General formula for phonon-assisted n-photon absorption in solids

A general formula for phonon-assisted n-photon absorption in solids is obtained by (n+1)-th order perturbation technique. The complicated calculation process for transition element of n-photon absorption is simply demonstrated by a diagram approach that is proposed in this work. We find that the transition element for the n-photon absorption has a simple form, i.e., it is just the first term of the n-th order fist kind Bessel function.     

一种新型的多模虚偶相干态光场的等阶N次方Y压缩与等阶N次方H压缩

本文利用新近建立的多模压缩态理论,详细研究了一种新型的多模虚偶相干态光场|Ψ_i,e⁽²⁾>_q的广义非线性等阶N次方Y压缩与等阶N次方H压缩特性.结果发现:1)态|Ψ_i,e⁽²⁾>_q是一种典型的多模非经典光场,当压缩阶数N为奇数时,态|Ψ_i,e⁽²⁾>_q在一定条件下总可呈现出周期性变化的、任意阶的等阶N次方Y压缩效应;当腔模总数q与压缩阶数N这两者的乘积q·N为奇数时,则在一定条件下态|Ψ_i,e⁽²⁾>_q又可呈现出周期性变化的、任意阶的等阶N次方H压缩效应.2)态|Ψ_i,e⁽²⁾>_q的等阶N次方Y压缩与等阶N次方H压缩效应这两者的压缩程度和压缩深度分别与几率幅γ_q^(e)、压缩参数R_j、各模的初始相位φ_j(或者各模的初始相位和 φ_j)、压缩阶数N以及腔模(指纵模)总数q等呈较强的非线性关联,等阶N次方H压缩效应与上述诸参量之间的非线性关联程度要比等阶N次方Y压缩效应的更强.3)多模虚偶相干态光场|Ψ_i,e⁽²⁾>_q与多模偶相干态光场|Ψ_,e>_q及多模复共轭偶相干态光场|Ψ*_,e⁽²⁾>_q这后两者的等阶N次方Y压缩效应和等阶N次方H压缩效应的压缩条件和压缩特性正好相反,这种现象就称为相反压缩.     

多模复共轭奇、偶相干态光场的N次方Y压缩与N次方H压缩

利用新近提出的多模辐射场的广义非线性等阶高阶压缩理论,对多模复共轭奇、偶相干态光场的N次方Y压缩与N次方H压缩特性进行了详细研究.结果发现:①多模复共轭奇相干态光场,压缩阶数N为偶数时,只存在N-Y最小测不准态;而当腔模总数q与压缩阶数的乘积q·N为偶数时,只存在N-H最小测不准态;此外,无论N及q·N为何值,不呈现N次方Y压缩与N次方H压缩效应.②多模复共轭偶相干态光场在一定条件下可呈现出周期性变化的任意阶的N次方Y压缩与N次方H压缩效应.③多模偶相干态光场与多模复共轭偶相干态光场两者的压缩效果和压缩特性完全相同,这种现象称为“压缩简并”.     

Electron spin resonance and antiferromagnetic resonance of single crystals of yttrium doped with gadolinium

The nonlinear interaction of oscillation modes is investigated on the basis of Lagrangian formalism. Equations describing the changes of the bound mode amplitudes versus time, are obtained. It is shown that the energy transformation between different modes is of a periodic nature: if in the initial moment of time an appreciable part of the energy is contained, for example, in them-th mode, then after a period of timeTt (called a time of nonlinear interaction) the energy will be transformed to then-th mode. Expressions forT _t for cases with the interaction of two and three modes are obtained. As a particular case the process of nonlinear interaction of the electron “transverse” and “longitudinal” oscillations in the highfrequency hybrid resonance region of a “weakly” inhomogeneous plasma was investigated.     

第Ⅰ类两态叠加多模叠加态光场的非线性高阶压缩特性研究

本文在文献20的基础上进一步提出了多模辐射场的N-Y最小测不准态、N-H最小测不准态、N-Y压缩最小测不准态以及N-H压缩最小测不准态等的定义.构造了由多模(q模)相干态|{Z_j}>_q及其相反态|{-Z_j}>_q的线性叠加所组成的第Ⅰ类两态叠加多模叠加态光场|ψ₁⁽²⁾>_q,利用文献20新近提出的有关多模辐射场的两种非线性高阶压缩的定义,首次对态|ψ₁⁽²⁾>_q的N次方Y压缩及N次方H压缩效应进行了详细研究.结果表明,1)当N为偶数时,态|ψ₁⁽²⁾>_q恒处于N-Y最小测不准态;当N为奇数时,态|ψ₁⁽²⁾>_q在一定条件下可呈现出周期性变化的、任意阶的N次方Y压缩效应.2)当q·N为偶数时,态|ψ₁⁽²⁾>_q恒处于N-H最小测不准态;当q·N为奇数时,在另外的条件下,态|ψ₁⁽²⁾>_q则可呈现出周期性变化的、任意阶的N次方H压缩效应.3)N次方Y压缩及N次方H压缩效应的压缩深度与腔模总数q、压缩参数R_j以及压缩阶数N等非线性相关,后者与上述参量的非线性关联程度要比前者的更强.     

On the waves and instability in self-gravitating magnetic molecular clouds with ambipolar diffusion Part 1: Planar modal approach

It is well established that molecular clouds are the main sites of active star formation in our Galaxy. The interaction of the three major physical agents in molecular clouds, i.e. the self-gravity, magnetic fields, and ambipolar diffusion, in the form of waves and instability, governs the dynamics and evolution of molecular clouds. The present work is a new effort on this subject. This work consists of two parts. In Part 1, we complete the planar modal analysis by removing the restrictions on the direction of the velocity perturbation which were used in previous studies. Thus, the wave number vector k is allowed to take any direction with respect to the mean field B₀. The exact general dispersion relation is found to be a seventh-order equation and can be reduced to a quartic equation as the first approximation about the small parameter x_ρ = ρ_{i, 0}/ρ_n,0, the density ratio between ions and neutrals. The growth rate contour maps in the k plane are obtained for various values of the basic dimensionless parameters Λ and σ, where Λ = V_A,n/C_n is the ratio between the Alfvén speed and the sound speed in the neutrals, and the “coupling factor” σ = v_i/ω_g,n is the ratio between the average collision frequency of a neutral with ions and the self-gravitation response frequency. It is shown that, in all directions, magnetic field only reduces the growth rate but does not change the critical wave length for instability. The reduction of the growth rate depends on not only Λ, the dimensionless measure of the field strength, but also the direction of k as well as the coupling factor σ. The frequencies and the dissipation rates of the Alfvén waves and the fast and slow self-gravitating magnetosonic waves are calculated for all directions of k. The solutions of these waves are also given. Although the planar modal approach is important in understanding the basic mechanism of magnetic waves and instability, it does not take into account the three-dimensionality and the finite size of the cloud and is therefore only suitable to the local analysis. Thus, in order to discuss the global properties, we will develop a cylindrical modal approach in Part 2. There, we will also discuss certain nonlinear effects and show their importance in leading to a self-adjusting mechanism which slows down the global collapse at the early stage of cloud evolution and refreshes the outward propagating Alfvén and fast magnetosonic waves caused by star-forming or core-forming activities. In this way, a significant portion of the released gravitational energy during the global collapse is turned into the magnetic waves to support the cloud against the global collapse itself.     

Partial coherence in the core–halo picture of Bose–Einstein n-particle correlations

We study the influence of a possible coherent component in the boson source on the two-, three- and n-particle correlation functions in a generalized core–halo-type boson-emitting source. In particular, a simple formula is presented for the strength of the n-particle correlation functions for such systems. Graph rules are obtained to evaluate the correlation functions of arbitrarily high order. The importance of an experimental determination of the 4-th and 5-th order Bose–Einstein correlation function is emphasized. Received: 18 December 1998 / Published online: 20 May 1999     

Mode-Coupling and Nonlinear Landau Damping Effects in Auroral Farley-Buneman Turbulence

Abstract

The fundamental problem of Farley-Buneman turbulence in the auroral E-region has been discussed and debated extensively in the past two decades. In the present paper we intend to clarify the different steps that the auroral E-region plasma has to undergo before reaching a steady state. The mode-coupling calculation, for Farley-Buneman turbulence, is developed in order to place it in perspective and to estimate its magnitude relative to the anomalous effects which arise through the nonlinear wave-particle interaction. This nonlinear effect, known as nonlinear “Landau damping” is due to the coupling of waves which produces other waves which in turn lose energy to the bulk of the particles by Landau damping. This leads to a decay of the wave energy and consequently a heating of the plasma. An equation governing the evolution of the field spectrum is derived and a physical interpration for each of its terms is provided.     

态|Ψ(3)〉q中广义磁场的不等幂次高次振幅压缩

利用多模压缩态理论,研究了一种新型的三态叠加多模叠加态光场|Ψ⁽³⁾〉_q中广义磁场分量(即第一正交相位分量)的不等幂次高次振幅压缩特性.结果表明:态|Ψ⁽³⁾〉_q是一种典型的三态叠加多模非经典光场,其广义磁场分量在一定条件下可呈现出周期性变化的、偶数次的不等幂次高次振幅压缩效应.     

Control of higher order antibunching

Based on general physical arguments we derive a new general criterion for higher order antibunching. We show that the degree of antibunching increases with the order of antibunched photon states. We use the criterion for the case of the interaction of an intense electromagnetic field with a (k-1)-th order nonlinear medium. For a third order nonlinear and nonabsorbing medium with inversion symmetry, we show that the degree of antibunching can be tuned by changing the phase of the external field. PACS 42.50.Ar; 42.50.ct; 42.50.Dv     

Nonlinear reaction-diffusion: a microscopic approach

A microscopic theory for reaction-difusion (R-D) processes is developed from Einstein’s master equation including a reactive term. The mean field formulation leads to a generalized R-D equation for the n-th order annihilation reaction A + A + A + ... + A → 0, and the steady state solutions exhibit long range power law behavior showing the relative dominance of sub-diffusion over reaction effects in constrained systems, or conversely short range concentration distribution with finite support describing situations where diffusion is slow and extinction is fast. We apply the theory to analyze experimental data for morphogen gradient formation in the wing disc of the Drosophila embryo.     

多模复共轭虚偶相干态光场的等阶N次方Y压缩与等阶N次方H压缩

本文利用新近建立的多模压缩态理论,详细研究了一种新型的多模复共轭虚偶相干态光场|Ψ_i,e^*(2)>_q的广义非线性等阶N次方Y压缩与等阶N次方H压缩特性.结果发现:1)当压缩阶数N为奇数时,态Ψ_i,e^*(2)>_q在一定条件下总可呈现出周期性变化的、任意阶的等阶N次方Y压缩效应;当腔模总数q与压缩阶数N两者之乘积q·N为奇数时,则在一定条件下态|Ψ_i,e^*(2)>_q又可呈现出周期性变化的、任意阶的等阶N次方H压缩效应.2)态|Ψ_i,e^*(2)>_q与多模偶相干态光场|Ψ_i,e^*(2)>_q与多模虚偶相干态光场|Ψ_i,e⁽²⁾>_q的压缩幅度、压缩条件和压缩特征等完全相同.这一结果再次从理论上证实了多模压缩光中的确存在着“相反压缩”和“压缩简并”这两类新的物理现象.     

多模奇相干态光场中的N-Y最小测不准态与N-H最小测不准态

本文根据新近建立的多模辐射场的广义非线性等阶高阶压缩理论,对多模奇相干态光场|Ψ,o〉_q中的N次方Y压缩、N次方H压缩、N-Y最小测不准态以及N-H最小测不准态等进行了详细研究.结果表明:1)当压缩阶数N为偶数时,多模奇相干态|Ψ,o〉_q总是恒处于N-Y最小测不准态;当N为奇数时,态|Ψ,o〉_q既不处于N-Y最小测不准态,也不呈现N次方Y压缩效应.2)当q & #183;N为偶数时,多模奇相干态|Ψ,o〉_q总是恒处于N-H最小测不准态;当q & #183;N为奇数时,态|Ψ,o〉_q既不处于N-H最小测不准态,也不呈现N次方H压缩效应.3)多模奇相干态|Ψ,o〉_q恒处于N-Y最小测不准态与恒处于N-H最小测不准态的条件明显不同,两者存在着严格的区别.     

Directivity pattern of parametrically generated acoustic waves

Summary The generation of down-converted frequency waves in the nonlinear propagation of acoustic waves is examined, in order to investigate the effects produced by the finiteness of the medium or of the media of interaction. Oscillations of the directivity patternsvs. the width of the media of interaction are set in evidence and related to resonance conditions of the medium cavity. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

第V类两态叠加多模叠加态光场的广义非线性等阶N次方Y压缩

本文构造了由多模真空态|{0_j}>_q和多模虚相干态的相反态|{-iZ_j}>_q这两者的线性叠加所组成的第V类两态叠加多模叠加态光场|ψ₅⁽²⁾>_q.利用多模压缩态理论,研究了态|ψ₅⁽²⁾>_q的广义非线性等阶N次方Y压缩特性.结果发现:1)态|ψ₅⁽²⁾>_q是一种典型的多模非经典光场;无论压缩阶数N取奇还是取偶,只要各模的初始相位φ_j(j=1,2,3,…,…,q)和态间的初始相位差(θ_nq^(I)-θ_oq^(o))等满足一定的取值条件,态|ψ₅⁽²⁾>_q总可呈现出周期性变化的、任意奇数阶和任意偶数阶的广义非线性等阶N次方Y压缩效应.2)态|ψ₅⁽²⁾>_q所分别呈现的任意奇数阶和任意偶数阶的等阶N次方Y压缩效应,其压缩条件、压缩特征以及压缩程度和压缩深度等各不相同.3)无论压缩阶数N取奇还是取偶,态|ψ₅⁽²⁾>_q的第一和第二这两个正交分量的等阶N次方Y压缩效应总是呈现出周期性的互补关系.     

第Ⅴ类两态叠加多模叠加态光场的等阶N次方H压缩特性研究

本文构造了由多模真空态|{O_j}〉q和多模虚相干态的相反态|{-iZ_j}〉q这两者的线性叠加所组成的第Ⅴ类两态叠加多模叠加态光场ψ₅⁽²⁾〉q,利用多模压缩态理论详细研究了态 ψ₅⁽²⁾〉q的广义非线性等阶N次方H压缩特性.结果发现:1)态ψ₅⁽²⁾〉q是一种典型的多模非经典光场;无论腔模总数q与压缩阶数N这两者之积q·N取奇还是取偶,只要各模的初始相位之和 、态间的初始相位之差(θ_nq^(I)－θ_oq^(o))等满足一定的量子化条件,态ψ₅⁽²⁾〉q总可分别呈现出周期性变化的、任意的奇数模-奇数阶、奇数模-偶数阶、偶数模-偶数阶和偶数模-奇数阶这四种不同形式的等阶N次方H压缩效应.2)上述四种不同形式的等阶N次方H压缩效应,其态间压缩条件完全相同,但模间压缩条件完全不同,结果使其压缩幅度、压缩结果和压缩特性等各不相同.3)无论q·N取奇还是取偶,态ψ₅⁽²⁾〉q的第一和第二这两个正交分量的等阶N次方H压缩效应总是呈现周期性的互补关系.     

On the complete integrability of completely integrable systems

The question of complete integrability of evolution equations associated ton×n first order isospectral operators is investigated using the inverse scattering method. It is shown that forn>2, e.g. for the three-wave interaction, additional (nonlinear) pointwise flows are necessary for the assertion of complete integrability. Their existence is demonstrated by constructing action-angle variables. This construction depends on the analysis of a natural 2-form and symplectic foliation for the groupsGL(n) andSU(n).Research supported by NSF grants DMS-8916968 and DMS 8901607     

Effect of magnetic field on nonlinear interactions of electromagnetic and surface waves in a plasma layer

Investigation is made for nonlinear interaction between incident radiation and a surface wave in a magnetized plasma layer. Both interacting waves are ofP polarization. We get the generated currents and fields at combination frequencies analytically. Unlike theS-polarized interacting waves, the magnetic field affects the fundamental waves and leads to an amplification of generated waves when their frequencies approach the cyclotron frequency.     

Nonlinear effects and the transformation of wave energy in an inhomogeneous plasma

This paper discusses the problem: under what conditions does the quasilinear transformation of waves in plasma with an inhomogeneous beam remain a dominant effect if the nonlinear interaction of waves is respected. It is shown that in the region of densities _p ² _B ² the nonlinear interaction between the high-frequency and the newly excited waves can already affect the initial stage of the process and can result in the establishment of the Rayleigh-Jeans distribution for the two groups of waves. If, on the other hand, the low-frequency waves grow first with a quasilinear increment, the nonlinear transformation of energy inside a group of low-frequency waves is again apt to affect substantially their final amplitude and thus also the total amount of energy that can be transformed into those waves. The conditions under which a particular nonlinear effect predominates are derived for various characteristic values of the density of a cold plasma.