Rotation of laser beams with zero of the orbital angular momentum

We show that among the multitude of rotating light beams whose complex amplitude can be represented as a linear superposition of the Laguerre-Gaussian (LG) modes with definite numbers there are light beams with zero orbital angular momentum (OAM) and vice versa, multi-mode LG beams that show no rotation and are lacking the radially symmetric intensity distribution can possess the non-zero OAM. Also, we give examples of the rotating light beams with zero OAM, represented as a superposition of the Bessel and new hypergeometric modes. Using an SLM, we generate a rotating Bessel beam with zero OAM for the first time.     

Barrier-wave-internal-wave interference and airy minima in 16O16+O elastic scattering

Taking 16O+16O elastic scattering at 124 MeV as an example, we show that a barrier-wave-internal-wave decomposition of the elastic scattering amplitude provides valuable information on the light heavy-ion interaction and complements the more conventional nearside-farside decomposition. In particular, we show that the Airy minima present in the angular distributions are due to a barrier-wave-internal-wave interference mechanism, which sheds additional light on the exceptional transparency displayed by some light heavy-ion scattering systems. Extension of these ideas to other fields, like atomic and molecular collision physics, could prove rewarding.     

Test of the heavy quark–light diquark approximation for baryons with a heavy quark

We check a commonly used approximation in which a baryon with a heavy quark is described as a heavy quark–light diquark system. The heavy quark influences the diquark internal motion reducing the average distance between the two light quarks. Besides, we show how the average distance between the heavy quark and any of the light quarks, and that between the heavy quark and the center of mass of the light diquark, are smaller than the distance between the two light quarks, which seems to contradict the heavy quark–light diquark picture. This latter result is in agreement with expectations from QCD sum rules and lattice QCD calculations. Our results also show that the diquark approximations produces larger masses than the ones obtained in a full calculation.     

Ghost imaging with white light speckle patterns

In this paper we describe a method to study the formation of a ghost image by using a simplified setup. A spatial light modulator (SLM) working in amplitude regime is used both to display the object and the intensity distribution that provides the high-spatially correlated beams which are the base of this phenomenon. We compare the recovered ghost image with that obtained by using pseudothermal light. Moreover we show that good quality images are also retrieved when a turbulent media is present.     

SU(1,1)相干态光场的统计特性及其对原子动力学行为的影响

研究了Ｂａｒｇｍａｎ指标为ｋ＝１／４和ｋ＝３／４的两种ＳＵ（１，１）相干态光场的特性，证明了两种相干态具有不同的量子统计特性，并讨论了光场初始处于ＳＵ（１，１）相干态时，双光子Ｊａｙｎｅｓ－Ｃｕｍｍｉｎｇｓ（Ｊ－Ｃ）模型中，原子的动力学行为及粒子数反转随时间的演化，证明了与初始一般相干态光场不同，原子展现出特殊的周期振荡和脉冲行为。 关键词：     

Optical pumping in a L-system by parametric luminescence light

We examine the optical pumping effect in an ensemble of three-level atoms with a Λ configuration of the energy sublevels excited by parametric luminescence light in the squeezed state. We derive quantum kinetic equations that describe the evolution of the density matrix of atoms irradiated by low-intensity squeezed light with a finite-width spectrum. In particular, we show that because of the quantum statistical properties of the squeezed light there can be a redistribution of atoms among the lower energy sublevels, despite the equality of the intensities of the spectral components of the light that resonantly excites optical transitions in the Λ-system. The relation of the optical pumping effect to the correlation and spatial-temporal spectral properties of squeezed light is discussed in detail. Finally, we show that the effects are closely linked to the finiteness of the width of the squeezed-light spectrum. Zh. éksp. Teor. Fiz. 112, 137–162 (July 1997)     

The coordinate transformations of the absolute space-time theory

In the light of our recently performed experiments, revealing the anisotropy of light velocity in any frame moving with respect to absolute space, we show that the Lorentz transformation, where the relativity of light velocity is given implicitly through the relativity of the time coordinates, must be treated from an absolute point of view if one seeks to preserve its adequacy to physical reality. Then we propose a new transformation (which is to be considered as a legitimate companion of the Lorentz transformation) wherein the relativity of light velocity is given explicitly and the time coordinates are absolute.     

General neutrino mass spectrum and mixing properties in seesaw mechanisms

Neutrinos stand out among the elementary particles because of their unusually small masses.Various seesaw mechanisms attempt to explain this fact.In this work,applying insights from matrix theory,we are in a position to treat variants of seesaw mechanisms in a general manner.Specifically,using Weyl's inequalities,we discuss and rigorously prove under which conditions the seesaw framework leads to a mass spectrum with exactly three light neutrinos.We find an estimate of the mass of heavy neutrinos to be the mass obtained by neglecting light neutrinos,shifted at most by the maximal strength of the coupling to the light neutrino sector.We provide analytical conditions allowing one to prescribe that precisely two out of five neutrinos are heavy.For higher-dimensional cases the inverse eigenvalue methods are used.In particular,for the CP-invariant scenarios we show that if the neutrino sector has a valid mass matrix after neglecting the light ones,i.e.if the respective mass submatrix is positive definite,then large masses are provided by matrices with large elements accumulated on the diagonal.Finally,the Davis-Kahan theorem is used to show how masses affect the rotation of light neutrino eigenvectors from the standard Euclidean basis.This general observation concerning neutrino mixing,together with results on the mass spectrum properties,opens directions for further neutrino physics studies using matrix analysis.     

Propagation of Light in an Ensemble of Tripod Level Atoms

We study the propagation of a quantum probe light in an ensemble of tripod level atoms when the atoms are coupled to two other classical control fields. First we calculate the dispersion properties, such as susceptibility and group velocity, of the probe light within such an atomic medium under the case of three-photon resonance via the dynamical algebra method of collective atomic excitations. Then we calculate the dispersion of the probe light in the case that two classical control fields have the different detunings to the relative atomic transitions. Our results show that in both cases the phenomenon of electromagnetically induced transparency can occur. Especially under the second case, we can find two transparency windows for the probe light.     

Propagation of Light in an Ensemble of Tripod Level Atoms

We study the propagation of a quantum probe light in an ensemble of tripod level atoms when the atoms are coupled to two other classical control fields. First we calculate the dispersion properties, such as susceptibility and group velocity, of the probe light within such an atomic medium under the case of three-photon resonance via the dynamical algebra method of collective atomic excitations. Then we calculate the dispersion of the probe light in the case that two classical control fieMs have the different detunings to the relative atomic transitions. Our results show that in both cases the phenomenon of electromagnetically induced transparency can occur. Especially under the second case, we can find two transparency windows for the probe light.     

Sagnac Effect of Gödel's Universe

We present exact expressions for the Sagnac effect of Gödel's Universe. For this purpose we first derive a formula for the Sagnac time delay along a circular path in the presence of an arbitrary stationary metric in cylindrical coordinates. We then apply this result to Gödel's metric for two different experimental situations: First, the light source and the detector are at rest relative to the matter generating the gravitational field. In this case we find an expression that is formally equivalent to the familiar nonrelativistic Sagnac time delay. Second, the light source and the detector are rotating relative to the matter. Here we show that for a special rotation rate of the detector the Sagnac time delay vanishes. Finally we propose a formulation of the Sagnac time delay in terms of invariant physical quantities. We show that this result is very close to the analogous formula of the Sagnac time delay of a rotating coordinate system in Minkowski spacetime.     

Observation of carrier-envelope phase phenomena in the multi-optical-cycle regime

So far the role of the carrier-envelope phase of a light pulse has been clearly experimentally evidenced only in the sub-6-fs temporal regime. Here we show, both experimentally and theoretically, the influence of the carrier-envelope phase of a multi-optical-cycle light pulse on high-order harmonic generation. For the first time, we demonstrate that the short and long electron quantum paths contributing to harmonic generation are influenced in a different way by the pulse carrier-envelope phase.     

Nature of light scalars through photon-photon collisions

The surprising thing is that arising almost 50 years ago from the linear sigma model(LSM)with spontaneously broken chiral symmetry,the light scalar meson problem has become central in the nonperturbative quantum chromodynamics(QCD)for it has been made clear that LSM could be the low energy realization of QCD.First we review briefly signs of four-quark nature of light scalars.Then we show that the light scalars are produced in the two photon collisions via four-quark transitions in contrast to the classic P wave tensor q(q)mesons that are produced via two-quark transitions γγ→q(q).Thus we get new evidence of the four-quark nature of these states.     

Period-doubling bifurcations from breaking the spherical symmetry in sonoluminescence: experimental verification

Using a fiber-based four-channel correlation scheme to investigate spatial and temporal correlations, we show that observations of period-doubling phenomena in single bubble sonoluminescence are primarily a result of spontaneously breaking the spherical symmetry in the bubble collapse and, at most, may show up as secondary effects in the flash-to-flash spatially integrated light output.     

Mie scattering and the physical mechanisms of sonoluminescence

We propose an experimental procedure to investigate possible mechanisms for radiation emission in sonoluminescence. Our analysis is based on Mie's theory of light scattering for a coated sphere in an external medium. Depending on the physical mechanism responsible of sonoluminescence, the dielectric constant of the hot spot changes. As a case study we consider the problem of the detection of an inner plasma core in sonoluminescent bubbles. Our results show that polarization measurements of scattered light should discern the presence of a plasma provided that light detectors are fast enough. Extensions to other emission mechanisms are briefly discussed.     

信号灯和公交车站对T形路口交通流的影响研究

采用非线性映射模型研究T形路口的交通问题,利用点平均流量指标系统地分析了公交车站、信号灯周期、绿信比、车辆左右转弯等因素对路径交通流量的影响.数值模拟结果表明,信号灯和公交车站之间的相互影响容易导致交通流的串现象,不同路径上的流量与信号灯周期、绿信比和公交车站位置之间存在一定的关系. 关键词： 交通流 非线性映射模型 信号控制 串     

Amplified extended modes in random lasers

We report on a new random laser phenomenon that gives rise to narrow emission modes without requiring optical cavities. Sharp emission peaks are observed experimentally over a broad range of scattering strengths and analyzed in numerical calculations. We find that the introduction of exponential gain in a multiple light scattering process strongly increases the importance of very long light paths. Such long paths are rare and often neglected in passive disordered materials but we show that they can dominate the emission spectrum from an amplifying disordered system.     

Enhanced squeezing and entanglement in a non-degenerate three-level cascade laser with injected squeezed light

We consider a non-degenerate three-level cascade laser coupled to a two-mode squeezed vacuum reservoir via the lossy single-port mirror. Applying the pertinent master equation, we analyze the effects of the injected squeezed light on the quadrature squeezing, entanglement and normalized intensity difference fluctuations. We show that the injected squeezed light considerably enhances the degree of squeezing and entanglement in the two-mode light for certain initial conditions. Moreover, the injected squeezed light increases the mean photon number where the squeezing and entanglement is significant. We also show that the presence of the injected squeezed light greatly reduces the noise in the intensity difference.     

Particle Characterization Using Multiple Scattering Decorrelation Methods. Part 1: Standard Latex Particles

We determined the dimensions of standard polystyrene latex spheres suspended in water at different sample concentrations by dynamic light scattering and turbidimetry. Applying two different schemes for the decorrelation of multiple scattering, we show that the samples exhibit distortions of the auto-correlation function due to multiple scattering even at moderate volume fractions, which prohibits the correct determination of the particle radius. The cross-correlation functions, however, are free from these distortions. The recently deployed three-dimensional cross-correlation setup is superior to the commercially available two-color machine, as more turbid samples are accessible. In order to verify the results obtained by dynamic light scattering, we performed turbidity measurements with the same samples. This method is inherently free from multiple scattering contributions. We observe a systematically smaller radius in turbidimetry than in dynamic light scattering. The deviation, however, is only slightly outside the accuracy range of the measurements. We discuss possible origins for this deviation and show that our measurements are compatible with a hairy layer present on the particle's surface.