Simulations for terrestrial planets formation

In this paper, the formation of terrestrial planets in the late stage of planetary formation is investigated using the two-planet model. At that time, the protostar formed for about 3 Ma and the gas disk dissipated. In the model, the perturbations from Jupiter and Saturn are considered. Variations of the mass of outer planet, and the initial eccentricities and inclinations of embryos and planetesimals are also considered. Our results show that, terrestrial planets are formed in 50 Ma, and the accretion rate is about 60%–80%. In each simulation, 3–4 terrestrial planets are formed inside “Jupiter” with masses of 0.15–3.6 M _⊕. In the 0.5–4 AU, when the eccentricities of planetesimals are excited, planetesimals are able to accrete material from wide radial direction. The plenty of water material of the terrestrial planet in the Habitable Zone may be transferred from the farther places by this mechanism. Accretion could also happen a few times between two major planets only if the outer planet has a moderate mass and the small terrestrial planet could survive at some resonances over time scale of 10⁸ a. In one of our simulations, commensurability of the orbital periods of planets is very common. Moreover, a librating-circulating 3:2 configuration of mean motion resonance is found. Supported by the National Natural Science Foundation of China (Grant Nos. 10573040, 10673006, 10833001, and 10233020) and the Foundation of Minor Planets of Purple Mountain Observatory     

Role of surface modes in vortex formation in BEC

We study the role of surface modes in the process of vortex formation in harmonically trapped BEC. It is shown that the vortex nucleation and penetration to the inner part of the cloud occur at velocities slightly exceeding the surface mode critical velocity. Surface modes induce ripples of the order parameter; these ripples are then transformed into vortex-antivortex pairs. After this, vortices move to the inner part of the cloud, whereas antivortices go in the opposite direction     

Near infrared reflection spectra of ammonia frost: Interpretation of the upper clouds of Saturn

Models of the uppermost cloud layer on Saturn indicate that the cloud is composed of solid ammonia, with the cloud particles being initially formed at about 150 K, and subsequently transported upward by convection to colder regions of the atmosphere. For the purpose of comparison with Saturn's near-i.r. reflection spectrum, we have obtained laboratory reflection spectra of ammonia frost corresponding to a variety of deposition rates and deposition temperatures.We find that the spectral location of the strong 3 μm absorption band of solid ammonia is highly dependent upon the manner in which the frost layer is formed. For rapid deposition on a 150 K cryosurface, which closely simulates what we believe to be the cloud formation process on Saturn, the band is centered at 3.29 μm. This band location, together with the apparent absence of gaseous ammonia overlying the solid ammonia cloud, is consistent with Saturn's observed reflection spectrum in the vicinity of 3 μm.Comparison of Saturn's reflection spectrum with that of Jupiter, in the vicinity of 1.3 and 1.6 μm, also supports the hypothesis of a Saturnian ammonia ice cloud. Differences in the two observed reflection spectra are interpreted as due to gaseous ammonia absorption bands for Jupiter being replaced by solid ammonia absorption features, at displaced wavelengths, for Saturn.An important conclusion of this study is that, for the purposes of either cloud interpretation or cloud radiation modeling, the polycrystalline phase of solid ammonia, and in turn its spectrum, is highly dependent upon the manner in which the soled is formed.     

Hydrostatic equilibrium and Tsallis’ equilibrium for self-gravitating systems

Self-gravitating systems are generally thought to behavior non-extensively due to the long-range nature of gravitational forces. We discuss a relation between the nonextensive parameter q of Tsallis statistics, the temperature gradient and the gravitational potential based on the equation of hydrostatic equilibrium for self-gravitating systems. It is suggested that the nonextensive parameter in Tsallis statistics has a clear physical meaning with regard to the non-isothermal nature of the systems with long-range interactions. Tsallis’ equilibrium distribution for the self-gravitating systems describes the property of hydrostatic equilibrium of the systems.     

TheB (3) field as a link between gravitation and electromagnetism in the vacuum

The emergence of theB ⁽³⁾ field in vacuo has shown that electromagnetism is non-Abelian and similar in structure to gravitation. In this paper the Christoffel symbol used in general relativity is developed for electromagnetism in curvilinear coordinates: The former becomes describable as the antisymmetric part of the gravitational Ricci tensor. Therefore gravitation and electromagnetism are respectively the symmetric and antisymmetric parts of thesame Ricci tensor within a proportionality factor. Both fields are obtained from the Riemann curvature tensor, both are expressions of curvature in spacetime.     

Centrifugal (centripetal) and Coriolis' velocities and accelerations in $$ (\bar L_n,g) $$ -spaces

The notions of centrifugal (centripetal) and Coriolis' velocities and accelerations are introduced and considered in spaces with affine connections and metrics [ -spaces] as velocities and accelerations of flows of mass elements (particles) moving in space-time. It is shown that these types of velocities and accelerations are generated by the relative motions between the mass elements. They are closely related to the kinematic characteristics of the relative velocity and relative acceleration. The centrifugal (centripetal) velocity is found to be in connection with the Hubble law. The centrifugal (centripetal) acceleration could be interpreted as gravitational acceleration as has been done in the Einstein theory of gravitation. This fact could be used as a basis for workingout new gravitational theories in spaces with affine connections and metrics.     

镁颗粒群着火和燃烧过程数值模拟

建立了一维非稳态球形镁颗粒群的着火燃烧模型, 数值模拟镁颗粒群的着火和燃烧过程, 研究表明, 颗粒群着火首先发生在颗粒群边界, 随后初始的燃烧火焰会分离为两个, 一个向颗粒群内部传播, 一个向外部传播, 最终内部火焰消失, 外部火焰维持并控制着整个颗粒群的燃烧; 内火焰向颗粒群内部传播过程中, 传播速度会逐渐加快, 且火焰温度值呈逐渐降低趋势. 分析了颗粒群内部参数和环境参数对镁颗粒群着火燃烧的影响. 随颗粒浓度的增大, 颗粒群着火时间略有增长, 但火焰传播速度更快, 燃烧稳定时火焰球尺寸也更大. 颗粒群初温越高, 则颗粒群着火时间越短, 火焰传播速度也会加快, 但燃烧稳定时火焰球尺寸基本不变. 环境温度对颗粒群着火燃烧的影响较复杂, 环境温度越高, 颗粒群着火时间越短, 但火焰传播速度却越慢, 燃烧稳定时火焰球尺寸变化很小. 颗粒粒径和辐射源温度对颗粒群着火燃烧的影响较显著, 颗粒粒径越小或辐射源温度越高, 则颗粒群着火时间越短, 火焰传播速度越快, 燃烧稳定时火焰球尺寸也越大. 数值模拟结果与文献中试验结果相一致. 关键词： 粉末燃料冲压发动机 镁着火燃烧 颗粒群     

Studying planet populations by gravitational microlensing

The ‘most curious’ effect of the bending of light by the gravity of stars has evolved into a successful technique unlike any other for studying planets within the Milky Way and even other galaxies. With a sensitivity to cool planets around low-mass stars even below the mass of Earth, gravitational microlensing fits in between other planet search techniques to form a complete picture of planet parameter space, which is required to understand their origin in general, that of habitable planets more particularly, and that of planet Earth especially. Current campaigns need to evolve from first detections to obtaining a sample with well-understood selection bias that allows to draw firm conclusions about the planet populations. With planetary signals being a transient phenomenon, gravitational microlensing is a driver for new technologies in scheduling and management of non-proprietary heterogeneous telescope networks, and can serve to demonstrate forefront science live to the general public.     

Saturn's Great White Spots

The term, Great White Spot, is used for large and unusual atmospheric disturbances on the planet Saturn. The phenomenology has been recorded only in five occasions during the last century, and its evolution can be described in terms of four different phases: (i) Onset (first week), outburst and rapid growth of a very bright cloud up to a size of approximately 20 000 km; (ii) planetary disturbance (相似文献   

Observation of magnetic field-induced contraction of fission yeast cells using optical projection microscopy

The charges in live cells interact with or produce electric fields, which results in enormous dielectric responses, flexoelectricity, and related phenomena. Here we report on a contraction of Schizosaccharomyces pombe (fission yeast) cells induced by magnetic fields, as observed using a phase-sensitive projection imaging technique. Unlike electric fields, magnetic fields only act on moving charges. The observed behavior is therefore quite remarkable, and may result from a contractile Lorentz force acting on diamagnetic screening currents. This would indicate extremely high intracellular charge mobilities. Besides, we observed a large electro-optic response from fission yeast cells.     

The dynamics of charged dust in the general theory of relativity

The spherically symmetric motion of charged dust in its own gravitational field (the analog of Tolman's problem) is investigated. A conclusion is reached about the cessation of the contraction of the charged dust cloud.Translated from Izvestiya VUZ. Fizika, No. 12, pp. 63–67, December, 1973.     

Interactions of charged dust particles in clouds of charges

Two charged dust particles inside a cloud of charges are considered as Debye atoms forming a Debye molecule. Cassini coordinates are used for the numerical solution of the Poisson-Boltzmann equation for the charged cloud. The electric force acting on a dust particle by the other dust particle was determined by integrating the electrostatic pressure on the surface of the dust particle. It is shown that attractive forces appear when the following two conditions are satisfied. First, the average distance between dust particles should be approximately equal to two Debye radii. Second, attraction takes place when similar charges are concentrated predominantly on the dust particles. If the particles carry a small fraction of total charge of the same polarity, repulsion between the particles takes place at all distances. We apply our results to the experiments with thermoemission plasma and to the experiments with nuclear-pumped plasma.     

Simulation of random packing of spherical particles with different size distributions

A numerical model for a loose packing process of spherical particles is presented. The simulation model starts with randomly choosing a sphere according to a pregenerated continuous particle-size distribution, and then dropping the sphere into a dimension-specified box, and obtaining its final position by using dropping and rolling rules which are derived from a similar physical process of spheres dropping in the gravitational field to minimize its gravity potential. Effects of three different particle-size distributions on the packing structure were investigated. Analysis on the physical background of the powder-based manufacturing process is additionally applied to produce optimal packing parameters of bimodal and Gaussian distributions to improve the quality of the fabricated parts. The results showed that higher packing density can be obtained using bimodal size distribution with a particle-size ratio from 1.5 to 2.0 and the mixture composition around n ₂:n ₁=6:4. For particle size with a Gaussian distribution, the particle radii should be limited in a narrow range around 0.67 to 1.5.     

The gravitational bending of light by stars: a continuing story of curiosity,scepticism, surprise,and fascination

Driven entirely by human curiosity, the effect of the gravitational bending of light has evolved on unforeseen paths, in an interplay between shifts in prevailing paradigms and advance of technology, into the most unusual way to study planet populations. The confirmation of the bending angle predicted by Einstein with the Solar Eclipse measurements from 1919 marked the breakthrough of the theory of General Relativity, but it was not before the detection of the double image of the quasar 0957+561 that ‘gravitational lensing’ really entered the observational era. The observation of a characteristic transient brightening of a star caused by the gravitational deflection of its light by an intervening foreground star, constituting a ‘microlensing event’, required even further advance in technology before it could first emerge in 1993. While it required more patience in waiting before ‘Einstein’s blip’ for the first time revealed the presence of a planet orbiting a star other than the Sun, such detections can now be monitored live, and gravitational microlensing is not only sensitive to masses as low as that of the Moon, but can even reveal planets around stars in galaxies other than the Milky Way.     

Newtonian forms for the motion of particles and photons in dilaton spacetime

Using Newtonian forms for equations of motion, we consider the motion of particles and photons in the dilaton spacetime. Some classical gravitational effects, such as the bending of light rays, the perihelion advance of a planet, the delay of radar echo, and the gravitational redshifts, have been investigated. The results show that the gravitational effects arising from the dilaton can be observed provided that the dilaton is large enough.     

Rebounce and black hole formation in a gravitational collapse model with vanishing radial pressure

We examine here spherical gravitational collapse of a matter model with vanishing radial pressure and non-zero tangential pressure. It is seen analytically that the collapsing cloud either forms a black hole or disperses depending on values of the initial parameters which are initial density, tangential pressure and velocity profile of the cloud. A threshold of black hole formation is observed near which a scaling relation is obtained for the mass of black hole, assuming initial profiles to be smooth. The similarities in the behaviour of this model at the onset of black hole formation with that of numerical critical behaviour in other collapse models are indicated.     

Multilayer ring structures

A study of the behavior of axisymmetric structures is important for understanding the problem of the existence and stability of planet rings, spherical star constellations, and galaxies. The multilayer ring structure algorithm is developed on the basis of an exact solution to the problem of n-body gravitational axisymmetric interaction. As a result of the numerical integration of differential motion equations of point bodies composing the above structures, the evolution of several of their models is investigated. Some of them are invariable in configuration, others change forms due to interlayer interactions, and the rest throw part of bodies out of the structure.     

On quantum iterated function systems

A Quantum Iterated Function System on a complex projective space is defined through a family of linear operators on a complex Hilbert space. The operators define both the maps and their probabilities by one algebraic formula. Examples with conformal maps (relativistic boosts) on the Bloch sphere are discussed.     

Disks around young stellar objects

By 1939, when Chandrasekhar’s classic monograph on the theory of Stellar Structure was published, although the need for recent star formation was fully acknowledged, no one had yet recognized an object that could be called a star in the process of being born. Young stellar objects (YSOs), as pre-main-sequence stars, were discovered in the 1940s and 1950s. Infrared excess emission and intrinsic polarization observed in these objects in the 1960s and 1970s indicated that they are surrounded by flattened disks. The YSO disks were seen in direct imaging only in the 1980s. Since then, high-resolution optical imaging with HST, near-infrared adaptive optics on large ground-based telescopes, mm and radiowave interferometry have been used to image disks around a large number of YSOs revealing disk structure with ever-increasing detail and variety. The disks around YSOs are believed to be the sites of planet formation and a few such associations have now been confirmed. The observed properties of the disk structure and their evolution, that have very important consequences for the theory of star and planet formation, are discussed.     

Core-collapse supernovae: Magnetorotational explosions and jet formation

Core-collapse supernovae are accompanied by formation of neutron stars. The gravitational energy is transformed into the energy of the explosion, observed as SN II, SN Ib,c type supernovae. We present results of 2D MHD simulations, where the source of energy is rotation and the magnetic field serves as a “transition belt” for the transformation of the rotation energy into the energy of the explosion. The toroidal part of the magnetic energy initially grows linearly with time due to differential rotation. When the twisted toroidal component strongly exceeds the poloidal field, magneto-rotational instability develops, leading to a drastic acceleration in the growth of magnetic energy. Finally, a fast MHD shock is formed, producing a supernova explosion. A mildly collimated jet is produced for the dipolelike type of the initial field. The text was submitted by the authors in English.