Thermal Fluctuations and Electromagnetic Noise Spectra in Quantum Statistical Mechanics.

We derive the thermal noise spectrum of the of the longitudinal and transverse electric field operator of a given wave vector starting from the quantum-statistical definitions and relate it to the complex frequency and wave vector dependent complex conductivity in a homogeneous, isotropic system of electromagnetic interacting electrons. No additional assumptions were used in the proof. We analyze separately the longitudinal and transverse case with their peculiarities. The Nyquist formula for vanishing frequency and wave vector, as well as its modification for non-vanishing frequencies and wave vectors follow immediately. Furthermore we discuss also the noise of the photon occupation numbers.

METHOD OF EXCITATION OF QUASI LONGITUDINAL ACOUSTIC WAVES IN LAYERED STRUCTURES

The analysis of methodological possibilities of excitation of quasi-longitudinal (QL) acoustic waves of the megahertz frequency range in layered structures GaN-on-sapphire is studied and carried out. Volume-type transducers polarized by plate thickness are used to generate and detect QL waves. It is concluded that quasilongitudinal modes (QL) can be excited by this method – the so-called Anisimkin (AN) waves, for which the displacement plane is localized in the film plane and the displacement direction is directed along the wave vector.

Nanoantennas Inversely Designed to Couple Free Space and a Metal–Insulator–Metal Waveguide

The metal–insulator–metal (MIM) waveguide, which can directly couple free space photons, acts as an important interface between conventional optics and subwavelength photoelectrons. The reason for the difficulty of this optical coupling is the mismatch between the large wave vector of the MIM plasmon mode and photons. With the increase in the wave vector, there is an increase in the field and Ohmic losses of the metal layer, and the strength of the MIM mode decreases accordingly. To solve those problems, this paper reports on inversely designed nanoantennas that can couple the free space and MIM waveguide and efficiently excite the MIM plasmon modes at multiple wavelengths and under oblique angles. This was achieved by implementing an inverse design procedure using a topology optimization approach. Simulation analysis shows that the coupling efficiency is enhanced 9.47-fold by the nanoantenna at the incident wavelength of 1338 nm. The topology optimization problem of the nanoantennas was analyzed by using a continuous adjoint method. The nanoantennas can be inversely designed with decreased dependence on the wavelength and oblique angle of the incident waves. A nanostructured interface on the subwavelength scale can be configured in order to control the refraction of a photonic wave, where the periodic unit of the interface is composed of two inversely designed nanoantennas that are decoupled and connected by an MIM waveguide.

Frequencies analysis in an infinite beams array

This model consists of a periodic structure formed by solid beams equidistant from each other submerged in a fluid. The beams are clamped at both ends. The distance between the beams, the elastic properties of the solid and the fluid; and the geometric parameters of the beams determine a relationship between the frequencies of the mechanical waves that can propagate through the structure and the wave vector. Analysis within the first Brillouin zone with the Bloch periodicity condition gives rise to frequency bands in which there is the propagation of mechanical waves and bands in which no waves are propagated. Some propagation bands and forbidden regions were found in the examined frequency ranges for various geometric configurations.

The ground states and the first radially excited states of D-wave vector ρ and ϕ mesons

In this paper, we first derive two QCD sum rules QCDSR I and QCDSR II which are, respectively, used to extract observable quantities of the ground states and the first radially excited states of the D-wave vector [Formula: see text] and [Formula: see text] mesons. In our calculations, we consider the contributions of vacuum condensates up to dimension-7 in the operator product expansion. The predicted masses for [Formula: see text] [Formula: see text] meson and [Formula: see text] [Formula: see text] meson are consistent well with the experimental data of [Formula: see text]([Formula: see text]) and [Formula: see text]([Formula: see text]), respectively. Besides, our analysis indicates that it is reliable to assign the recent reported [Formula: see text]([Formula: see text]) state as the [Formula: see text] [Formula: see text] meson. Finally, we obtain the decay constants of these states with QCDSR I and QCDSR II. These predictions are helpful not only to reveal the structure of the newly observed [Formula: see text]([Formula: see text]) state, but also to establish [Formula: see text] meson and [Formula: see text] meson families.

Thermal Fluctuations and Electromagnetic Noise Spectra in Quantum Statistical Mechanics

We derive the thermal noise spectrum of the Fourier transform of the electric field operator of a given wave vector starting from the quantum-statistical definitions and relate it to the complex frequency and wave vector dependent complex conductivity in a homogeneous, isotropic system of electromagnetic interacting electrons. We analyze separately the longitudinal and transverse case with their peculiarities. The Nyquist formula for vanishing frequency and wave vector, as well as its modification for non-vanishing frequencies and wave vectors follow immediately. Furthermore we discuss also the noise of the photon occupation numbers. It is important to stress that no additional assumptions at all were used in this straightforward proof.

The formation of strip-like vortex motion by surface gravity waves

We studied experimentally the generation of vortex flow by non-collinear gravity waves with a frequency of 2.34 Hz. The vortices formed on the water surface have the form of stripes, the width L=π/(2k sin θ) of which is determined by the wave vector k and the angle between them, and the length is determined by the size of the system. We demonstrate that the measured dependence Ω(t) can be described within the recently developed model that considers the Eulerian contribution to the generated vortex flow and the effect of surface contamination.

Calculation of the Amplitude of Acoustic Waves in Nanoscale Magnets in an Alternating Magnetic Field Caused by Displacements of Domain Boundaries

This paper proposes an algorithm that utilizes a macroscopic approach to calculate the amplitude of the total acoustic signal generated by an alternating magnetic field in ribbon-shaped nanocrystalline magnets (NCMs) with polydomain nanofibers at reversible displacements of domain boundaries. The calculations are made for the case with the wave vector directed along the magnetic field parallel to the tape plane. At the same time, the influence of anharmonicity on the displacements of the domain boundaries is considered for the carrier frequency. The orientation and frequency dependences for the wave vector and the signal absorption coefficient are found under the assumption that the rotation processes can be neglected. It is shown that the residual internal stresses in the (poly- or monodomain) nanograin NCMs have a significant effect on the absorption coefficient and the amplitude of the generated DG signal. The magnetic anisotropy constants decrease along with the size of the nanograins. In this case, the generation process due to the rotation of the spontaneous magnetization vectors is also significant, which must be considered in relation to the displacement processes. The proposed algorithm for calculating the amplitudes of the signals generated by a nanocrystalline magnet can be used to predict the friction properties of the developed promising NCM and calculate the amplitudes of the generated signals at the carrier frequency and harmonics.