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Y. Tsue

Publications and source records attributed to Y. Tsue.

At least 73 records · Page 4Linked to original sources
arXiv2004

A Possible Boson Realization of the so(4)- and the so(3,1)-Algebra

As natural extensions of the boson realizations of the su(2)- and the su(1,1)-algebra, the so(4)- and the so(3,1)-algebras are presented in the form of boson realizations with four kinds of boson operators. For each algebra, two forms are discussed. One is constructed in terms of two sets of the boson operators which play a role of spherical tensor with rank 1/2. The other is based on the ranks 1 and 0. As a possible application, the Runge-Lenz-Pauli vector, which is famous in the hydrogen atom, is derived with some aspects.

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arXiv2004

Amplification of Quantum Meson Modes in the Late Time of Chiral Phase Transition

It is shown that there exists a possibility of amplification of amplitudes of quantum pion modes with low momenta in the late time of chiral phase transition by using the Gaussian wave functional approximation in the O(4) linear sigma model. It is also shown that the amplification occurs in the mechanism of the resonance by forced oscillation as well as the parametric resonance induced by the small oscillation of the chiral condensate. These mechanisms are investigated in both the case of spatially homogeneous system and the spatially expanded system described by the Bjorken coordinate.

hep-ph↗
arXiv2004

Coupling Schemes for an n su(2) Spin System

In the framework of the Schwinger boson representation for the su(2)-algebra, the closed form is derived for the total spin eigenstates which result from the coupling of n su(2)-spins. In order to demonstrate its usefulness, the orthogonal set for the so(5)-algebra, which is reduced to four su(2)-spin systems, is obtained.

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arXiv2004

A Possible Extension of a Trial State in the TDHF Theory with Canonical Form in the Lipkin Model

With the aim of the extension of the TDHF theory in the canonical form in the Lipkin model, the trial state for the variation is constructed, which is an extension of the Slater determinant. The canonicity condition is imposed to formulate the variational approach in the canonical form. A possible solution of the canonicity condition is given and the zero-point fluctuation induced by the uncertainty principle is investigated. As an application, the ground state energy is evaluated.

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arXiv2004

Fermionic Squeezed State for Simple Algebraic Models in Many-Fermion Systems

It is shown that a variational approach with fermionic squeezed states to many-fermion systems such as pairing model is one of useful methods beyond the usual Hartree-Fock-Bogoliubov approximation. A pairing-type quasi-spin squeezed state is constructed and adopted as a trial state in the variational method. By using this state, quantum fluctuations are taken into account. In pairing model, dynamical and static approaches are discussed in the context of comparing with the Hartree-Fock-Bogoliubov approximation about ground state energy. As a possible extension to the O(4) model, prospective squeezed states are investigated and the usefulness is discussed.

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arXiv2004

Deformed Boson Scheme Stressing Even-Odd Boson Number Difference. III

A basic idea is proposed for extending the formalism of Part (II) of the series of our paper to the case of the parameter-dependent deformation. It is stressed that, through this extension, the variety of the application increases. Further, an answer for the problem mentioned in Part (II) is presented.

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arXiv2003

Deformed Boson Scheme Stressing Even-Odd Boson Number Difference. II

The boson-pair coherent state developed in Part (I) is generalized to the case in which the state is a mixture of even-boson and odd-boson number states. A general framework is shown and its three concrete examples are discussed. Main idea is in the application of the deformed boson scheme presented by the present authors.

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arXiv2003

Deformed Boson Scheme Stressing Even-Odd Boson Number Difference. I

An idea of the deformed boson scheme developed by the present authors is applied to the case of boson-pair coherent state. In this state, even and odd boson number difference is stressed and various concrete examples of the boson-pair coherent states are shown. Concerning some of them, mutual relations are investigated in connection to the su(1,1)-algebra. A formulation in terms of the MYT boson mapping is also performed.

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arXiv2003

Variational Approach to the Dynamics of Bose-Einstein Condensates.I --Variational Ansatz and Quantum Dynamics--

Variational method is applied to describe Bose-Einstein condensates (BEC) interacting via a pseudo-potential, taking into account quantum fluctuations around the mean field by the Gaussian approximation. Contributions from the pair-wise scattering by the singular potential should be removed carefully to avoid double countings in the perturbation series in terms of original bare interaction. We show that this procedure removes all dangerous terms which contain divergences.

cond-mat↗
arXiv2003

Note on the Orthogonal Set in Six Kinds of Boson Operators --In Relation to the su(1,1)- and its Relevant Algebras--

Following the basic idea proposed by the present authors in recent paper, a possible form of the orthogonal set for many-body system consisting of six kinds of boson operators is developed. In contrast to the recent paper, in which the su(2)-algebra plays a central role, in this paper, the su(1,1)-algebra is in a central position. The orthogonal set obtained in this paper is expressed in terms of monomial with respect to the state generating operators.

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arXiv2003

On the Boson Number Operator in the Deformed Boson Scheme

Concerning the energy of harmonic oscillator, a prescription is proposed for making the original form unchanged even after q-deformation. Applicability of the prescription is limited, but, it can be applied to various cases which are well known.

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arXiv2002

Time-Evolution of Collective Meson Fields and Amplification of Quantum Meson Modes in Chiral Phase Transition

The time evolution of quantum meson fields in the O(4) linear sigma model is investigated in a context of the dynamical chiral phase transition. It is shown that amplitudes of quantum pion modes are amplified due to both mechanisms of a parametric resonance and a resonance by the forced oscillation according to the small oscillation of the chiral condensate in the late time of chiral phase transition.

hep-ph↗
arXiv2002

The su(1,1)-Algebraic Boson Model in the Deformed Boson Scheme

Following the deformed boson scheme leading to the su(1,1)-algebra, a certain simple boson system is deformed in the framework of the second Holstein-Primakoff representation. With the aid of the MYT boson mapping, the second representation arrives at the first Holstein-Primakoff representation. The su(1,1)-algebraic model obtained in this procedure is compared with that in the Schwinger representation investigated by three of the present authors (A.K., Y.T. and M.Y.).

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arXiv2002

Note on the Deformed Boson Scheme in Four Kinds of Boson Operators

The deformed boson scheme in four kinds of boson operators, which was recently proposed by the present authors, is supplemented by the T-type deformation closely related with the su(1,1)-algebra. Two subjects are discussed in relation to the S-type deformation closely related with the su(2)-algebra.

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arXiv2002

Deformed Boson Scheme including Conventional q-Deformation in Time-Dependent Variational Method. IV

Basic idea presented in Parts (I)-(III) for the deformed boson scheme is applied to the case of the su(2)- and su(1,1)-algebras for describing many-body systems consisting of four kinds of boson operators. A possible form of the coherent state given by the present authors is generalized and the su(2)_q- and the su(1,1)_q-algebras are obtained in the form expressed in terms of four kinds of boson operators. As an illustrative example of the application, the framework for describing thermal effects observed in two-level shell model under the pairing correlation is proposed.

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