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Yoritaka Iwata

Publications and source records attributed to Yoritaka Iwata.

At least 37 records · Page 2Linked to original sources
arXiv2020

Solitons in nuclear time-dependent density functional theory

The soliton existence in sub-atomic many-nucleon systems is discussed. In many nucleon dynamics represented by the nuclear time-dependent density functional formalism, much attention is paid to energy and mass dependence of the soliton existence. In conclusion, the existence of nuclear soliton is clarified if the temperature of nuclear system is from 10 to 30 MeV. With respect to the mass dependence $^{4}$He and $^{16}$O are suggested to be the candidates for the self-bound states exhibiting the property of nuclear soliton.

nucl-th↗
arXiv2020

Operator topology for logarithmic infinitesimal generators

Generally-unbounded infinitesimal generators are studied in the context of operator topology. Beginning with the definition of seminorm, the concept of locally convex topological vector space is introduced as well as the concept of Fr{é}chet space. These are the basic concepts for defining an operator topology. Consequently, by associating the topological concepts with the convergence of sequence, a suitable mathematical framework for obtaining the logarithmic representation of infinitesimal generators is presented.

math.FA↗
arXiv2019

Perturbation Scheme for the Effective Nuclear Force

Based on a systematic Hartree-Fock+BCS calculation, new perturbation scheme is proposed to modify the existing Skyrme-type effective nuclear force. Much attention is paid to have a better description of fission property of heavy nuclei. In terms of incorporating the nuclear medium effects on the fission barrier height more correctly, two typical Skyrme parameter sets (SkM* and SLy4) are modified. In conclusion, according to the comparison to experiments, the calculated fission barrier heights are improved by almost 90$\%$.

nucl-th↗
arXiv2019

Unbounded formulation of the rotation group

The rotation group is formulated based on the abstract $B(X)$-module framework. Although the infinitesimal generators of rotation group include differential operators, the rotation group is formulated utilizing the framework of bounded operator algebra. In this article, unbounded formulation of rotation group is established.

math-ph↗
arXiv2019

Conditional recovery of time-reversal symmetry in many nucleus systems

Propagation of non-topological soliton in many-nucleus systems is studied based on time-dependent density functional calculations with focusing on mass and energy dependence. The dispersive property and the nonlinearity of the system, which are inherently included in the nuclear density functional, are essential factors to form a non-topological soliton. On the other hand the soliton propagation is prevented by the charge equilibration dynamics, and the competition possibly appears. In this article, based on the energy-dependence of the two competitive factors, the concept of conditional recovery of time-reversal symmetry is proposed in many nucleus systems. It clarifies a possibility of preserving nuclear medium inside natural or artificial nuclear reactors, under a suitable temperature. From an astrophysical point of view, the existence of the low-temperature solitonic core of compact stars is suggested.

nlin.PS↗
arXiv2018

Abstract formulation of the Cole-Hopf transform

Operator representation of Cole-Hopf transform is obtained based on the logarithmic representation of infinitesimal generators. For this purpose the relativistic formulation of abstract evolution equation is introduced. Even independent of the spatial dimension, the Cole-Hopf transform is generalized to a transform between linear and nonlinear equations defined in Banach spaces. In conclusion a role of transform between the evolution operator and its infinitesimal generator is understood in the context of generating nonlinear semigroup.

math.AP↗
arXiv2018

Relativistic formulation of abstract evolution equations

The relativistic formulation of abstract evolution equations is introduced. The corresponding logarithmic representation is shown to exist without assuming the invertible property of evolution operators. Consequently, by means of the logarithmic representation of operators, nonlinear and discrete properties are shown to be valid to the infinitesimal generators of relativistic abstract evolution equations.

math.AP↗
arXiv2017

Neutrino potential for neutrinoless double beta decay

Neutrino potential for neutrinoless double beta decay is studied with focusing on its statistical property. The statistics provide a gross view of understanding amplitude of constitutional components of the nuclear matrix element.

hep-ph↗
arXiv2017

Heavy neutrino potential for neutrinoless double beta decay

Heavy neutrino potential for neutrinoless double beta decay is studied with focusing on its statistical property. The existence condition for heavy neutrinos is also presented. In particular sterile neutrinos are possible candidate for heavy nuetrinos. The statistics provide a gross view of understanding amplitude of constitutional components of the nuclear matrix element.

hep-ph↗
arXiv2016

Infinitesimal generators of invertible evolution families

A logarithm representation of operators is introduced as well as a concept of pre-infinitesimal generator. Generators of invertible evolution families are represented by the logarithm representation, and a set of operators represented by the logarithm is shown to be associated with analytic semigroups. Consequently generally-unbounded infinitesimal generators of invertible evolution families are characterized by a convergent power series representation.

math.FA↗
arXiv2015

Examination of the stability of a rod-shaped structure in $^{24}$Mg

The stable existence of a six-$α$ linear structure in highly excited states of $^{24}$Mg is studied based on a systematic Cranked Hartree-Fock calculation with various Skyrme-type interactions. Its stability is examined by allowing the transition of the cluster structure to the shell-model like structure. Especially, the six-$α$ linear state is exposed to two major instabilities: the bending motion, which is the main path for the transition to low-lying states, and the spin-orbit interaction, which is the driving force to break the $α$ clusters and enhance the independent motion of the nucleons. The linear structure with large angular momentum is obtained as a meta-stable stationary state.

nucl-th↗
arXiv2015

Present Status of Fission Research Based on TDDFT

Fission resulting from collision of atomic nuclei is systematically investigated based on time-dependent density functional calculations. Time-dependent density functional theory (TDDFT) is a framework, which enables us to treat quantum many-body dynamics with nucleon degrees of freedom. In this article a theoretical framework called Composite-Nucleus Constrained TDDFT is introduced, and charge equilibrium hypothesis for collision fission dynamics is examined.

nucl-th↗
arXiv2014

Co-existence of states in quantum systems

Co-existence of different states is a profound concept, which possibly underlies the phase transition and the symmetry breaking. Because of a property inherent to quantum mechanics (cf. uncertainty), the co-existence is expected to appear more naturally in quantum-microscopic systems than in macroscopic systems. In this paper a mathematical theory describing co-existence of states in quantum systems is presented, and the co-existence is classified into 9 types.

math-ph↗
arXiv2014

Energy-dependent existence of soliton in the synthesis of chemical elements

Light chemical elements are, for instance, produced through ion collisions taking place in the core of stars, where fusion is particularly important to the synthesis of chemical elements. Meanwhile soliton provides non-interacting transparency leading to the hindrance of fusion cross section. In order to explain high fusion cross section actually observed in low incident energies, it is necessary to discover the suppression mechanism of soliton propagation. In this paper, based on a systematic three-dimensional time-dependent density functional calculation, the existence of soliton is examined for ion collisions with some incident energies, impact parameters, and nuclear force parameter sets. As a result solitons are suggested to exist highly depending on the energy. The suppression of soliton is consequently due to the spin-orbit force and the momentum-dependent components of the nuclear force.

nlin.PS↗
arXiv2013

Time-scaled scenario of low-energy heavy-ion collisions

The underlying scenario of low-energy heavy-ion collisions is presented based on time-dependent density-functional calculations. A classification of several types of reaction dynamics is given with respect to their time-scales.

nucl-th↗
arXiv2012

Fissibility of compound nuclei

Collisions between $^{248}$Cm and $^{48}$Ca are systematically investigated by time-dependent density functional calculations with evaporation prescription. Depending on the incident energy and impact parameter, fusion, deep-inelastic and fission events are expected to appear. In this paper, a microscopic method of calculating the fissibility of compound nuclei is presented.

nucl-th↗
arXiv2012

Energy density functional in nuclear physics

Fundamentals of energy density functional in nuclear physics are presented. Much attention is paid to a mathematically rigorous treatment of deriving the energy density functional. The specific features of the density functional used in studying many-nucleon systems, which is quite different from that used in many-electron systems, are also shown. The intended audience are physicists, chemists and mathematicians. In particular those who will start to study the density functional theory are intended.

nucl-th↗