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Papers by Tetsuyuki Yukawa

Research paper thumbnail of Statistical Theory of Level Fluctuations : Part II. Quantal Aspects : New Trends in Chaotic Dynamics of Hamiltonian Systems

Progress of Theoretical Physics Supplement, Oct 31, 1989

Research paper thumbnail of Statistical Theory of Level Fluctuations (New Trends in Chaotic Dynamics of Hamiltonian Systems) -- (Quantal Aspects)

Progress of Theoretical Physics, Oct 1, 1989

Research paper thumbnail of Classical Solution of Two Dimensional R2-Gravity and Semiclassical Analysis (弦理論と量子重力の課題)

素粒子論研究, Dec 20, 1994

Two dimensional quantum R2-gravity and its phase structure are examined in the semiclassical appr... more Two dimensional quantum R2-gravity and its phase structure are examined in the semiclassical approach and compared with the results of the numerical simulation. Three phases are succinctly characterized by the effective action. A classical solution of the R2-Liouville equation is obtained by use of the solution of the ordinary Liouville equation. The partition function is obtained analytically. A total derivative term (surface term) plays an important role there. It is shown that the classical solution can sufficiently account for the cross-over transition of the surface property seen in the numerical simulation.

Research paper thumbnail of Phase Structure of Four-Dimensional Simplicial Quantum Gravity with a U(1) Gauge Field

Progress of Theoretical and Experimental Physics, Nov 1, 2001

The phase structure of four-dimensional simplicial quantum gravity coupled to U (1) gauge fields ... more The phase structure of four-dimensional simplicial quantum gravity coupled to U (1) gauge fields has been studied using Monte-Carlo simulations. The smooth phase is found in the intermediate region between the crumpled phase and the branched polymer phase. This new phase has a negative string susceptibility exponent, even if the number of vector fields (N V) is 1. The phase transition between the crumpled phase and the smooth phase has been studied by a finite size scaling method. From the numerical results, we expect that this model (coupled to one gauge field) has a higher order phase transition than first order, which means the possibility to take the continuum limit at the critical point. Furthermore, we consider a modification of the balls-in-boxes model for a clear understanding of the relation between the numerical results and the analytical one.

Research paper thumbnail of Grand-canonical simulation of 4D simplicial quantum gravity

Nuclear physics, May 1, 2003

A thorough numerical examination for the field theory of 4D quantum gravity (QG) with a special e... more A thorough numerical examination for the field theory of 4D quantum gravity (QG) with a special emphasis on the conformal mode dependence has been studied. More clearly than before, we obtain the string susceptibility exponent of the partition function by using the Grand-Canonical Monte-Carlo method. Taking thorough care of the update method, the simulation is made for 4D Euclidean simplicial manifold coupled to NX scalar fields and NA U(1) gauge fields. The numerical results suggest that 4D simplicial quantum gravity (SQG) can be reached to the continuum theory of 4D QG. We discuss the significant property of 4D SQG.

Research paper thumbnail of Landau Damping

Research paper thumbnail of 数値的量子重力(1996年度九州地区地域研究会:量子重力と量子宇宙論,地域スクール報告)

重力場の量子化は素粒子論に残された最も基本的な問題の一つである。大げさに言えばそれは宇宙の始まりや、自然界のすべての力の統一に本質的な関わりを持つと考えられるからである。この問題の困難さは、本質... more 重力場の量子化は素粒子論に残された最も基本的な問題の一つである。大げさに言えばそれは宇宙の始まりや、自然界のすべての力の統一に本質的な関わりを持つと考えられるからである。この問題の困難さは、本質的に非摂動的なところにある。最近、時空を格子状に分割することにより、非摂動的な量子化を数値的に実行する研究が盛んに行われている。その現状と問題点を紹介する

Research paper thumbnail of 運動の集団性(Beyond Time Dependent Hartree-Fock Theory,核内運動モードの集団性,研究会報告)

Soryushiron Kenkyu Electronics, 1984

Research paper thumbnail of Fermi liquid theory for finite systems

Nuclear Physics A, 1983

The Landau theory of Fermi liquids is reformulated in order to apply it to finite systems. A syst... more The Landau theory of Fermi liquids is reformulated in order to apply it to finite systems. A systematic truncation scheme is presented restricting the multipolarity of the Fermi surface distortion from the local equilibrium ``vacuum''. The lowest truncation scheme gives the classical fluid-dynamical equation of first sound. Including the quadrupole distortion the set of equations agrees with the fluid dynamics of ``zero'' sound. In the higher truncation scheme the set of equations involves additional tensor fields.

Research paper thumbnail of Landau damping in normal Fermi liquids at zero temperature

Il Nuovo Cimento A, 1985

SummaryAnalytical properties of dispersion equations in the Landau theory of Fermi liquid and its... more SummaryAnalytical properties of dispersion equations in the Landau theory of Fermi liquid and its quantum extension (the linearized time-dependent Hartree-Fock theory) are studied. We find that there does not appear Landau damping solution in the Landau theory with one Landau parameterF0. On the other hand, the quantum theory has complex zeros in dispersion functions for weak repulsive interactions. Calculation of the strength function exhibits a pronounced resonance peak corresponding to Landau damping of the zero sound.RiassuntoSi studiano le proprietà analitiche delle equazioni di dispersione nella teoria di Landau del liquido di Fermi e la sua estensione quantistica (la teoria linearizzata di Hartree-Fock dipendente dal tempo). Si trova che non compaiono soluzioni di smorzamento di Landau nella teoria di Landau con un parametro di LandauF0. D'altra parte, la teoria quantica ha zeri complessi nelle funzioni di dispersione per interazioni deboli repulsive. Il calcolo della funzione di forza mostra un marcato picco di risonanza che corrisponde allo smorzamento di Landau del suono nullo.РезюмеИсследуются аналитические свойства дисперсионных уравнений в теории Ландау Ферми-жидкости и ее квантовом обобщении (линеаризованная зависищая от времени теория Хартри-Фока). Получено, что в теории Ландау с одним параметром ЛандауF0 не возникает решения с затуханием Ландау, с другой стороны квантовая теория имеет комплексные нули в дисперсионных функциях для слабых взаимодействий отталкивания. Вычисление силовой функции обнаруживает явно выраженный пик, соответствующий затуханию Ландау для нулевого звука.

Research paper thumbnail of Torus self-organizing map for genome informatics

Research paper thumbnail of Meeting on Few-body Problems in High- and Medium-energy Physics

Research paper thumbnail of Quantum Chaos : Motion of energy levels of isolated systems and quasi-energy spectra of periodically kicked systems

ABSTRACT この論文は国立情報学研究所の電子図書館事業により電子化されました。

Research paper thumbnail of Strings in Computer

Complex structures are determined for surfaces with S2S^2S2 and T2T^2T2 topologies generated by the d... more Complex structures are determined for surfaces with S2S^2S2 and T2T^2T2 topologies generated by the dynamical triangulation method. For a surface with S2S^2S2 topology the spacial distribution of the conformal mode is obtained, while for the case of T2T^2T2 topology the distribution of the moduli parameter is calculated. It is also shown that the network of Feynman diagrams of massive phi3\phi^3phi3 scalar theory has a unique complex structure. This gives a numerical justification of the hadronic string model for explaining the n-particle dual amplitude.

Research paper thumbnail of Sound wave propagation in a two-component fermi liquid

Research paper thumbnail of Landau damping in the degenerate Fermi liquid

Physics Letters B, 1983

We study the dispersion law of sound propagation in the degenerate Fermi liquid. In contrast with... more We study the dispersion law of sound propagation in the degenerate Fermi liquid. In contrast with the Landau theory at zero temperature we find the damped oscillation mode (Landau damping) due to quantum effects. The relation between the frequency and the wtdth of this mode has a similar character as found in giant resonances.

Research paper thumbnail of An alpha-cluster model calculation of 12C

Physics Letters B, 1970

ABSTRACT Energy expection values of 12C have been calculated using Brink's formalism of t... more ABSTRACT Energy expection values of 12C have been calculated using Brink's formalism of the alpha-cluster model. The results suggest that a molecular-like structure is favorable for the low-lying states of 12C.

Research paper thumbnail of A shell-model theory of complex collisions

Nuclear Physics A, 1972

ABSTRACT A microscopic theory of heavy-ion reactions is proposed based on the assumption that the... more ABSTRACT A microscopic theory of heavy-ion reactions is proposed based on the assumption that the set of antisymmetrizsd products of shell-model wave functions spans the complete Hilbert space of the system. The many-body Schrödinger equation and the equations given by the scattering theory of Ekstein are represented by the basis set, fully taking the Pauli principle into account. A set of coupled equations, which resembles that of the generator coordinate method, is obtained and reduced to a set of coupled integro-differential equations which leads to a simple physical picture for the scattering process of complex particles. The interactions between composite particles which have direct relations to the T-matrices for elastic, inelastic and rearrangement collisions are expressed in terms of shell-model 16O + 16O wave functions and the nucleon-nucleon interaction. A simple example is given for the local potential to lowest order. Work supported in part by the National Science Foundation.

Research paper thumbnail of Landau theory of Fermi liquids and nuclear fluid dynamics

Nuclear Physics A, 1981

ABSTRACT Truncation schemes of Landau's equation for the distribution function in phase s... more ABSTRACT Truncation schemes of Landau's equation for the distribution function in phase space are formulated which lead to closed sets of fluid-dynamical equations. It is shown that restricting the multipolarity of the Fermi surface distortion to l ⩽ 2 is equivalent to the fluid-dynamical set obtained from a generalized scaling approximation. The l ⩽ 3 truncation is presented together with a comparison of various longitudinal and transverse sound velocities.

Research paper thumbnail of Lotka–Volterra systems integrable in quadratures

Journal of Mathematical Physics, 2008

Research paper thumbnail of Statistical Theory of Level Fluctuations : Part II. Quantal Aspects : New Trends in Chaotic Dynamics of Hamiltonian Systems

Progress of Theoretical Physics Supplement, Oct 31, 1989

Research paper thumbnail of Statistical Theory of Level Fluctuations (New Trends in Chaotic Dynamics of Hamiltonian Systems) -- (Quantal Aspects)

Progress of Theoretical Physics, Oct 1, 1989

Research paper thumbnail of Classical Solution of Two Dimensional R2-Gravity and Semiclassical Analysis (弦理論と量子重力の課題)

素粒子論研究, Dec 20, 1994

Two dimensional quantum R2-gravity and its phase structure are examined in the semiclassical appr... more Two dimensional quantum R2-gravity and its phase structure are examined in the semiclassical approach and compared with the results of the numerical simulation. Three phases are succinctly characterized by the effective action. A classical solution of the R2-Liouville equation is obtained by use of the solution of the ordinary Liouville equation. The partition function is obtained analytically. A total derivative term (surface term) plays an important role there. It is shown that the classical solution can sufficiently account for the cross-over transition of the surface property seen in the numerical simulation.

Research paper thumbnail of Phase Structure of Four-Dimensional Simplicial Quantum Gravity with a U(1) Gauge Field

Progress of Theoretical and Experimental Physics, Nov 1, 2001

The phase structure of four-dimensional simplicial quantum gravity coupled to U (1) gauge fields ... more The phase structure of four-dimensional simplicial quantum gravity coupled to U (1) gauge fields has been studied using Monte-Carlo simulations. The smooth phase is found in the intermediate region between the crumpled phase and the branched polymer phase. This new phase has a negative string susceptibility exponent, even if the number of vector fields (N V) is 1. The phase transition between the crumpled phase and the smooth phase has been studied by a finite size scaling method. From the numerical results, we expect that this model (coupled to one gauge field) has a higher order phase transition than first order, which means the possibility to take the continuum limit at the critical point. Furthermore, we consider a modification of the balls-in-boxes model for a clear understanding of the relation between the numerical results and the analytical one.

Research paper thumbnail of Grand-canonical simulation of 4D simplicial quantum gravity

Nuclear physics, May 1, 2003

A thorough numerical examination for the field theory of 4D quantum gravity (QG) with a special e... more A thorough numerical examination for the field theory of 4D quantum gravity (QG) with a special emphasis on the conformal mode dependence has been studied. More clearly than before, we obtain the string susceptibility exponent of the partition function by using the Grand-Canonical Monte-Carlo method. Taking thorough care of the update method, the simulation is made for 4D Euclidean simplicial manifold coupled to NX scalar fields and NA U(1) gauge fields. The numerical results suggest that 4D simplicial quantum gravity (SQG) can be reached to the continuum theory of 4D QG. We discuss the significant property of 4D SQG.

Research paper thumbnail of Landau Damping

Research paper thumbnail of 数値的量子重力(1996年度九州地区地域研究会:量子重力と量子宇宙論,地域スクール報告)

重力場の量子化は素粒子論に残された最も基本的な問題の一つである。大げさに言えばそれは宇宙の始まりや、自然界のすべての力の統一に本質的な関わりを持つと考えられるからである。この問題の困難さは、本質... more 重力場の量子化は素粒子論に残された最も基本的な問題の一つである。大げさに言えばそれは宇宙の始まりや、自然界のすべての力の統一に本質的な関わりを持つと考えられるからである。この問題の困難さは、本質的に非摂動的なところにある。最近、時空を格子状に分割することにより、非摂動的な量子化を数値的に実行する研究が盛んに行われている。その現状と問題点を紹介する

Research paper thumbnail of 運動の集団性(Beyond Time Dependent Hartree-Fock Theory,核内運動モードの集団性,研究会報告)

Soryushiron Kenkyu Electronics, 1984

Research paper thumbnail of Fermi liquid theory for finite systems

Nuclear Physics A, 1983

The Landau theory of Fermi liquids is reformulated in order to apply it to finite systems. A syst... more The Landau theory of Fermi liquids is reformulated in order to apply it to finite systems. A systematic truncation scheme is presented restricting the multipolarity of the Fermi surface distortion from the local equilibrium ``vacuum''. The lowest truncation scheme gives the classical fluid-dynamical equation of first sound. Including the quadrupole distortion the set of equations agrees with the fluid dynamics of ``zero'' sound. In the higher truncation scheme the set of equations involves additional tensor fields.

Research paper thumbnail of Landau damping in normal Fermi liquids at zero temperature

Il Nuovo Cimento A, 1985

SummaryAnalytical properties of dispersion equations in the Landau theory of Fermi liquid and its... more SummaryAnalytical properties of dispersion equations in the Landau theory of Fermi liquid and its quantum extension (the linearized time-dependent Hartree-Fock theory) are studied. We find that there does not appear Landau damping solution in the Landau theory with one Landau parameterF0. On the other hand, the quantum theory has complex zeros in dispersion functions for weak repulsive interactions. Calculation of the strength function exhibits a pronounced resonance peak corresponding to Landau damping of the zero sound.RiassuntoSi studiano le proprietà analitiche delle equazioni di dispersione nella teoria di Landau del liquido di Fermi e la sua estensione quantistica (la teoria linearizzata di Hartree-Fock dipendente dal tempo). Si trova che non compaiono soluzioni di smorzamento di Landau nella teoria di Landau con un parametro di LandauF0. D'altra parte, la teoria quantica ha zeri complessi nelle funzioni di dispersione per interazioni deboli repulsive. Il calcolo della funzione di forza mostra un marcato picco di risonanza che corrisponde allo smorzamento di Landau del suono nullo.РезюмеИсследуются аналитические свойства дисперсионных уравнений в теории Ландау Ферми-жидкости и ее квантовом обобщении (линеаризованная зависищая от времени теория Хартри-Фока). Получено, что в теории Ландау с одним параметром ЛандауF0 не возникает решения с затуханием Ландау, с другой стороны квантовая теория имеет комплексные нули в дисперсионных функциях для слабых взаимодействий отталкивания. Вычисление силовой функции обнаруживает явно выраженный пик, соответствующий затуханию Ландау для нулевого звука.

Research paper thumbnail of Torus self-organizing map for genome informatics

Research paper thumbnail of Meeting on Few-body Problems in High- and Medium-energy Physics

Research paper thumbnail of Quantum Chaos : Motion of energy levels of isolated systems and quasi-energy spectra of periodically kicked systems

ABSTRACT この論文は国立情報学研究所の電子図書館事業により電子化されました。

Research paper thumbnail of Strings in Computer

Complex structures are determined for surfaces with S2S^2S2 and T2T^2T2 topologies generated by the d... more Complex structures are determined for surfaces with S2S^2S2 and T2T^2T2 topologies generated by the dynamical triangulation method. For a surface with S2S^2S2 topology the spacial distribution of the conformal mode is obtained, while for the case of T2T^2T2 topology the distribution of the moduli parameter is calculated. It is also shown that the network of Feynman diagrams of massive phi3\phi^3phi3 scalar theory has a unique complex structure. This gives a numerical justification of the hadronic string model for explaining the n-particle dual amplitude.

Research paper thumbnail of Sound wave propagation in a two-component fermi liquid

Research paper thumbnail of Landau damping in the degenerate Fermi liquid

Physics Letters B, 1983

We study the dispersion law of sound propagation in the degenerate Fermi liquid. In contrast with... more We study the dispersion law of sound propagation in the degenerate Fermi liquid. In contrast with the Landau theory at zero temperature we find the damped oscillation mode (Landau damping) due to quantum effects. The relation between the frequency and the wtdth of this mode has a similar character as found in giant resonances.

Research paper thumbnail of An alpha-cluster model calculation of 12C

Physics Letters B, 1970

ABSTRACT Energy expection values of 12C have been calculated using Brink's formalism of t... more ABSTRACT Energy expection values of 12C have been calculated using Brink's formalism of the alpha-cluster model. The results suggest that a molecular-like structure is favorable for the low-lying states of 12C.

Research paper thumbnail of A shell-model theory of complex collisions

Nuclear Physics A, 1972

ABSTRACT A microscopic theory of heavy-ion reactions is proposed based on the assumption that the... more ABSTRACT A microscopic theory of heavy-ion reactions is proposed based on the assumption that the set of antisymmetrizsd products of shell-model wave functions spans the complete Hilbert space of the system. The many-body Schrödinger equation and the equations given by the scattering theory of Ekstein are represented by the basis set, fully taking the Pauli principle into account. A set of coupled equations, which resembles that of the generator coordinate method, is obtained and reduced to a set of coupled integro-differential equations which leads to a simple physical picture for the scattering process of complex particles. The interactions between composite particles which have direct relations to the T-matrices for elastic, inelastic and rearrangement collisions are expressed in terms of shell-model 16O + 16O wave functions and the nucleon-nucleon interaction. A simple example is given for the local potential to lowest order. Work supported in part by the National Science Foundation.

Research paper thumbnail of Landau theory of Fermi liquids and nuclear fluid dynamics

Nuclear Physics A, 1981

ABSTRACT Truncation schemes of Landau's equation for the distribution function in phase s... more ABSTRACT Truncation schemes of Landau's equation for the distribution function in phase space are formulated which lead to closed sets of fluid-dynamical equations. It is shown that restricting the multipolarity of the Fermi surface distortion to l ⩽ 2 is equivalent to the fluid-dynamical set obtained from a generalized scaling approximation. The l ⩽ 3 truncation is presented together with a comparison of various longitudinal and transverse sound velocities.

Research paper thumbnail of Lotka–Volterra systems integrable in quadratures

Journal of Mathematical Physics, 2008