Entropy maximum in a nonlinear system with the 1/<Emphasis Type="Italic">f</Emphasis> fluctuation spectrum

Analysis of the control and subordination is carried out for the system of nonlinear stochastic equations describing fluctuations with the 1/f spectrum and with the interaction of nonequilibrium phase transitions. It is shown that the control equation of the system has a distribution function that decreases upon an increase in the argument in the same way as the Gaussian distribution function. Therefore, this function can be used for determining the Gibbs-Shannon informational entropy. The local maximum of this entropy is determined, which corresponds to tuning of the stochastic equations to criticality and indicates the stability of fluctuations with the 1/f spectrum. The values of parameter q appearing in the definition of these entropies are determined from the condition that the coordinates of the Gibbs-Shannon entropy maximum coincide with the coordinates of the Tsallis entropy maximum and the Renyi entropy maximum for distribution functions with a power dependence.     

Cosmology based on <Emphasis Type=Italic>f</Emphasis>(<Emphasis Type=Italic>R</Emphasis>) gravity with <Emphasis Type=Italic>O</Emphasis>(1)eV sterile neutrino

We confront different up to date cosmological data with different gravity models of the Universe with one additional massive sterile neutrino [1].     

An entropy-based stability analysis of extreme fluctuations in a system featuring a 1/<Emphasis Type=Italic>f</Emphasis> spectrum

Extreme fluctuations are modeled by a point system of stochastic equations, in which power spectra inversely proportional to the frequency are produced under the effect of white noise. The distribution of extreme fluctuations corresponds to the maximum of statistical entropy, which points to their stability in nature. By calculating the spectral entropy of random processes, it becomes possible to investigate their stability directly from power spectra without the need to calculate the amplitude distribution functions. The spectral entropy as a function of white noise amplitude has a minimum. The position of the spectral entropy minimum corresponds to the critical state of the system in which the spectra of fluctuating quantities are inversely proportional to the frequency.     

Manifestation of 1/<Emphasis Type=Italic>f</Emphasis> leakage noise in nanoscale light-emitting structures

We present the results of studies of the 1/f noise spectrum in light-emitting diodes and lasers with nanoscale structures based on GaAs and its solid solutions. Leakage current was detected from an analysis of I–V characteristics and voltage noise spectrum dependences on the current. Leakage current appeared to be the main source of noise in the samples and leads to intensity fluctuations of the spontaneous radiation. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 2, pp. 149–161, February 2008.     

<Emphasis Type=Italic>Y</Emphasis> and <Emphasis Type=Italic>Z</Emphasis> luminescence of polycrystalline cadmium telluride

The properties of polycrystalline CdTe with a grain size of 5–30 μm have been investigated using the microphotoluminescence methods of spectral analysis and topography. This material has been prepared by direct synthesis in a vapor flow of components at a low temperature. The dominance of the Y and Z bands in the spectra reflects a nonequilibrium character of the crystallization processes. The superlinear dependences of the luminescence intensity on the level of the band-to-band excitation indicate the exciton nature of the corresponding transitions. The activation energies for temperature quenching of luminescence in the temperature range T = 100–150 K are found to be 120 meV for the Y luminescence and 180 meV for the Z luminescence, which correspond to the dissociation of excitons bound to defects with the transition of charge carriers to the conduction and valence bands. The monochromatic topography data indicate that Y and Z defects have different material bases.     

4<Emphasis Type=Italic>s</Emphasis>-1<Emphasis Type=Italic>s</Emphasis> two-photon decay in hydrogen atom with allowance for cascades

The 4s-1s two-quantum decay in the hydrogen atom is calculated in the framework of quantum electrodynamics with allowance for cascades. It is shown that the pure two-photon contribution cannot be separated from the contribution of cascade processes. Interference between the transitions of these two types is comparable in magnitude with the pure two-photon contribution. The separation of pure two-photon contributions is discussed recently in connection with the role of two-photon decays in the separation of radiation from matter in the early Universe.     

Static spherically symmetric solutions in <Emphasis Type=Italic>F</Emphasis>(<Emphasis Type=Italic>R</Emphasis>) gravity

A Lagrangian derivation of the Equations of Motion (EOM) for static spherically symmetric metrics in F(R) modified gravity is presented. For a large class of metrics, our approach permits one to reduce the EOM to a single equation and we show how it is possible to construct exact solutions in F(R)-gravity. All known exact solutions are recovered. We also exhibit a new non-trivial solution with non-constant Ricci scalar.     

Oxide glasses doped with 3<Emphasis Type=Italic>d</Emphasis> and 4<Emphasis Type=Italic>f</Emphasis> elements (Transparent Magnets): Structure,magneto-optics,magnetic resonance

Glasses of composition Al₂O₃-K₂O-GeO-B₂O₃ doped with rare earths Tb, Dy, Ho, Yb, Gd were investigated. After thermal treatment, magnetic nanoparticles appeared with a structure that could not be identified unambiguously using electron microscopy and electron micro diffraction. Study of the magnetic circular dichroism revealed the structure of the forming nanoparticles to be similar to that of the spinel γ-Fe₂O₃. The high values of the remnant Faraday effect allow us to consider the investigated glasses as transparent permanent magnets.     

Optical detection of an electric field in a GaAs/AlGaAs <Emphasis Type=Italic>n</Emphasis>-<Emphasis Type=Italic>i</Emphasis>-<Emphasis Type=Italic>n</Emphasis> heterostructure with double quantum wells

Processes occurring when a static transverse electric field is applied to a GaAs/AlGaAs n-i-n heterostructure with single quantum wells and asymmetric tunnel-coupled double quantum wells have been investigated by optical methods. The difference between the energies of exciton transitions for quantum wells of different widths makes it possible to attribute the observed photoluminescence peaks to particular pairs of wells or particular single quantum wells. The local electric field for each quantum well has been determined in terms of the Stark shift and splitting of exciton lines in a wide range of external voltage. A qualitative model has been proposed to explain the nonmonotonic distribution of the electric field over the depth of the heterostructure.