Irreversibility in strongly coupled systems

A Boltzmann H-functional is derived in the so called physical representation introduced by Prigogine et al. It is proved that at equilibrium it contains the potential contributions to the specific entropy of the moderately dense gas. We shall discuss its validity in the linear domain of irreversible processes.     

Intermittency and dynamical chaos in reversible spontaneous emission

It is shown that a type of reversible spontaneous emission, the chaotic vacuum Rabi oscillations, may occur in the interaction of two-level atoms strongly coupled with a single cavity mode under a modulation of the atom-field coupling. Such a modulation arises naturally if the atoms move through a cavity in maserlike experiments. The existence of homoclinic chaos in reversible spontaneous emission is proven analytically. Evidence of intermittency associated with the spatial modulation of the vacuum Rabi frequency is shown numerically for the values of parameters that are achievable in present-day experiments with Rydberg atoms moving through a high-Q microwave cavity in the strong-coupling regime.     

Irreversibility of two-dimensional vortex systems with random pinning

We study irreversible flows in two-dimensional vortex systems with quenched random pins under periodical driving force using molecular dynamics simulation. Two irreversible flows are observed and the different mechanisms are investigated. Our results indicate that quenched random pins play important roles to cause irreversible flows.     

Lower-dimensional tori in reversible systems

On a (2n+d)-dimensional manifold M consider a vector field V reversible with respect to an involution G whose fixed point manifold is of dimension n+d. It is conjectured that generically for each 0相似文献   

Phase transition of superparamagnetic system in spontaneous coherent state

In the system of magnetic particles in superparamagnetic that interacted with resonance radiation field, phase transition in the spontaneous coherent state takes place. There are brought critical value for temperature and density of the system. Direct magnetic dipole-dipole interactions take into account in the molecular field approximation and it influence on the conditions of the phase transition is investigated.     

Multiphoton coherent control in complex systems

Control of multiphoton transitions is demonstrated for a multilevel system by generalizing the instantaneous phase of any chirped pulse as individual terms of a Taylor series expansion. In the case of a simple two-level system, all odd terms in the series lead to population inversion while the even terms lead to self-induced transparency. The results hold for multiphoton transitions that do not have any lower-order photon resonance or any intermediate virtual state dynamics within the laser pulse width.     

Bounded coherent states and excitonic systems

New bounded coherent state construction, based in a Keldysh conjecture, is presented. The particular group structure arising from the model leads a new symmetry transformations for the coherent state system. The emergent new symmetry transformations are reminiscent of the Bogoliubov ones. This construction is applied to describe an excitonic system. We discuss how the symmetry of these transformations is intrinsically related with the stability and the behavior of the physical systems as in the excitonic case.     

Coulomb drag in coherent mesoscopic systems

We present a theory for Coulomb drag between two mesoscopic systems. Our formalism expresses the drag in terms of scattering matrices and wave functions, and its range of validity covers both ballistic and disordered systems. The consequences can be worked out either by analytic means, such as the random matrix theory, or by numerical simulations. We show that Coulomb drag is sensitive to localized states, which usual transport measurements do not probe. For chaotic 2D systems we find a vanishing average drag, with a nonzero variance. Disordered 1D wires show a finite drag, with a large variance, giving rise to a possible sign change of the induced current.     

Irreversibility paradox revised: Onset of a center manifold in dissipative systems

A center-manifold-reduced Fokker-Planck equation is derived, starting from a time-reversible Liouville equation. The derivation is valid when there is a large separation of relaxation-time scales causing the phase-space contraction near a dynamic critical point. The paradox of breaking of time-reversal symmetry in the resulting Fokker-Planck equation at the onset of the center manifold is clarified.     

Self-amplification of coherent spontaneous emission in a cherenkov free-electron maser

Ultrashort pulses of microwave radiation have been produced in a dielectric-lined Cherenkov free-electron maser (FEM) amplifier. An intense initial seed pulse, due to coherent spontaneous emission (CSE), arises at the leading edge of the electron pulse. There is evidence to show that 3-4 cycle spikes are produced through the amplification of these seed pulses. A strong dependence of the start-up power on the rise time of the electron pulse has been found. The experimental results are verified by a theoretical analysis. Our study shows that amplification in a FEM amplifier is always initiated by CSE arising from the edge of the electron pulse when the rise time is comparable to the electromagnetic wave period.     

Effect of saturation in the field of coherent and intrinsic spontaneous radiation

Saturation effects in gaseous media in the presence of a high-intensity resonant laser field and in the field of incoherent radiation caused by the intrinsic spontaneous emission are considered. A simple nonlinear set of kinetic equations is proposed for describing the saturation effect in the case of optically thin media and nondegenerate levels. The Bennett structure and the band of homogeneous saturation, whose parameters are interdependent, exist in the velocity distribution. The regularities in the behavior of the band and the Bennett structure under variation in the transition parameters and the intensity of laser radiation are elucidated.     

Production of coherent states in biological systems

It is shown that Glauber-type coherent states exist in biological systems as a result of the broken symmetry of the free phonons. The symmetry of the system is reduced by the presence of the interaction terms in the hamiltonian. The coherent states so produced allow for the existence of giant dipoles capable of long-range interactions.     

Phase transition in spontaneous coherent state in Dicke model and retarded potentials

In contrast with the results by Rzazewski, Wodkiewicz and Zakowicz who have taken only the A²-term, it is shown that addition of the retarted potentials to the Dicke Hamiltonian conserves the threshold condition of a phase transition.     

Some comments on the use of phased angular momentum states in the theory of coherent spontaneous emission from large systems

We stress the importance of using phased atomic states when describing coherent spontaneous emission from large atomic systems. A sufficient criterion for the existence of a preferred direction of emission is deduced from dynamical arguments.     

Quantum coherent effects in multi-Zeeman-sublevel atomic systems

This paper reports the experimental results on electromagnetically induced absorption （EIA） spectra observed in the system which does not satisfy completely the conditions given by Lezama et al [1999 Phys. Rev. A 59 4732]. EIA signals on the transitions in the Cs D2 line are able to be observed, where Fg ←→ Fe = Fg-1 as open systems. Theoretical model of Lezama et al is good for the case Fg ←→ Fc = Fg ＋ 1, considering spontaneous transfer of atomic coherences or populations this model is not able to explain our experimental results obtained in the case Fg ←→ Fe = Fg - 1. This paper offers a theoretical model which is able to well explain the case Fg ←→ Fc = Fg - 1. It also uses this theoretical model to explain the split and shift of EIA peaks, which have been obtained in experiments.