Kazuo Kitahara - Academia.edu (original) (raw)

Papers by Kazuo Kitahara

Research paper thumbnail of Superradiance and Dipole Ordering of an N Two-Level System Interacting with Optical Near Fields

Journal of The Physical Society of Japan, 2003

A model is presented for a system of N two-level excitons interacting with each other via optical... more A model is presented for a system of N two-level excitons interacting with each other via optical near fields represented as localized photons. In a low exciton density limit, quantum dynamics of the dipole moments or quantum coherence between any two energy levels is linear. As the exciton density becomes higher, the dynamics becomes nonlinear, and the system has several kinds of quasi-steady states of the dipole distribution depending on the system parameters. These quasi-steady states are classified with the help of the effective Hamiltonian that is derived from the renormalization of degrees of freedom of localized photons with a unitary transformation. Among them there exist a “ferromagnetic” state (dipole-ordered state), in which all electric dipoles are aligned in the same direction, and an “anti-ferromagnetic” state, where all dipoles alternatingly change the direction. In addition, we show that an arbitrary state can be transformed into a dipole-ordered state by manipulating initial values of the population differences appropriately. For example, if we initially prepare a dipole-forbidden state, which is similar to the “anti-ferromagnetic” state and cannot be coupled with propagating far fields, and if we manipulate the distribution of the population differences properly, the initial state evolves into a dipole-ordered state. The radiation property of such dipole-ordered states is examined in detail. Neglecting energy dissipation by radiation, we find that some of the ordered states show strong radiation equivalent to Dicke’s superradiance. Then by introducing a radiation reservoir, the dissipative master equation is derived. Solving the equation with and without quantum correlations, we numerically show that multiple peaks in the radiation profile can survive in both cases. The mechanism of this phenomenon is discussed, and a brief comment on an application to photonic devices on a nanometer scale is given.

Research paper thumbnail of Fluctuations and the onset of instabilities in nonequilibrium systems

Physics Letters A, 1974

A nonlinear master equation describing the nucleation of critical fluctuations leading to an inst... more A nonlinear master equation describing the nucleation of critical fluctuations leading to an instability and subsequently to a dissipative structure is derived. It is suggested that the formation of these structures bears strong analogies with first order phase transitions.

Research paper thumbnail of Nonequilibrium thermodynamics of multicomponent systems

Physica A-statistical Mechanics and Its Applications, 1996

A general formalism of nonequilibrium thermodynamics of multicomponent fluids is given. Reversibl... more A general formalism of nonequilibrium thermodynamics of multicomponent fluids is given. Reversible parts of balance equations for the extensive variables are constructed in such a way that the growth rate of the extensive variables are related to their conjugate intensive parameters in an antisymmetric manner. This enables us to give the balance equation for the diffusional flow which plays an important role in the study of superfluidity and complex fluids.

Research paper thumbnail of The onset of instabilities in nonequilibrium systems

Journal of Statistical Physics, 1976

The nonlinear master equation previously proposed by Malek-Mansour and Nicolis is applied to the ... more The nonlinear master equation previously proposed by Malek-Mansour and Nicolis is applied to the analysis of unstable transitions leading to temporally or spatially organized patterns. Thecorrelation length of the destabilizing fluctuations is determined, and a number of striking analogies with equilibrium phase transitions are pointed out.

Research paper thumbnail of A derivation and comparison of two equations (Landau-Ginzburg and Cahn) for the kinetics of phase transitions

Chemical Physics, 1976

We postulate a master equation and derive by path integral methods the Cahn equation for the most... more We postulate a master equation and derive by path integral methods the Cahn equation for the most probable evolution of a nonuniform system. To do so we need to impose a constraint of local conservation of the variable of interest. The same derivation without this constraint has been shown previously to lead to a Landau-Ginzburg equation. Thus the two equations

Research paper thumbnail of On the path integral representation of stochastic processes

Journal of Statistical Physics, 1976

We derive the path integral representation of the conditional probability for a Markovian process... more We derive the path integral representation of the conditional probability for a Markovian process starting from the master equation. Existing derivations require both the variable and the transition probability to be extensive. We show that this requirement may be relaxed if Langer's formula for the transition probability is used. We prove that different path integral representations appearing in the literature are in fact equivalent and correspond to various choices of an arbitrary parameter.

Research paper thumbnail of Stochastic theory of the kinetics of phase transitions

Chemical Physics, 1976

We present a stochastic theory of the kinetics of phase transitions in univariant, nonuniform sys... more We present a stochastic theory of the kinetics of phase transitions in univariant, nonuniform systems. We assume a master equation and a relation of the transition probability to the free energy [J. S. Langer, Ann. Phys. (N.Y) 65, 53 (1971)]. The free energy is taken to be of the Cahn-Hilliard form. By means of path integral methods we obtain a

Research paper thumbnail of Coherent and diffusional motion of a chemisorbed atom

Chemical Physics Letters, 1976

Research paper thumbnail of A derivation and comparison of two equations (Landau-Ginzburg and Cahn) for the kinetics of phase transitions

Chemical Physics, 1976

We postulate a master equation and derive by path integral methods the Cahn equation for the most... more We postulate a master equation and derive by path integral methods the Cahn equation for the most probable evolution of a nonuniform system. To do so we need to impose a constraint of local conservation of the variable of interest. The same derivation without this constraint has been shown previously to lead to a Landau-Ginzburg equation. Thus the two equations

Research paper thumbnail of On the path integral representation of stochastic processes

Journal of Statistical Physics, 1976

We derive the path integral representation of the conditional probability for a Markovian process... more We derive the path integral representation of the conditional probability for a Markovian process starting from the master equation. Existing derivations require both the variable and the transition probability to be extensive. We show that this requirement may be relaxed if Langer's formula for the transition probability is used. We prove that different path integral representations appearing in the literature are in fact equivalent and correspond to various choices of an arbitrary parameter.

Research paper thumbnail of Stochastic theory of the kinetics of phase transitions

Chemical Physics, 1976

We present a stochastic theory of the kinetics of phase transitions in univariant, nonuniform sys... more We present a stochastic theory of the kinetics of phase transitions in univariant, nonuniform systems. We assume a master equation and a relation of the transition probability to the free energy [J. S. Langer, Ann. Phys. (N.Y) 65, 53 (1971)]. The free energy is taken to be of the Cahn-Hilliard form. By means of path integral methods we obtain a

Research paper thumbnail of Coherent and diffusional motion of a chemisorbed atom

Chemical Physics Letters, 1976

Research paper thumbnail of Molecular dynamics simulations of nonequilibrium spatial correlations in a reaction diffusion system

Physica A-statistical Mechanics and Its Applications, 1994

In this paper we discuss the influence of nonequilibrium effects on the rate of a thermally activ... more In this paper we discuss the influence of nonequilibrium effects on the rate of a thermally activated, exothermic reaction. The system with a binary process A A B B + ⇔ + +{ } energy is considered as an example, on which we compare molecular dynamics simulations with a simple phenomenology based on the assumption that a nonequilibrium state can be characterized by many time dependent temperatures. A good agreement between results of both methods is observed. We have found that the rate constants are changed significantly by the nonequilibrium effects, which affects system's evolution.

Research paper thumbnail of The Possibility of Controlling Spin States of Surface Beam by Electromagnetic Waves on the Surface of Dielectrics

Electromagnetic waves in vacuum is transverse. However, the evanescent light can produce spatiall... more Electromagnetic waves in vacuum is transverse. However, the evanescent light can produce spatially alternative pattern of liearly polarized light and cir cularly polarized light.

Research paper thumbnail of Superradiance and Dipole Ordering of an N Two-Level System Interacting with Optical Near Fields

Journal of The Physical Society of Japan, 2003

A model is presented for a system of N two-level excitons interacting with each other via optical... more A model is presented for a system of N two-level excitons interacting with each other via optical near fields represented as localized photons. In a low exciton density limit, quantum dynamics of the dipole moments or quantum coherence between any two energy levels is linear. As the exciton density becomes higher, the dynamics becomes nonlinear, and the system has several kinds of quasi-steady states of the dipole distribution depending on the system parameters. These quasi-steady states are classified with the help of the effective Hamiltonian that is derived from the renormalization of degrees of freedom of localized photons with a unitary transformation. Among them there exist a “ferromagnetic” state (dipole-ordered state), in which all electric dipoles are aligned in the same direction, and an “anti-ferromagnetic” state, where all dipoles alternatingly change the direction. In addition, we show that an arbitrary state can be transformed into a dipole-ordered state by manipulating initial values of the population differences appropriately. For example, if we initially prepare a dipole-forbidden state, which is similar to the “anti-ferromagnetic” state and cannot be coupled with propagating far fields, and if we manipulate the distribution of the population differences properly, the initial state evolves into a dipole-ordered state. The radiation property of such dipole-ordered states is examined in detail. Neglecting energy dissipation by radiation, we find that some of the ordered states show strong radiation equivalent to Dicke’s superradiance. Then by introducing a radiation reservoir, the dissipative master equation is derived. Solving the equation with and without quantum correlations, we numerically show that multiple peaks in the radiation profile can survive in both cases. The mechanism of this phenomenon is discussed, and a brief comment on an application to photonic devices on a nanometer scale is given.

Research paper thumbnail of Fluctuations and the onset of instabilities in nonequilibrium systems

Physics Letters A, 1974

A nonlinear master equation describing the nucleation of critical fluctuations leading to an inst... more A nonlinear master equation describing the nucleation of critical fluctuations leading to an instability and subsequently to a dissipative structure is derived. It is suggested that the formation of these structures bears strong analogies with first order phase transitions.

Research paper thumbnail of Nonequilibrium thermodynamics of multicomponent systems

Physica A-statistical Mechanics and Its Applications, 1996

A general formalism of nonequilibrium thermodynamics of multicomponent fluids is given. Reversibl... more A general formalism of nonequilibrium thermodynamics of multicomponent fluids is given. Reversible parts of balance equations for the extensive variables are constructed in such a way that the growth rate of the extensive variables are related to their conjugate intensive parameters in an antisymmetric manner. This enables us to give the balance equation for the diffusional flow which plays an important role in the study of superfluidity and complex fluids.

Research paper thumbnail of The onset of instabilities in nonequilibrium systems

Journal of Statistical Physics, 1976

The nonlinear master equation previously proposed by Malek-Mansour and Nicolis is applied to the ... more The nonlinear master equation previously proposed by Malek-Mansour and Nicolis is applied to the analysis of unstable transitions leading to temporally or spatially organized patterns. Thecorrelation length of the destabilizing fluctuations is determined, and a number of striking analogies with equilibrium phase transitions are pointed out.

Research paper thumbnail of A derivation and comparison of two equations (Landau-Ginzburg and Cahn) for the kinetics of phase transitions

Chemical Physics, 1976

We postulate a master equation and derive by path integral methods the Cahn equation for the most... more We postulate a master equation and derive by path integral methods the Cahn equation for the most probable evolution of a nonuniform system. To do so we need to impose a constraint of local conservation of the variable of interest. The same derivation without this constraint has been shown previously to lead to a Landau-Ginzburg equation. Thus the two equations

Research paper thumbnail of On the path integral representation of stochastic processes

Journal of Statistical Physics, 1976

We derive the path integral representation of the conditional probability for a Markovian process... more We derive the path integral representation of the conditional probability for a Markovian process starting from the master equation. Existing derivations require both the variable and the transition probability to be extensive. We show that this requirement may be relaxed if Langer's formula for the transition probability is used. We prove that different path integral representations appearing in the literature are in fact equivalent and correspond to various choices of an arbitrary parameter.

Research paper thumbnail of Stochastic theory of the kinetics of phase transitions

Chemical Physics, 1976

We present a stochastic theory of the kinetics of phase transitions in univariant, nonuniform sys... more We present a stochastic theory of the kinetics of phase transitions in univariant, nonuniform systems. We assume a master equation and a relation of the transition probability to the free energy [J. S. Langer, Ann. Phys. (N.Y) 65, 53 (1971)]. The free energy is taken to be of the Cahn-Hilliard form. By means of path integral methods we obtain a

Research paper thumbnail of Coherent and diffusional motion of a chemisorbed atom

Chemical Physics Letters, 1976

Research paper thumbnail of A derivation and comparison of two equations (Landau-Ginzburg and Cahn) for the kinetics of phase transitions

Chemical Physics, 1976

We postulate a master equation and derive by path integral methods the Cahn equation for the most... more We postulate a master equation and derive by path integral methods the Cahn equation for the most probable evolution of a nonuniform system. To do so we need to impose a constraint of local conservation of the variable of interest. The same derivation without this constraint has been shown previously to lead to a Landau-Ginzburg equation. Thus the two equations

Research paper thumbnail of On the path integral representation of stochastic processes

Journal of Statistical Physics, 1976

We derive the path integral representation of the conditional probability for a Markovian process... more We derive the path integral representation of the conditional probability for a Markovian process starting from the master equation. Existing derivations require both the variable and the transition probability to be extensive. We show that this requirement may be relaxed if Langer's formula for the transition probability is used. We prove that different path integral representations appearing in the literature are in fact equivalent and correspond to various choices of an arbitrary parameter.

Research paper thumbnail of Stochastic theory of the kinetics of phase transitions

Chemical Physics, 1976

We present a stochastic theory of the kinetics of phase transitions in univariant, nonuniform sys... more We present a stochastic theory of the kinetics of phase transitions in univariant, nonuniform systems. We assume a master equation and a relation of the transition probability to the free energy [J. S. Langer, Ann. Phys. (N.Y) 65, 53 (1971)]. The free energy is taken to be of the Cahn-Hilliard form. By means of path integral methods we obtain a

Research paper thumbnail of Coherent and diffusional motion of a chemisorbed atom

Chemical Physics Letters, 1976

Research paper thumbnail of Molecular dynamics simulations of nonequilibrium spatial correlations in a reaction diffusion system

Physica A-statistical Mechanics and Its Applications, 1994

In this paper we discuss the influence of nonequilibrium effects on the rate of a thermally activ... more In this paper we discuss the influence of nonequilibrium effects on the rate of a thermally activated, exothermic reaction. The system with a binary process A A B B + ⇔ + +{ } energy is considered as an example, on which we compare molecular dynamics simulations with a simple phenomenology based on the assumption that a nonequilibrium state can be characterized by many time dependent temperatures. A good agreement between results of both methods is observed. We have found that the rate constants are changed significantly by the nonequilibrium effects, which affects system's evolution.

Research paper thumbnail of The Possibility of Controlling Spin States of Surface Beam by Electromagnetic Waves on the Surface of Dielectrics

Electromagnetic waves in vacuum is transverse. However, the evanescent light can produce spatiall... more Electromagnetic waves in vacuum is transverse. However, the evanescent light can produce spatially alternative pattern of liearly polarized light and cir cularly polarized light.