On the rotation of the universe

We consider different interpretations of the rotation of the metagalaxy and cosmological models of the universe with rotation. The Muradyan formula for the angular momentum of the metagalaxy is obtained, starting from the hierarchic concept of reality. It is established that the angular velocities of rotation of matter in the Gedel and Ozsvath-Schücking models of the universe have the same order 10^–11 rad/year. Possible local effects of a rotating universe are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 22–25, January, 1985.     

Dynamics of Inflationary Universes with Positive Spatial Curvature

If the spatial curvature of the universe is positive, then the curvature term will always dominate at early enough times in a slow-rolling inflationary epoch. This enhances inflationary effects and hence puts limits on the possible number of e-foldings that can have occurred, independently of what happened before inflation began and in particular without regard for what may have happened in the Planck era. We use a simple multi-stage model to examine this limit as a function of the present density parameter ₀ and the epoch when inflation ends.     

On the global geometry of the stephani universe

A preliminary investigation of global properties of the Stephani solution of the Einstein field equations is presented. This solution generalizes those of Friedman-Robertson-Walker (FRW) in such a way that the spatial curvature indexk (a constant in the FRW models) is a function of the time coordinate. The de Sitter solution, which is also a special case of the Stephani solution, is analyzed in the Stephani coordinates to gain insight into the global structure of the manifold and its foliation. The general metric is found to have several properties in common with this example. It has singularities which can be avoided either by matching the solution to an (as yet unknown) empty-space solution or confining the curvature index to be positive at all times.     

Dynamics of the universe with disformal coupling between the dark sectors

We use a dynamical analysis to study the evolution of the universe at late time for the model in which the interaction between dark energy and dark matter is inspired by a disformal transformation. We extend the analysis in the existing literature by assuming that the disformal coefficient depends both on the scalar field and its kinetic terms. We find that the dependence of the disformal coefficient on the kinetic term of scalar field leads to two classes of the scaling fixed points that can describe the acceleration of the universe at late time. The first class exists only for the case where the disformal coefficient depends on the kinetic terms. The fixed points in this class are saddle points unless the slope of the conformal coefficient is sufficiently large. The second class can be viewed as the generalization of the fixed points studied in the literature. According to the stability analysis of these fixed points, we find that the stable fixed point can take two different physically relevant values for the same value of the parameters of the model. These different values of the fixed points can be reached for different initial conditions for the equation of state parameter of dark energy. We also discuss the situations in which this feature disappears.     

Spiral galaxies rotation curves with a logarithmic corrected newtonian gravitational potential

We analyze the rotation curves of 10 spiral galaxies with a newtonian potential corrected with an extra logarithmic term. The logarithmic correction can have its origin from fundamental frameworks, like string theories or effective models of gravity due to quantum effects. There is also a connection with some toy models resulting from TeVeS. We represent the spiral galaxies as a thin disk. There is a new constant associated with the extra term in the potential. The rotation curve of the chosen sample of spiral galaxies is well reproduced for a narrow range of the new constant. The compatibility of this correction with local physics is discussed.     

The development of perturbations in the universe described by the nonstationary equation of state

The growth of the perturbation density in a baryon substance due to a nonstationary character of the equation of state of nonbaryon matter in the Universe is studied. It is shown that the perturbations evolve slower than within the Friedmann cosmological model. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 61–67, March, 2009.     

Slow rotation of compressible viscous fluid in cosmological universe

New analytic solutions for rotational perturbations of the Robertson-Walker metric are found in order to incorporate the possibility of a rotating viscous universe. The field equations impose restrictions on the matter rotationω(r, t), and some of the solutions for Ω(r, t) which is related to the local dragging of inertial frames are studied. In all the cases the rotational velocity is found to decay with increase of time. Geodesics of the metric are studied to reveal the intrinsic nature of rotation and to elucidate the role of Ω.     

On the evolution of global strings in the early universe

We find that a bent global string straightens itself out by dissipation into Nambu-Goldstone (NG) bosons in the order of one oscillation time and that the spectrum of radiated NG bosons is 1/k. In the early universe, the assumption that there is one global string per causal horizon is justified after an initial period during which the effect of the primordial plasma on the motion of the strings is non-negligible. We find that the upper bound that axion radiation by strings places on the axion decay constant is comparable to, but not more stringent than the one derived from coherent oscillations of the axion field, i.e. ∫_a ≲ 10¹²GeV. We also discuss the model-dependence of this bound.     

Beam alignment with the axis of a rotation stage for laser fabrication of microcircular structures

An optical technique to align laser beam with the axis of a rotating stage is proposed for laser fabrication of circular microstructures. The laser beam is first aligned parallel to the rotation axis and subsequently adjusted to coincide with the axis. An optical arrangement consisting of two quadrant photodiodes for the x- and y-directions and a specially designed beam splitter is utilized for the alignment. Mathematical modeling of the alignment system is carried out to estimate alignment errors caused by misalignment of mirror surfaces in the beam path. It is shown that parallelness of the laser beam to the rotation axis is a key factor to reduce alignment errors. The proposed method was applied to a microstereolithography system and proved that the laser beam can be aligned within a distance of about 25 μm from the rotation axis.     

Effect of rotation of the universe on the relative position angle of radiosources

The effect of the space-time curvature on the relative position angle between the vector of radio waves and the direction of maximum elongation of an extended radiosource is studied during propagation of radiation from the source to the observer. A detailed analysis is carried out for the Gödel type cosmological model. It is found that the rotation of the Universe cannot induce a Birch-type anisotropy with proportional to cos , where is the angle between the direction of the ray and the rotational axis. An anisotropy with proportional to sin² should be expected. In the case of a Gödel-type model, we have calculated the change in the eccentricity of the ellipse of the source image relative to the eccentricity of the real object.M. Gorky State University, Perm' Branch of Theoretical Problems, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 3–8, June, 1992.     

Dynamics of quantum discord in the purification process

We investigate the dynamics of quantum discord during the purification process. In the case of Werner states, it is shown that quantum discord is increased after a round of purification protocol. Furthermore, quantum mutual information and classical correlation is also increased during this process. We also give an analytic expression for a class of higher dimensional states which have additive quantum discord.     

Mesoscopic Simulation of Polymers in Fluid Dynamics Problems

Dissipative Particle Dynamics has been used effectively as a modelling technique to perform Computational Fluid Dynamics. DPD preserves some molecular detail whereas in classical CFD this is lost. The technique has been tested in two cases of macromolecules in flow simulations. First, the behaviour of a polymer within a square capillary has been studied, which is the basis of hydrodynamic chromatography. Secondly, the effect of polymers on the melting in shear flow has been simulated.     

Dynamics of quasicrystals

The (lattice) dynamics of quasicrystals differs in many aspects from that of lattice periodic systems. This they have in common with other aperiodic crystals. The dynamics of quasicrystals is discussed here in the context of these general aperiodic crystals, but the special features of quasicrystals are stressed. The lattice dynamics is now fairly well understood. Especially for aperiodic crystals, there are excitations related to the possibility to describe the systems in superspace. These ‘phasons’ are discussed in particular.     

计及声子辅助跃迁的单量子点中的非线性法拉第偏转

利用一束弱线性π偏振探测光在与其平行的磁场作用下所形成的两偏振分量,在半导体单量子点中考虑声子辅助跃迁去构建环形四能级电磁感应透明介质模型.利用多重尺度法,解析研究发现:仅考虑系统的线性效应,随着耦合光强度的增加,介质对探测光的吸收迅速减少,形成透明窗口,并且透明窗口的宽度随之增大;进一步地,在相同的外加磁场下探测光的非线性法拉第偏转方向与线性法拉第偏转相反,且偏转角更大.随着声子辅助跃迁强度的增加,线性和非线性法拉第偏转角都会逐渐变小,并且非线性法拉第偏转角减小的更多.这说明系统中的声子辅助跃迁能有效地调制探测光的法拉第偏转.我们的研究可能对于弱光条件下的光信息处理和传输具有潜在的应用价值.     

Pressure Effect on Solvation Dynamics and Rotational Dynamics in Solution

Effects of pressure on solvation dynamics and rotational dynamics in solution were studied by picosecond time-dependent fluorescence Stokes shift (TDFSS) and picosecond time-dependent fluorescence rotational depolarization (TDFRD). The fluorescence lifetimes of solute probes, coumarin 153 and p -terphenyl, in various solvents were measured at high pressures by time-correlated single photon counting (TCSPC) technique with time resolution of 20-30 ps.     

Dynamics of harmonically-confined systems: Some rigorous results

In this paper we consider the dynamics of harmonically-confined atomic gases. We present various general results which are independent of particle statistics, interatomic interactions and dimensionality. Of particular interest is the response of the system to external perturbations which can be either static or dynamic in nature. We prove an extended Harmonic Potential Theorem which is useful in determining the damping of the centre of mass motion when the system is prepared initially in a highly nonequilibrium state. We also study the response of the gas to a dynamic external potential whose position is made to oscillate sinusoidally in a given direction. We show in this case that either the energy absorption rate or the centre of mass dynamics can serve as a probe of the optical conductivity of the system.     

Fluorescence Dynamics of Three UV-B Sunscreens

Polarity of the surrounding medium affects the excited states of UV-B sunscreens. Therefore understanding excited state processes in a mixed polarity model system similar to skin is essential. We report the excited state lifetimes, quantum yields, radiative and non-radiative rates of three sunscreens. Among the three UV-B sunscreens studied, octyl salicylate emits from a single excited state, while padimate O and octyl methoxy cinnamate show multiple states. The radiative rates of salicylate and cinnamate are approximately constant, while that of padimate O depends strongly on solvent. The non-radiative rates of all sunscreens vary with solvent polarity. Compared to salicylate and cinnamate, padimate O is complex to analyze because of its two emission peaks and one peak’s strong dependence on the dielectric constant. High absorbance, broad absorption peak with small fluorescence quantum yield, and low radiative rate make octyl methoxy cinnamate a superior UV-B sunscreen ingredient. The complexity in excited-state analysis shows that the lifetimes of the sunscreens are critical parameters, in addition to absorbance and quantum yield. Fluorescence lifetime substantiates the use of polystyrene nanospheres as a model host to study the photo-physical properties of sunscreen in a heterogeneous environment.     

Dynamics of the mixmaster-type vacuum universe with geometryR×S 3×S 3×S 3

A model of a spatially homogeneous and anisotropic, vacuum universe with geometryR×S ³×S ³×S ³ is studied using a hamiltonian formalism. The formalism is developed by first deriving the hamiltonian for aD-dimensional, mixmaster-type, vacuum universe. The model evolves from an initial Kasner-like state to a final Kasner-like state upon irreversible collapse. The collapse is predicted to be inevitable based on qualitative analysis and numerical calculations verify this behavior. A lower bound of 0.286 is found for the ratio of the contraction rate of the universe long after a Kasner phase transition to the contraction rate long before the transition. Seven of the seventeen theoretically possible qualitatively different compactification schemes are found numerically and tabulated. A subset of all the constraint satisfying initial conditions which leads to three isotropically expanding dimensions and six contracting dimensions is found.     

Qualitative analysis of molecular rotation starting from inter-nuclear potential

We study how qualitative features of the molecular rotational dynamics can be derived directly from the internuclear (vibrational) potential. This approach is presented on the example of a tetrahedral molecule A₄ using several increasingly elaborated models of the potential. Received: 16 February 1999 / Received in final form: 4 May 1999