共查询到20条相似文献,搜索用时 31 毫秒
1.
Corrado Massa 《Astrophysics and Space Science》2008,314(1-3):23-24
If gravity is a mixture of the ordinary attractive force carried by the massless graviton, and of a repulsive force carried
by a particle with nonzero mass, an evaporating black hole might leave a stable remnant. 相似文献
2.
Song Guo-xuan Yan Hao-jian Xu Tong-qi Zhu Shi-chang 《Chinese Astronomy and Astrophysics》1981,5(3):332-336
We have found an interior solution of the Einstein equation containing a vector graviton field under a special mass distribution. 相似文献
3.
A. R. El-Nabulsi 《Astrophysics and Space Science》2010,325(2):277-281
In this work, we explore many cosmological implications of a four-dimensional cosmology dominated by quintessence with a static
traversable wormhole, spatio-temporal varying G and by taking into account a decaying cosmological constant and a decaying graviton mass by means of an additional bimetric
tensor in Einstein’s field equations proposed by Visser in 1998. 相似文献
4.
R. A. Burenin 《Astronomy Letters》2013,39(6):357-366
The constraints on total neutrino mass and effective number of neutrino species based on CMB anisotropy power spectrum, Hubble constant, baryon acoustic oscillations and galaxy cluster mass function data are presented. It is shown that discrepancies between various cosmological data in Hubble constant and density fluctuation amplitude, measured in standard ΛCDM cosmological model, can be eliminated if more than standard effective number of neutrino species and non-zero total neutrino mass are considered. This extension of ΛCDM model appears to be ≈3σ significant when all cosmological data are used. The model with approximately one additional neutrino type, N eff ≈ 4, and with non-zero total neutrino mass, Σmν ≈ 0.5 eV, provide the best fit to the data. In the model with only one massive neutrino the upper limits on neutrino mass are slightly relaxed. It is shown that these deviations from ΛCDM model appearmainly due to the usage of recent data on the observations of baryon acoustic oscillations. The larger than standard number of neutrino species is measured mainly due to the comparison of the BAO data with direct measurements of Hubble constant, which was already noticed earlier. As it is shown below, the data on galaxy cluster mass function in this case give the measurement of non-zero neutrino mass. 相似文献
5.
Chen Fu-sheng 《Chinese Astronomy and Astrophysics》1984,8(4):286-289
The surface temperature of a rotating, charged body is found separately under the Kerr-Newman metric and the vector graviton metric. Particular reference is made to pulsars. It is found that, 1) under the Kerr-Newman metric, the surface temperature rises from the poles to the equator, when the radius R of the body is greater than a certain critical value, rn. When R= rn, the surface temperature is uniform. When R < rn, the above gradient is reversed. For pulsars, the equatorial temperature is some 3 × 104 K higher than the polar temperature. 2) Under the Vector graviton field metric, a similar temperature differential exists, but it is much smaller in size. 相似文献
6.
General relativistic electrodynamics in a torsion background can give rise to a situation where the photons can ahve a non-zero rest mass and magnetic moment. Astrophysical limits are used to constrain these parameters. 相似文献
7.
Michael J. Clark 《Astrophysics and Space Science》2018,363(10):217
A theoretical basis for modifying Newtonian dynamics on a galactic scale can be obtained by postulating that cosmic rays interact with graviton exchanges between distant masses. This assumes that these charged particles move under the influence of local electromagnetic fields rather than the weak gravitational fields of distant matter. It leads to an enhancement of graviton exchanges between distant masses via an additional gravitational force term inversely proportional to distance. At planetary and local interstellar distances this predicts an extremely small additional gravitational force, but it can become significant on a galactic scale. The model is used here to predict rotational velocities in a wide range of galaxies including the Milky Way, Andromeda (M31) and some galaxies in the THINGS study. Results are obtained assuming a galactic cosmic ray density consistent with observations in the solar system. This approach is compared with the dark matter hypothesis and with Modified Newtonian Dynamics (MOND), the two primary postulates used to explain the constant rotational velocities observed in most galaxies. 相似文献
8.
This paper discusses the effect of neutrinos with non-zero rest-mass on the clustering process in the early universe. The early universe is regarded as a two-component fluid, one component being the de-coupled neutrinos, and the other being matter and radiation, between the two there is only the gravitational coupling. The main conclusions are: (1) such neutrinos will cause clustering of matter before the epoch of re-combination; (2) the mass so clustered will be in the range of the mass of clusters of galaxies; (3) there exists a preferential clustering scale, corresponding to the earliest onset of Jeans instability; (4) if the rest-mass is below a certain value, then there will be no effect. 相似文献
9.
This paper aims to explore anisotropic planar analytical models for dissipative as well as non-dissipative matter distributions. We relate the Weyl tensor and physical variables of matter distribution. Darmois junction conditions are formulated on internal and external hypersurfaces. It is found that our dissipative models show the presence of cavity with non-zero expansion. Finally, we investigate two types of solutions with zero shear as well as heat flux by a specific choice of the mass function and by restricting pressure. 相似文献
10.
In this paper, we investigate the influence of the massive neutrino on the early evolution of adiabatic perturbations in the Universe. It is shown that if the neutrino has a non-zero rest mass, the perturbations that are approximately in a critical, stable state (for the Jeans instability) before the recombination of hydrogen will possibly grow into a kind of astronomical object which will have a preferred scale after the recombination. A reasonable estimate of the order of magnitude shows that such objects seem to be corresponding to the observed galaxies. 相似文献
11.
R. I. Hynes K. O'' Brien F. Mullally T. Ashcraft 《Monthly notices of the Royal Astronomical Society》2009,399(1):281-286
Caustics are a generic feature of the non-linear growth of structure in the dark matter distribution. If the dark matter were absolutely cold, its mass density would diverge at caustics, and the integrated annihilation probability would also diverge for individual particles participating in them. For realistic dark matter candidates, this behaviour is regularized by small but non-zero initial thermal velocities. We present a mathematical treatment of evolution from hot, warm or cold dark matter initial conditions which can be directly implemented in cosmological N -body codes. It allows the identification of caustics and the estimation of their annihilation radiation in fully general simulations of structure formation. 相似文献
12.
Peter W. Blum 《Planetary and Space Science》1974,22(1):183-186
An approximation for the height distribution of nitrogen and atomic oxygen in the thermosphere between 120 and 500 km is obtained by the assumption that these constituents are in diffusive equilibrium. The horizontal wind system in the thermosphere may cause deviations from the diffusive equilibrium distribution due to the non-zero divergence of the horizontal flow and the vertical mass motion associated with it. Stubbe has examined this problem and deduced considerable deviations from diffusive equilibrium due to this effect. The problem is re-examined here, and it is shown that there exist arguments that the deviations from diffusive equilibrium due to horizontal wind fields are not as large as suggested by Stubbe. 相似文献
13.
C. Sivaram 《Astrophysics and Space Science》1985,116(1):39-42
Recently it was pointed out that a non-zero cosmological constant can play a role in the formation of neutrino halos only in the case of neutrinos of very low rest mass (m
v
<-0.1eV). However, phase-space considerations would requirem
v
>50 eV if neutrinos dominate the missing mass in halos of large spiral galaxies and moreoverm
v
>200 eV is implied in the case of dwarf spheroidals. These larger neutrino masses would be in conflict with observed constraints on the age of the Universe unless a cosmological constant is invoked. 相似文献
14.
A. T. Sinclair 《Celestial Mechanics and Dynamical Astronomy》1970,2(3):350-350
Various families of periodic solutions are shown to exist in the three body problem, in which two of the bodies are close to a commensurability in mean motions about the third body, the primary, which is considerably more massive than the other two. The cases considered are
- The non-planar circular restricted problem (in which one of the secondary bodies has zero mass, and the other moves in a fixed circular orbit about the primary).
- The planar non-restricted problem (in which the three bodies move in a plane, and both secondaries have finite mass).
- The planar elliptical restricted problem (in which the three bodies move in a plane, one of the secondary bodies has zero mass, and the other moves in a fixed elliptical orbit about the primary).
15.
We develop a quantitative criterion for the collapse of matter within a region where a global texture just collapsed and a non-zero peculiar velocity field is produced. We also describe the evolution of the density contrast in this region according to the non-linear spherical collapse model. In particular, we find that the overdensity needed to virialisation is reached at z ≤ 2.2, covering a mass range of about 104–107 M⊙ in the context of an Einstein-de Sitter universe. 相似文献
16.
We consider the non-axisymmetric, dynamical instability of a thin accretion torus with a non-zero shift of corotation radius. By numerical method we evaluated the wave number dependence of the linear rate of growth of instability and the co-rotation shift. The rate of growth is only slightly affected by the non-zero co-rotation shift, while the dispersion relation in the case of a shift is the same as that of the linear KdV equation. This shows that the “planet-like” solution found in numerical simulations of thin tori is very probably analogous to the soliton solution of the KdV equation. 相似文献
17.
The photometric solutions of W UMa-type binary BW Dra have been determined by applying the Wilson and Devinney Code toUBV observations of Rucinski and Kaluzny.It is shown that BW Dra is corresponding to a system with an overcontact configuration and smaller mass ratioq=0.392 andUBV light curves give the converging solutions with non-zero third light.It is proved that the components of BW Dra are older stars (the spectral types are G0 and G3, respectively). They could come into contact later stage of evolution. The photometric solution is similar to the results of Kaluzny and Rucinski. According to the photometric solution and spectroscopic results of Batten and Lu, the absolute parameters are presented too. 相似文献
18.
The dynamical evolution of triple systems with equal and unequal-mass components and different initial velocities is studied. It is shown that, in general, the statistical results for the planar and three-dimensional triple systems do not differ significantly. Most (about 85%) of the systems disrupt; the escape of one component occurs after a triple approach of the components. In a system with unequal masses, the escaping body usually has the smallest mass. A small fraction (about 15%) of stable or long-lived systems is formed if the angular momentum is non-zero. Averages, distributions and coefficients of correlations of evolutionary characteristics are presented: the life-time, angular momentum, numbers of wide and close triple approaches of bodies, relative energy of escapers, minimum perimeter during the last triple approach resulting in escape, elements of orbits of the final binary and escaper. 相似文献
19.
C. Lozanovski 《Astrophysics and Space Science》2014,351(1):371-376
A class of purely magnetic diagonal Bianchi type VI h Cosmologies is investigated. If the energy-momentum tensor is specialized to that of a perfect fluid with (non-zero) heat-flux, with respect to the co-moving fluid 4-velocity, then the only solution is of Bianchi type V and un-physical. Further, it is shown that if certain metric functions are functionally related then the spacetime is conformally flat. Unfortunately, all these results (somewhat indirectly) invalidate a claim by Kumar and Srivastava of finding a non-conformally flat purely magnetic diagonal Bianchi type V cosmology. Finally, we consider non-zero anisotropic pressure in place of non-zero heat flux. It is shown that these spacetimes are necessarily Bianchi type VI 0. We highlight the fact that there is a known solution that generalizes the purely magnetic perfect fluid Wylleman-Van den Bergh spacetime. Physical properties of this solution are discussed. 相似文献
20.
《Chinese Astronomy and Astrophysics》1982,6(2):163-167
In the light of the experiments /3,4/ showing that neutrinos may have a non-zero rest-mass, we discuss the constraints placed on the cosmological term Λ and the Hubble constant Ho by such a mass and the age of the universe in the Lemaitre model. An upper limit of Λ of 15 × 10?57/cm2 and possible ranges of Ho are given. 相似文献