共查询到20条相似文献，搜索用时 656 毫秒
1.
In the present work we assume that the universe is dominated with a two component mixture which do not evolve separately but interact non-gravitationally with one another. we consider the issue of the tachyon as a source of the dark energy and modified Chaplygin gas as background fluid. So we study the interacting between tachyon field and modified Chaplygin gas in different forms of interactions term Q in both flat and non-flat FRW universe. Then we reconstruct the potential and the dynamics of the tachyon field which describe tachyon cosmology. Also we find a equivalence potential for MCG in this model. Next we study two dark components respect to redshift and we find the conditions that are required for the stability of this model. 相似文献
2.
Manuele Santoprete 《Celestial Mechanics and Dynamical Astronomy》2006,94(1):17-35
In this paper, we study the linear stability of the relative equilibria for homogeneous and quasihomogeneous potentials. First,
in the case the potential is a homogeneous function of degree −a, we find that any relative equilibrium of the n-body problem with a>2 is spectrally unstable. We also find a similar condition in the quasihomogeneous case. Then we consider the case of three
bodies and we study the stability of the equilateral triangle relative equilibria. In the case of homogeneous potentials we
recover the classical result obtained by Routh in a simpler way. In the case of quasihomogeneous potentials we find a generalization
of Routh inequality and we show that, for certain values of the masses, the stability of the relative equilibria depends on
the size of the configuration. 相似文献
3.
本文讨论的是中子星自洽的有限磁层大气模型,先用试探解方法得到一个解析解,它给出有限磁层大气的分布轮廓,然后用能量最小原理讨论了其特性,取得了有意义的结果。同时,通过对其等离子体与真空交界面的研究,得出其交界面也是稳定的。最后,我们对模型的发展作了展望,指出赤道区的超共转,可能与子脉冲漂移有关,从这个模型出发,我们将可能最终建立一个自洽的有辐射的模型。 相似文献
4.
Li Yuan-jie 《Chinese Astronomy and Astrophysics》1984,8(4):277-282
It is pointed out that, when calculating the angular momentum of a Kerr black hole, we should allow for the effect of accretion of scattered electrons in the retrograde direction. By using the radius of smallest circular orbit of the particle as a measure for the capture cross-section by the hole, the calculation is greatly simplified. Thorne's result, a/M = 0.9982, when retrograde photons are considered, is easily obtained. If we allow for retrograde electrons, we get a/M = 0.9986, if we allow for both retrograde electrons and photons, we get a/M = 0.9968; and if we further allow for pair annihilation, we get a/M = 0.9961. 相似文献
5.
Tadeusz Jan Jopek Christiane Froeschlé Robert Gonczi Piotr A. Dybczyński 《Earth, Moon, and Planets》2008,102(1-4):53-58
We present the results of an extensive study of the Tunguska Cosmic Body (TCB) origin on dynamical grounds. To identify the
TCB parent, or a plausible candidate, we applied the well-known concept of dynamical similarity whereby we have compared the
geocentric and heliocentric dynamical parameters of a selected set of the Near Earth Objects (NEOs) and TCB particles. First,
we made use the idea of Kresak by comparing geocentric coordinates of the TCB radiant with those of the NEOs. Second, we studied
the long-term dynamical evolution of all NEOs and TCB particles searching for similarities between their heliocentric orbits.
As a general result, we observed many more similar cases and a different pattern of the high orbital similarity among the
TCB particles and the asteroid orbits than we did for comets. 相似文献
6.
Eric J. Bakker 《Astrophysics and Space Science》1997,251(1-2):73-80
In this paper we discuss the relevance, and possible scientific gains, which can be acquired from studying circumstellar molecular spectra toward evolved stars. Where can we expect circumstellar molecular spectra, why would we want to study these spectra, which molecules might be present, and what can we learn from these studies? We present an overview of reported detections, and discuss some of the results. 相似文献
7.
In the three dipole problem where enormous electromagnetic forces obstruct the three dimensional movement of the charged particle we determined for the first time families of three dimensional asymmetric periodic orbits. We study how these families appear, branching from the planar motion and we develop the procedures we have followed to determine them numerically. Also we give their characteristics and the conical projections and plottings of some orbits. 相似文献
8.
About 20 years after the discovery of the first extrasolar planet, the number of planets known has grown by three orders of magnitude, and continues to increase at neck breaking pace. For most of these planets we have little information, except for the fact that they exist and possess an address in our Galaxy. For about one third of them, we know how much they weigh, their size and their orbital parameters. For less than 20, we start to have some clues about their atmospheric temperature and composition. How do we make progress from here?We are still far from the completion of a hypothetical Hertzsprung–Russell diagram for planets comparable to what we have for stars, and today we do not even know whether such classification will ever be possible or even meaningful for planetary objects. But one thing is clear: planetary parameters such as mass, radius and temperature alone do not explain the diversity revealed by current observations. The chemical composition of these planets is needed to trace back their formation history and evolution, as happened for the planets in our Solar System. As in situ measurements are and will remain off-limits for exoplanets, to study their chemical composition we will have to rely on remote sensing spectroscopic observations of their gaseous envelopes.In this paper, we critically review the key achievements accomplished in the study of exoplanet atmospheres in the past ten years. We discuss possible hurdles and the way to overcome those. Finally, we review the prospects for the future. The knowledge and the experience gained with the planets in our solar system will guide our journey among those faraway worlds. 相似文献
9.
In this letter, we have considered that the universe is filled with normal matter and variable modified Chaplygin gas. Also we have considered the interaction between normal matter and variable modified Chaplygin gas in FRW universe. Then we have considered a correspondence between the holographic dark energy density and interacting variable modified Chaplygin gas energy density. Then we have reconstructed the potential of the scalar field which describes the variable modified Chaplygin cosmology. 相似文献
10.
《New Astronomy》2022
In this paper, we study the weak deflection angle in the spacetime of improved Schwarzschild black hole using the method derived by Gibbons and Werner. To do so, we derive the optical curvature from the optical metric and calculate deflection angle in weak field limits by using the Gauss–Bonnet theorem. Moreover, we study the effect of the plasma medium on the weak gravitational lensing using the Gauss–Bonnet theorem. Furthermore, we also study the graphical analysis of the deflection angle in both the plasma and non-plasma mediums. Moreover, we obtain the bound on greybody for improved Schwarzschild black hole. 相似文献
11.
We first recall the observations concerning the opaque rings of Saturn and Uranus. Then we describe a model which represents the kinematics of these rings. Finally we review how we treat collisions, self-gravity and satellite perturbations and what are the basic effects of these forces. 相似文献
12.
V. Delouille J. De Patoul J. F. Hochedez L. Jacques J. P. Antoine 《Solar physics》2005,228(1-2):301-321
The extreme ultraviolet imaging telescope (EIT) of SOHO offers a unique record of the solar atmosphere for its sampling in
temperature, field of view, resolution, duration, and cadence. To investigate globally and locally its topology and evolution
during the solar cycle, we consider a multi-scale approach, and more precisely we use the wavelet spectrum.
We present three results among the applications of such a procedure. First, we estimate the typical dimension of the supergranules
as seen in the 30.4 nm passband, and we show that the evolution of the characteristic network scale is almost in phase with
the solar cycle. Second, we build pertinent time series that give the evolution of the signal energy present in the corona
at different scales. We propose a method that detects eruptions and post-flaring activity in EUV image sequences. Third, we
introduce a new way to extract active regions in EIT images, with perspectives in, e.g., long-term irradiance analysis. 相似文献
13.
Jayadev Rajagopal G. Srinivasan K. S. Dwarakanath 《Journal of Astrophysics and Astronomy》1998,19(3-4):117-131
In the preceding paper (Paper I), we presented HI absorption spectra towards radio sources very close to the lines of sight
towards twenty five bright stars against which optical absorption spectra had been obtained earlier, In this paper we analyse
the results and draw some conclusions.
To summarize briefly, in most cases we found HI absorption at velocities corresponding to the optical absorption features
provided one restricted oneself to velocities ≲10 kms-1. At higher velocities we did not detect any HI absorption down to
an optical depth limit of 0.1 (except in four cases which we attribute to gas in systematic motion rather than clouds in random
motion). After discussing various scenarios, we suggest that this trend should perhaps be understood in terms of the high
velocity interstellar clouds being accelerated, heated and ablated by expanding supernova remnants. 相似文献
14.
《天文和天体物理学研究(英文版)》2021,(8)
By means of identical cubic elements, we generate a partition of a volume in which a particle-based cosmological simulation is carried out. In each cubic element, we determine the gas particles with a normalized density greater than an arbitrarily chosen density threshold. By using a proximity parameter, we calculate the neighboring cubic elements and generate a list of neighbors. By imposing dynamic conditions on the gas particles, we identify gas clumps and their neighbors, so that we calculate and fit some properties of the groups so identified, including the mass, size and velocity dispersion, in terms of their multiplicity(here defined simply as the number of member galaxies). Finally, we report the value of the ratio of kinetic energy to gravitational energy of such dense gas clumps, which will be useful as initial conditions in simulations of gravitational collapse of gas clouds and clusters of gas clouds. 相似文献
15.
Xi-Yun Hou 《中国天文和天体物理学报》2009,9(4)
In a previous paper, we proposed another special critical value concerning the evolution of the long period family around the equilateral equilibrium points, besides the two values given by Henrard. Are there any other special critical values? After studying the stability curves of the long period family carefully, we gave a negative answer. During the study, we found an interesting family of periodic orbits which we called the homo family. We studied the evolution of this family following the increase of μ. With these findings, we were able to explain the origin of the four branches of periodic families emanating from L4 and the stability results of the equilateral equilibrium points. 相似文献
16.
This paper is the first of a set of four, in which we shall develop the first part of a project dedicated to elaborating a Hamiltonian theory for the rotational motion of a deformable Earth. Here we study only the perturbation due to the deformation of the elastic mantle by tidal body force. In the present paper, we define two canonical systems of variables—we give these variables the names of elastic variables of Euler and Andoyer respectively. Next, using them, we obtain the canonical expression of rotational kinetic energy, which is valid for any Earth model satisfying hypotheses as general as those established in Section 2. 相似文献
17.
Mapping Mercury's internal magnetic field with a magnetometer in closed orbit around the planet will provide valuable information about its internal structure. By measuring magnetic field multipoles of order higher than the dipole we could, in principle, determine some properties, such as size and location, of the internal source. Here we try to quantify these expectations. Using conceptual models, we simulate the actual measurement during the BepiColombo mission, and then we analyze the simulated data in order to estimate the measurement errors due to the limited spatial sampling. We also investigate our ability to locate the field generating current system within the planet. Finally, we address the main limitation of our model, due to the presence of time-varying external magnetospheric currents. 相似文献
18.
In this paper, we investigate Bianchi type-VI cosmological model for the universe filled with dark energy and viscous fluid in the presence of cosmological constant. Also, we show accelerating expansion of the universe by drawing volume scale, pressure and energy density versus cosmic time. In order to solve the Einstein’s field equations, we assume the expansion scalar is proportional to a component of the shear tensor. Therefore, we obtain the directional scale factors and show the EOS parameter crosses over phantom divided-line. 相似文献
19.
We consider the Sitnikov problem; from the equations of motion we derive the approximate Hamiltonian flow. Then, we introduce
suitable action–angle variables in order to construct a high order normal form of the Hamiltonian. We introduce Birkhoff Cartesian
coordinates near the elliptic orbit and we analyze the behavior of the remainder of the normal form. Finally, we derive a
kind of local stability estimate in the vicinity of the periodic orbit for exponentially long times using the normal form
up to 40th order in Cartesian coordinates. 相似文献
20.
Studying the general kinetic behaviour of a charged particle in the space of three celestial bodies electromagnetic field we give here for the first time the equilibrium configurations of the dynamical system with all the variational equations and integrals. Also we develop the procedure we follow for locating the planar and the three-dimensional equilibrium points demonstrating an extensive numerical investigation of them by giving their number under the influence of the variation of the magnetic field and in all the cases we list their coordinates and energy. 相似文献