The distribution function for a subsystem experiencing temperature fluctuations

A nonlinear generalization of the Landau-Lifshitz theory of hydrodynamic fluctuations for the simplest case in which only energy flux and temperature fluctuations are observed is used to derive the distribution function for a subsystem with a fluctuating temperature, which coincides with the Levy distribution taken to be one of the main results of the so-called Tsallis’s nonextensive statistics. It is demonstrated that the same distribution function is obtained from the principle of maximum of information entropy if the latter is provided by Renyi’s entropy, which is an extensive quantity. The obtained distribution function is to be used instead of the Gibbs distribution in constructing the thermodynamics of systems with significant temperature fluctuations.     

Crystal Structure Phase Transitions in the Perovskites A(Cu1−xMnx)Mn4O12(A = Na+, Ca2+, Y3+, La3+)

X-Ray diffraction and neutronographical studies on the crystal structure of the perovskitelike compounds A(Cu_1−xMn_x)Mn₄O₁₂ have been undertaken. It has been shown that the samples with 50% of Mn³⁺ in the octahedral sites have a cubic unit cell, while the samples with higher Mn³⁺ composition may have a monoclinic or rhombohedral unit cell. The temperature increase raises the symmetry to the cubic one. The concentration ranges with different symmetry type have been determined. The lowering of the symmetry of the unit cell is due to the cooperative Jahn-Teller effect.     

Entropy of open quantum systems and the Poisson distribution

The entropies of a harmonic oscillator and a quantum Klein-Gordon-Fock field with a static source are found in the coherent state. In both cases, the obtained expressions coincide up to a numerical factor with the Bekenstein-Hawking entropy for a black hole or, more precisely, for the physical vacuum around the hole. Such a coincidence and the property of a gravitational field to make a quantum system placed in this field decoherent lead to the assumption that the vacuum in the vicinity of a black hole is in a coherent state. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 123, No. 1, pp. 107–115, April, 2000.     

Influence of anionic substitutions on hyperfine interactions and ionic ordering in ferrites

Hyperfine Interactions -     

Structure and Properties of Solid Solutions in the System YBaCuFeO<Subscript>5</Subscript>-YBaCuCoO<Subscript>5</Subscript>

The crystal structure parameters of solid solutions YBaCuFe_{1 − x} Co_xO₅ (0 ≤ x ≤ 1) were determined, and their thermal stability, thermal expansion, conductance, thermoelectromotive force, dielectric properties, and magnetic sensibility were studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 5, 2005, pp. 716–720.Original Russian Text Copyright © 2005 by Chizhova, Klyndyuk, Bashkirov, Petrov, Yanushkevich.     

Theoretical Calculation of Products Distribution in the Reaction of Atomic Carbon with Pyridine

The elementary reaction of atomic carbon C(³P) with pyridine C₅H₅N is studied using quantum-mechanical calculations of the electronic structure and statistical calculations on the potential energy surface of the C6H5N triplet state. At least two most probable reaction ways associated with hydrogen atom abstraction reaction are revealed. The important role of the molecular fragmentation channel, including acetylene C₂H₂ molecule abstraction, is also shown.     

Entanglement Between Two Dipole-Coupled Qubits Interacting with Two Independent Slightly Detuned Cavity Modes

Considering the generalized double Jaynes-Cummings model, we examine the entanglement between two non-identical dipole-dipole coupled qubits interacting with two independent detuned vacuum cavity modes. We calculate the negativity as a measure of qubits entanglement. We find that entanglement parameter evolve periodically with time and the period are affected by the model parameters and initial states of qubits. For unentangled initial states the detuning and dipole-dipole interaction affect only the period of entanglement oscillations, not the maximum value of entanglement. For entangled states the detuning stabilizes the entanglement parameter oscillations. According to choice of initial entangled state the dipole-dipole strength is greatly enhances or weakens the oscillations of the entanglement parameter.

     

The influence of high-temperature annealing of electrochemically deposited Cu-Zn-Sn layers on the composition and structure of kesterite films — absorbing layers of solar cells

Russian Chemical Bulletin - Cu1?δZn2?xSnxS4 (CZTS) films were prepared by sequential electrochemical deposition on different supports (Ta, Ti, Mo, and glass—Mo). The samples...