On the conventional QED interpretation of the GSI ee narrow resonances

A possible mechanism for the GSI e⁺e^- narrow resonances as being due to non-perturbative effects of conventional QED is proposed. An application of the quasi-potential approach discloses a set of new resonances in a system of two charged particles. Numerical calculations agree with data on e⁺e^- and pp narrow resonances. Additional new resonances are predicted for e⁺e^-, pp, e^-e^- systems.     

Accurate transport cross sections for the Lennard-Jones potential

It is well-known that in open quantum systems resonances can coalesce at an exceptional point, where both the energies and the wave functions coincide. In contrast to the usual behaviour of the scattering amplitude at one resonance, the coalescence of two resonances invokes a pole of second order in the Green’s function, in addition to the usual first order pole. We show that the interference due to the two pole terms of different order gives rise to patterns in the scattering cross section which closely resemble Fano-Feshbach resonances. We demonstrate this by extending previous work on the analogy of Fano-Feshbach resonances to classical resonances in a system of two driven coupled damped harmonic oscillators.     

Application of the diffraction trace formula to the three-disk scattering system

The diffraction trace formula derived previously and the spectral determinant are tested on the open three-disk scattering system. The system contains a generic and exponentially growing number of diffraction periodic orbits. In spite of this it is shown that even the scattering resonances with large imaginary part can be reproduced semiclassically. The nontrivial interplay of the diffraction periodic orbits with the usual geometrical orbits produces the fine structure of the complicated spectrum of scattering resonances, which are beyond the resolution of the conventional periodic orbit theory.     

Controlling the optical bistability via interacting dark-state resonances

We analyze the behavior of optical bistability in a four-level mercury atomic system driven by a cavity and two external coherent fields by means of a unidirectional ring cavity. We find that without interacting dark resonances and for large intensity of coupling field, the optical bistability disappears. So, the double dark resonances could significantly establish the optical bistability. Moreover, we demonstrate that the double dark resonances can dramatically reduce the threshold of optical bistability.     

Resonances in Scattering. I. Basic Equations and Main Approximations

We describe the main features of resonances in scattering, determining the resonances in view of the theory of collisions in a two-body system, as well as the resonances emerging as a result of collisions in a few-body system. We analyze regularities in the emergence of such resonances and their characteristics. We discuss the results of calculations of the resonant processes occurring during collisions of electrons with diatomic molecules, in view of the quantum theory of scattering in a few-body system based on the Faddeev–Yakubovsky equations.     

The effect of experimental geometry and initial conditions on the shape of coherent population trapping resonances on the fine structure levels of thallium atoms

Specific features of the coherent population trapping effect are considered in the generalized Λ system whose lower levels are the magnetic sublevels of the fine structure levels of the thallium atom. Numerical experiments were performed aimed at examination of the coherent population trapping for the case of nontrivial, but feasible, initial populations of the upper metastable fine structure level. Such populations may be obtained, for example, due to the photodissociation of TlBr molecules. The possibility of reducing the number of resonances of the coherent population trapping in a multilevel system, which may be useful for high-resolution spectroscopy, is demonstrated. It is shown that the magnitude and shape of the resonances can be controlled by varying the orientation of the polarization vectors of the light field components with respect to each other and to a magnetic field. In addition, studying the shape of the coherent population trapping resonances for the atoms obtained by photodissociation of molecules may provide information about these molecules.     

Optical size resonances in nanostructures

The existence of optical size resonances in atomic nanostructures is proved. The properties of optical size resonances strongly depend on the interatomic distances and on the polarization of an external radiation field. The properties of linear and nonlinear size resonances are considered in the case of two-dimensional nanostructures. The linear optical size resonances are described based on a closed system of equations for dipole oscillators and nonlocal field equations taking into account the dipole-dipole interactions of atoms in the radiation field. Using a stationary solution to these equations, it is demonstrated that two isotropic atoms with definite intrinsic frequencies form an anisotropic system in the radiation field, possessing two or four size resonances depending on whether the component atoms are identical or different. The nanostructure composed of two different atoms possesses two size resonances with positive dispersion and two other resonances with negative dispersion. The frequencies of the size resonances significantly differ from the intrinsic frequencies of isolated atoms entering into the nanostructure. By changing the angle of incidence of the external wave, it is possible to excite various size resonances. The properties of nonlinear optical size resonances excited by an intense radiation field were theoretically and numerically studied using the modified Bloch equations and nonlocal field equations. Dispersion relationships for the nonlinear resonances were derived and the inversion properties of atoms in the nanostructure were studied for various polarizations of the external optical wave.     

An Analytic Model of the Minimum-Average-B Levitron

An expansion model to the first order in r, which includes the toroidal correction, and which is feasible for analytical calculations, is derived in the curvilinear toroidal system of coordinates for the minimum-average-B levitron. Expansions, in powers of r, are derived for the current ring potential, the magnetic field components of the axisymmetric levitron, and the components of the perturbation of the magnetic field of the nonaxisymmetric levitron. Published analytical works treated the straight levitron's approximation which contains only the ? and 2? resonances of the system. The advantage of this model is that it contains all the numerically observed resonances of the levitron.     

Nonlinear resonances in the absorption spectrum of the three-level atomic V system in strong polyharmonic and weak biharmonic fields

A three-level atomic system with a strong three-mode field and a probing biharmonic field at transitions 1→2 and 1?3 (1 is a common lower level), respectively, is studied theoretically by numerical simulation and an analysis of the mathematical expressions derived for the particular case of a symmetric arrangement of the strong field components relative to the transition frequency ω₂₁. The absorption spectrum of the probing field components contains parametric supernarrow resonances against the background of resonances of the nonlinear interference effect. The ratios of the differences in the frequencies of the strong and probing fields, at which the supernarrow resonances appear, are found analytically. The results coincide with those obtained from numerical simulation.     

Effect of Resonant Photon Emission in Radiative Heat Transfer and Generation

The effect of resonances in the photon emission rate in the radiative heat generation and transfer and the Casimir friction at the sliding of two polar dielectric plates has been studied. The resonances have different origin in the frequency ranges of the normal and anomalous Doppler effects. In the frequency range of the normal Doppler effect, the resonances are due to resonant photon tunneling between surface phonon/plas-mon polaritons of plates. Such resonances exist only at a relative sliding velocity v = 0 for two identical plates. However, the resonances may occur at v ≠ 0 for different plates. In the frequency range of the anomalous Doppler effect, the resonances are due to the excitation generation in both plates. While the resonances are finite in the frequency range of the normal Doppler effect, singular resonances are possible even in the presence of dissipation in the system in the frequency range of the anomalous Doppler effect. The resonances for identical and different sliding plates have been considered.

     

Recent developments in the theory of stripping to unbound states

A comparative analysis is carried out of different approaches to the calculation of DWBA cross sections for stripping to unbound states including single-particle resonances, compound resonances and the smooth background. A relationship is derived between unbound stripping and scattering cross sections on the same target. The reliability of spectroscopic factor concepts is discussed. Numerical checks are performed with the aid of stripping form factors obtained from the solution of a coupled channels equation system.     

Possibility of new resonances in transient nonlinear spectroscopy

We predict the existence of new types of extra resonances in transient four wave mixing from a system with negligible collisions. These new resonances arise from the coherent pumping and disappear in the long time limit. We give explicit results for extra resonances in four wave mixing from several conventonally used systems.     

On the formation of structure and electronic transport

By systematic studies of amorphous systems (and most of the results are transferable to liquid systems) we are able to show that structure formation at early stages is to a high degree the effect of self-organized and hence optimized resonances between macroscopic subsystems. There is, for example, a spherical-periodic resonance, based on momentum exchange between the valence electrons in total as one subsystem, and the forming static structure as the other one. It causes spherical structural periodicity of nearest-neighbour shells at medium distances and is a global effect, giving rise to similar effects as described by Bloch's theorem in crystals. Resonances based on an exchange of angular momentum became apparent too. Accordingly, together with the local quantum chemical effects, global resonances are important as well and both will cooperate to get the most optimal energetic situation for the total system. Occasionally, the global effects even dominate structure formation. We report on different scenarios where the total system is able to optimize the resonances. The resonance model explains major structural features of many liquid and amorphous systems of different types as there are pure elements, binary as well as ternary alloys, metallic glasses, glassy semiconductors, glassy Zintl systems, and light-weight Al–TM alloys (TM: from Ti to Cu). Spherical-periodic order causes pseudogaps or even gaps at the Fermi energy and hence has dramatic influences on any electronic transport. Accordingly, understanding structure formation on the basis of resonances also triggers a deeper understanding of electronic transport properties.     

Three-boson problem near a narrow Feshbach resonance

We consider a three-boson system with resonant binary interactions and show that for sufficiently narrow resonances three-body observables depend only on the resonance width and the scattering length. The effect of narrow resonances is qualitatively different from that of wide resonances revealing novel physics of three-body collisions. We calculate the rate of three-body recombination to a weakly bound level and the atom-dimer scattering length and discuss implications for experiments on Bose-Einstein condensates and atom-molecule mixtures near Feshbach resonances.     

Linear and nonlinear resonance features of an erbium-doped fibre ring laser under cavity-loss modulation

The continuous-wave output of a single-mode erbium-doped fibre ring laser when subjected to cavity-loss modulation is found to exhibit linear as well as nonlinear resonances. At sufficiently low driving amplitude, the system resembles a linear damped oscillator. At higher amplitudes, the dynamical study of these resonances shows that the behaviour of the system exhibits features of a nonlinear damped oscillator under harmonic modulation. These nonlinear dynamical features, including harmonic and subharmonic resonances, have been studied experimentally and analysed with the help of a simple time-domain and frequency-domain information obtained from the output of the laser. All the studies are restricted to the modulation frequency lying in a regime near the relaxation oscillation frequency.     

The effects of floating slab bending resonances on the vibration isolation of rail viaduct

This paper compared the performance of several isolation designs to control vibration transmissions from concrete rail viaducts. The isolation systems analysed includes medium- and short-length floating slabs, and floating ladders. The vibration was measured in Japan, Korea and Hong Kong. The study aimed to assess the effects of bending resonances of the floating slab systems. Simple formulae of estimating the significant bending resonance frequency and support passage frequency of a floating slab system are proposed. The resonance peaks obtained in site measurement are found to be in agreement with the calculation results. The results show that other than the vertical rigid body resonances for the isolation systems, the bending resonances of slabs have significant effects on vibration isolation performance. In particular, bending resonance frequencies should not coincide with the vertical isolator resonance and support passage frequency. According to the in-situ measurement results, a mini-type concrete floating slab can reduce the vibration level by more than 30 dB in the frequency range of 63-200 Hz. This should be achieved by designing the first bending resonances of the floating slab to be out of the dominant frequency range of concrete rail viaduct vibration.     

Streaminglike diffusion in the low-dimensional stochastic pump model

In this paper we analyze a diffusion phenomenon in a few-dimensional Hamiltonian system of coupled mappings in which the principal component of diffusion occurs along resonances. The result is that the diffusion can have power-law dependence in coupling parameter mu and be independent of the stochastic parameter K. For the same range of parameters, the usual analytical Arnold diffusion across resonances is dependent on K and can be much smaller than resonance streaming diffusion. The results are used to qualitatively explain recent results in multidimensional coupled standard maps.     

Collapse of resonances in semiconductor heterostructures as a transition with symmetry breaking in an open quantum system

The collapse of resonances in resonant tunneling heterostructures, which is merging of two unit-transparency resonances into a single resonance with transparency less than unity has been theoretically analyzed. The electron density distribution becomes asymmetric at the collapse point in a geometrically symmetric system. The asymmetry parameter behaves as the order parameter in the second-order phase transition. The physical mechanism of the transition is associated with the broadening of the quasistationary levels of a quantum system due to the interaction with the continuum of delocalized states. The possibility of the existence of two qualitatively different types of low-energy resonances differing in the sign of the effective range of the potential has been demonstrated.