核物質のエネルギーがどのように変化するかを調べた。このエネルギー変化は、陽子数と中性子数の差の2次式で十分記述出来ると言われているが、本研究におけるpreliminaryな計算では、陽子数と中性子数の差の4次の項も無視できない結果が得られた。2体核力をより現実的なものにする等の改良によって、この4次の項の効果を詳しく調べる事が、今後の課題の一つである。

  • 非一様フェルミ粒子系に対する変分法

    1998  

     View Summary

    非一様に分布している無限に大きい核物質の絶対零度におけるエネルギー密度を、変分法によって理論的に求める研究を行った。 無限に大きい核物質や液体ヘリウムのように、強い粒子間相関を持つ一様フェルミ粒子系のエネルギー密度を求める変分計算法の研究の歴史は古く、Fermi Hypernetted Chain (FHNC) 近似等がその代表的なものである。また液体ヘリウムや電子ガスなどの場合には、非一様物質にも適用可能なFHNC法が提案されている。ところが無限に大きい核物質の場合、核力の複雑さのために、上記の非一様FHNC法をそのまま用いる事は出来ない。 そこで本研究では、FHNC法の原点となるクラスター変分法に立ち戻り、非一様核物質の場合の変分計算法の定式化を試みた。1次元の外場を導入する事によって、1次元の密度変化を考える。ただし、その軸方向±∞では、互いに密度の異なる一様物質と同じ状態になる事を境界条件とする。簡単のために、核力は中心力とする(状態依存性は考慮する)。 変分法で用いられるJastrow型試行関数は、粒子間相関が無い場合の波動関数Φと粒子間相関関数Fの積で書かれる。本研究では非一様密度分布の場合、Φとして上記の外場中の1粒子波動関数からなるスレーター行列式を用いる。Fとしては、一様物質の場合に用いられる2粒子間相関関数fだけではなく、1粒子変分関数gの積を含める。これは2粒子間の距離が十分大きい場合にfがゼロになるという、fのクラスター性を保証するためである。 この拡張されたJastrow波動関数によるハミルトニアン期待値のクラスター展開は、一様物質に対する表式より形式が複雑になる。そこでまず2体クラスター近似によるエネルギー表式を導いた。変分関数はfとgで、オイラーラグランジュ(EL)方程式は、それらの連立偏微分方程式となる。現在本研究は、EL方程式を解く数値計算の準備の段階にあるが、場合によっては、変分関数fとgの何れかをパラメータ化する必要があるかも知れない。また一様核物質の変分計算の際に必要であった構造関数に関する条件の導入も検討する必要があり、これらの点を考慮しつつ、今後更に研究を進める。

  • ボンポテンシャルを用いた一様核物質のエネルギーの変分計算

    1997  

     View Summary

     一様等方な核物質中で、核子が運動量依存性を持つ核力ポテンシャルで相互作用を及ぼしている場合の、一核子あたりのエネルギーを、近似的エネルギー表式を用いる新変分法によって求めた。 近似的エネルギー表式を用いた新変分法は、一様核物質のように、強い短距離値からで相互作用しているフェルミ粒子系に対して有効な多体計算法で、特に相互作用が中心力の場合(液体ヘリウム3など)で成功を収めている。この処方は、核力のように状態依存性が強く非中心力も無視できない、現実的核物質への適用へと拡張されているが、現段階では、拡張された新変分法の与える一核子あたりのエネルギーは、実験値より相当低くなっている。その原因の一つに、用いた現実的核力モデルの斥力芯が弱い事が考えられる。 そこで本研究では、現実的核力モデルの一つであるボンポテンシャルを用いた。ここで注目したのは、ボンポテンシャルが、これまで用いた核力モデルと異なり、運動量の2次の部分の項を含んでいることである。この項は一様核物質中において、核力の斥力芯の部分での核子のみかけの質量を小さくする働きをし、その結果effectiveに核力の斥力芯の効果を強め、全体のエネルギーを高くする事が期待される。本研究では、最も簡単な場合として、一様等方な中性子物質に対して、ボンポテンシャルの中心力部分のみを用いた変分計算と、中心力部分+運動量の2次の部分を用いた変分計算を行い、得られた一核子当たりのエネルギーを比較した。そして実際に斥力芯の効果が強まっていること、またそれに伴い一核子あたりのエネルギーが高くなっていることを確認した。 ところが、理論を対称核物質に拡張した場合、期待した斥力芯の効果が見られない事、またその原因がポテンシャル自身にある事が判明した。そこでボンポテンシャルと同様に運動量の2次の効果を持ち、さらに対称核物質においても斥力芯の効果が保証されている、パリポテンシャルを用いて同様の変分計算を行った。その結果、中性子物質、対称核物質共に、従来よりreasonableなエネルギー(状態方程式)が得られ、またそれを用いての中性子星構造計算などにおいても、観測と矛盾の無い結果が得られた。 今後の課題は、より現実的な核物質を対象として計算を行い、最終的に核力の運動量の2次の部分がどの程度有効に働くかを調べることである。またボンポテンシャル以外に、変分計算に適した、運動量の2次の部分を持つ核力ポテンシャルを用いた場合についても研究を行う。

▼display all