Electronic structure and magnetic phase transition in MnSi

Temperature variations of the amplitude of zero-point and thermal spin fluctuations in a helicoidal ferromagnetic (MnSi) are characterized using the electronic structure model that follows from ab initio LDA + U + SO calculations. It is found that a drastic reduction in the amplitude of zero-point spin fluctuations at temperature T _S (in the vicinity of the magnetic phase transition) leads to ferromagnetic solution instability (a change in the sign of the intermode interaction parameter). The observed magnetovolume effect and a sharp change in the radius of spin correlations have the same underlying cause. The results of calculation of the volumetric coefficient of thermal expansion agree well with the observed anomaly in the region of the magnetic phase transition.     

Emergence of advance waves in a steady-state universe

In standard Wheeler-Feynman electrodynamics advanced waves from any source are absolutely canceled by the advanced waves from the absorber responding to that source. The present work shows this cancellation fails over cosmic distances in a steady-state universe. A test of the view proposed earlier, in a paper which assumed failure of cancellation and hoc, that zero-point fluctuations of the electromagnetic field are such emergent advanced waves, is posed. The view entails anomalous slowing of spontaneous transition rates at longer emission wavelengths; available data go against this, furnishing additional argument against the suspect assumption that the universe is steady-state.     

Zero-point momentum in complex media

In this work we apply field regularization techniques to formulate a number of new phenomena related to momentum induced by electromagnetic zero-point fluctuations. We discuss the zero-point momentum associated with magneto-electric media, with moving media, and with magneto-chiral media.     

Temperature resolution of microwave radiometers

We consider the quantum limits of the radiometer sensitivity in power and spectral density measurements of the radio emission. It is shown that taking into account zero-point field fluctuations makes it possible to resolve some paradoxes in the theory of an ideal radiometer. We estimate the limiting temperature resolution achieved when the entire spectrum of thermal radio emission is integrated. The sensitivity of a detector radiometer is analyzed with allowance for the thermal noise of the nonlinear element. The results of calculations are compared with the experimental data. State University of Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 7, pp. 824–835, July, 1997.     

First-principles study of the temperature-pressure phase diagram of BaTiO3

We investigate the temperature-pressure phase diagram of BaTiO3 using a first-principles effective-Hamiltonian approach. We find that the zero-point motion of the ions affects the form of the phase diagram dramatically. Specifically, when the zero-point fluctuations are included in the calculations, all the polar (tetragonal, orthorhombic, and rhombohedral) phases of BaTiO3 survive down to 0 K, while only the rhombohedral phase does otherwise. This behavior results from a practical equivalence between thermal and quantum fluctuations. Our work confirms the essential correctness of the phase diagram proposed by Ishidate et al. [Phys. Rev. Lett. 78, 2397 (1997)]].     

Einstein-Ehrenfest's radiation theory and Compton-Debye's kinematics

Einstein and Ehrenfest's radiation theory is modified in order to take into account the effects of the random zero-point fields, characteristic of classical stochastic electrodynamics, in a system of classical molecules interacting with thermal radiation. This is done by replacing the Einstein concept of random spontaneous emission by the concept of stimulated emission by the random zero-point fields. As a result, Compton and Debye's kinematic relations are obtained within the realm of a completely classical theory, that is, without having to consider the wave-particle duality for the molecules or the radiation.     

Spontaneous emission in cavities: How much more classical can you get?

Cavity-induced changes in atomic spontaneous emission rates are often interpreted in terms of quantum electrodynamical zero-point field fluctuations. A completely classical method of computing this effect in terms of the unquantized normal mode structure of the cavity is presented here. Upon applying the result to a classical dipole radiating between parallel mirrors, we obtain the same cavity correction as that for atomic spontaneous emission in such a cavity. The theory is then compared with a recent experiment in the radio-frequency domain.It is a pleasure and an honor to dedicate this paper to Professor Asim O. Barut, who, as my teacher, advisor, and friend, has been a great inspiration to me as well as many, many others.Work supported by the National Research Council of the United States.     

Parametric frequency conversion in layered nonlinear media

Frequency-angular distributions of signal wave intensity are calculated for spontaneous parametric down-conversion and parametric frequency conversion in spatially nonuniform nonlinear media. Wave reflection from interfaces is taken into account, and both regular and irregular nonuniform distributions of second-order nonlinear susceptibility are considered. A unified approach using a scattering matrix and a generalized Kirchhoff law is applied in calculations of spontaneous and stimulated processes in dissipative nonlinear media. Interference of electromagnetic zero-point fluctuations of the vacuum, nonlinear interference, and nonlinear diffraction are examined for media with various absorptive properties. Theoretical foundations are developed for diagnostics of nonuniform distributions of the second-order susceptibility, based on measurement of the line profiles of nonlinear signals.     

Spin fluctuations and electronic semiconductor-metal transitions in iron monosilicide

This paper discusses the effect of dynamic zero-point and thermal spin-density fluctuations (SDF) on the electronic spectrum of the nearly-ferromagnetic semiconductor FeSi. It is shown that near T=0° zero-point SDF can lead to so much splitting of the electron states of the valence and conduction band that a “gapless” ground state arises. As the temperature increases, the forbidden gap in the spectrum of d electrons first reappears due to suppression of zero-point fluctuations and then disappears again, as the amplitude of thermal spin fluctuations increases. It is these transformations of the electronic spectrum that are the reason for the anomalous changes in the magnetic susceptibility with temperature observed experimentally. Fiz. Tverd. Tela (St. Petersburg) 40, 1437–1441 (August 1998)     

On the Spectral Distribution of Equilibrium Radiation and Zero-Point Fluctuations in the Coulomb System

The consideration of equilibrium radiation in plasma-like media shows that the spectral energy distribution of such radiation differs from that of Planck equilibrium radiation. Based on the previously derived relation for the spectral energy density of equilibrium radiation in the system of charged particles, accounting for finite damping in a medium with spatial dispersion, the limiting case of infinitesimal damping dispersion is considered. It was shown that zero-point vacuum fluctuations being a component of the total spectral energy distribution in the medium should be renormalized when using certain models for the transverse plasma permittivity. In this case, renormalized zero-point vacuum fluctuations become dependent on plasma parameters. The possibility of the manifestation of this effect is discussed.     

Quantum limits of cold damping with optomechanical coupling

Thermal noise of a mirror can be reduced by cold damping. The displacement is measured with a high-finesse cavity and controlled with the radiation pressure of a modulated light beam. We establish the general quantum limits of noise in cold damping mechanisms and we show that the optomechanical system allows to reach these limits. Displacement noise can be arbitrarily reduced in a narrow frequency band. In a wide-band analysis we show that thermal fluctuations are reduced as with classical damping whereas quantum zero-point fluctuations are left unchanged. The only limit of cold damping is then due to zero-point energy of the mirror. Received 1st August 2001 and Received in final form 12 October 2001     

有源LC回路量子化后的波函数

从路径积分的方法出发，采用高斯型传播子，得出了有源ＬＣ回路量子化后的严格波函数，并讨论了电荷，电流，能量的零点起伏。     

阻尼谐振子的严格波函数

对与速度成正比的阻尼谐振子，通过正则变换，采用路径积分方法，得出了阻尼谐振子的严格波函数，还讨论了阻尼谐振子的坐标、动量的零点涨落. 关键词：     

Estimate of Planck's Constant from an Electromagnetic Mach Principle

An electromagnetic Mach principle is introduced, considering the zero-point radiation field as being produced by all visible matter in the universe, and at the same time being responsible for the quantum fluctuations of matter. An order-of-magnitude estimate allows thus to derive a relation between Planck's constant (as a measure of the strength of the field fluctuations) and cosmological constants, which is well satisfied by the accepted values of the intervening quantities.     

双色驻波场中梯形三能级原子所受整流偶极力的涨落分析

本文基于文献[1]利用双色驻波场作用于三能级原子获得宏观数量个光学波长上符号保持不变的整流偶极力的工作基础上,运用量子回归定理计算了所得整流偶极力在一个光学波长上的涨落.结果表明:原子偶极零点振动与光场幅度梯度相互作用引起的偶极力的涨落D1的值较大,是整流偶极力涨落的主要因素,且其随空间的变化规律与整流偶极力相似;原子偶极与真空零点振动相互作用导致偶极力的涨落Ds较小,几乎可以忽略不计.由于力的起伏所导致的加热效应不利于中性原子的偶极束缚[6].     

Zero-Point Energy of Quantum Fields in a Schwarzschild Geometry

The effective Lagrangian and the zero-point (or Casimir) energy is calculated from the zeta-function which is obtained by the heat kernel method using the expansion of (Bormann and Antonsen, 1995). Calculated this way this unavoidable energy contribution is automatically regularised and ready for further investigation. Interesting observations include a large energy contribution (from scalar field and fermionic zero-point fluctuations) that is non-zero as the mass goes to zero, perhaps indicating a topological origin. Also, plots of the contribution of gauge boson fields to the zero-point energy, as a function of radial distance (gravitational field strength) and the size of the gauge boson coupling (gauge field strength) shows great variation, notably the occurrence of resonances.     

Spin correlations and magnetic order in nonsuperconducting Nd(2-x)Ce(x)CuO(4+/-delta)

We report quantitative neutron scattering measurements of the evolution with doping of the Néel temperature, the antiferromagnetic correlations, and the ordered moment of as-grown, nonsuperconducting Nd(2-x)Ce(x)CuO(4+/-delta) (0相似文献   

On gravitational fluctuations of quantum vacuum interacting with photons

An upper bound for the photon mass is calculated by regarding photons under the action of a gravitational field within the framework of fluctuations in the quantum vacuum. Furthermore, some considerations upon zero-point energy are made in order to estimate interaction range in terms of distance.