共查询到20条相似文献，搜索用时 31 毫秒
1.
The polarization-correction energy-momentum tensor for a semi-classical gravitational theory is derived. This tensor accounts for the creation of particles from a vacuum at a finite temperature. The theory contains an asymptotic cosmological Friedmann solution. The solution obtained turns out to be dynamically stable, so that it can form the observed properties of the Universe. New cosmological solutions describing the early stages of cosmological evolution of a homogeneous isotropic Universe are obtained. One of these corresponds to the simultaneous creation of matter and geometry from the vacuum of a flat, empty space-time without structure. Another solution corresponds to a high-temperature inflation regime. A cosmological scenario for the creation of the observed Universe from “nothing” that includes the properties of all the solutions obtained is put forward. 相似文献
2.
D. D. Sokoloff 《Astronomy Reports》2003,47(12):975-978
A cosmological scenario in which the topology of the Universe is treated like a dynamical time-dependent variable is put forward. The Universe could be small in an initial quantum stage of evolution and then gradually increase its dimensions so that the present-day nontrivial topology is manifest only far beyond the cosmological horizon. 相似文献
3.
V. V. Burdyuzha 《Astronomy Reports》2009,53(5):381-388
We briefly discuss a modern view of the cosmological constant. It is suggested that the cosmological constant was “hardened” at E ～ 150 MeV after the latest (quark-gluon) phase transition. Until this energy was reached, the vacuum component of the Universe evolved (decreased) in a series of discontinuous jumps; i.e., condensates of quantum fields made negative contributions to its positive energy density. This was the quintessence period of the evolution of the Universe, when it underwent an intense loss of symmetry during the first fractions of a microsecond of its existence. However, this point of view is not without criticism, and other approaches are considered. In particular, the small value of the cosmological constant and its ability to accelerate the expansion of the Universe is of great interest. Although all available data on the cosmological constant were recently summarized and classified by S. Nobbenhuis, no satisfactory solution to this problemhas been reached, and this represents a major difficulty for progress in quantum-gravity theory and cosmology. We briefly discuss the possibility for stars to be formed from dark energy (vacuum stars) and the extension of holographic ideas to the entire Universe. We also consider the possibility of solving the problem of the cosmological constant by introducing a universal wave function; i.e., quantum decoherence, which implies the rejection of the Copenhagen interpretation of quantum mechanics and the acceptance of H. Everett’s point of view. 相似文献
4.
It is shown that inclusion of the shear stresses to the cosmological evolution can stabilize the Friedmann Big Bang. This results in the existence of the generic solution with isotropic cosmological singularity. 相似文献
5.
We briefly review the history of the cosmological constant. Recently discovered accelerated expansion epoch of the universe placed the problem of the cosmological constant at a forefront of interest of astronomers and physicists. Short account of recent developments is given. 相似文献
6.
The results of several cosmographic tests of the standard ΛCDM model taking into account evolution and a “tired-light” model without evolution are compared. Physical tests and observations of the microwave background are also considered. Arguments supporting each of these models are presented. The general conclusion is that it is not possible to unambiguously identify a preferred cosmological model based on the currently available observational data. The nature of the redshift of spectral lines emitted by extragalactic objects is discussed. Possibilities for further studies are also briefly noted. 相似文献
7.
It is known that ΛCDM cosmological models predict too many dark halos compared to the observed numbers. This excess is derived from the virialized mass in the Local Supercluster and its vicinity. Taking into account cosmological velocity fluctuations during the formation of the dark halo population makes it possible to eliminate this remaining contradiction in the ΛCDM model. Based on Press-Schechter formalism, a model describing the formation of the dark halo population is developed, taking into account kinematic effects in the dark matter. A quantitative explanation of the virialized-mass deficit in the local Universe is obtained in this model. 相似文献
8.
Astronomy Reports - It has recently become clear that the potential role of astrometry in cosmological studies has been underestimated. Some areas of cosmology that should be investigated using... 相似文献
9.
A Scheme of the Hierarchy for Sequence Stratigraphy 总被引：15，自引：0，他引：15
Inthelasttwodecades,sequenCestratigraphyhasbecomethecornerstoneofmodernstratigraphyandhasbeenwidelyusedbothintheexplorationofoilandgasandinthestudyofregionalgeology.Assequencestratigraphyhasextendedfromundergroundinvestigationsbyseismicmethodstooutcropstudiesbyordinary$tratigraphicapproaches,andasithasgrownintoamoreorlessmaturebranchofstratigraphicaldisciplines,theestablishmentofarelevanthierarchyofthesequencestratigraphictntSseemstohavebecomeoneoftheurgefltrequire~,especiallyasthereexistsomec… 相似文献
10.
Astronomy Reports - The review considers the contribution of the results of measuring fluctuations of relic cosmic microwave background (CMB) radiation to cosmological model and the latest results... 相似文献
11.
E. P. Kurbatov 《Astronomy Reports》2014,58(6):386-398
A modification of the Press-Schechter model for the mass function of the dark halos, whose population develops in the presence of a supercluster or a cosmological void, is proposed. The large-scale structure is specified as a set of statistical constraints in the form of linear functionals that are applied to the initial overdensity field. The parameters and values of these functionals are related to properties of the large-scale structure: its mean density, spatial scales, and shape. The model is applied to the simple case of a spherically symmetric background structure to demonstrate a procedure for recovering these parameters by fitting the halo mass function. 相似文献
12.
P. A. Nakaznoy 《Astronomy Reports》2010,54(2):121-125
The rotation curves of spiral galaxies are modeled in the case when the cosmological term depends linearly on the Ricci scalar.
Themodel galaxy is approximated using a thin disk with an exponential radial distribution of the matter density. This model
is used to estimate the free parameter of the theory, and to construct model rotation curves for several selected galaxies.
The results obtained are in satisfactory agreement with observations. 相似文献
13.
A model of a star consisting of vacuum-like matter is constructed in the framework of general relativity. Its stability and other physical properties are analyzed. This stellar model is compared with cosmological models consisting of the same vacuum-likematter with a pressure equal to the energy density but with the opposite sign.
相似文献14.
The development of Zeldovich’s ideas on the cosmological impact of particle theory is discussed in the context of cosmoparticle physics, studying fundamental relationship of macro- and micro-worlds. 相似文献
15.
M. S. Burgin 《Astronomy Reports》2003,47(9):709-716
The balance equations for the quasi-stationary recombination of hydrogen plasma in a black-body radiation field are solved. The deviations of the excited level populations from equilibrium are computed and the rates of uncompensated line transitions determined. The expressions obtained are stable for computations of arbitrarily small deviations from equilibrium. The average number of photons emitted in hydrogen lines per irreversible recombination is computed for plasma parameters corresponding to the epoch of cosmological recombination. 相似文献
16.
L. M. Chechin 《Astronomy Reports》2016,60(6):535-541
A step-by-step foundation for the differential character of the Universe’s rotation is presented. First, invoking the concept of spacetime foam with spin, it is reasonable to assume that the very early Universe can be described by the Dirac equation. Second, it is shown using the Ehrenfest theorem that, from a classical point of view, the early Universe can be described by the Papapetrou equations. Third, it is stressed that our Universe can perform only rotational motion. It is shown based on the spin part of the Papapetrou equations that the Universe’s rotation depends appreciably on the physical properties of a specific cosmological epoch. The rotational angular velocity is calculated for three basic cosmological epochs: the matter-dominated epoch, the transition period (from domination of matter to domination of vacuum), and the vacuum-dominated epoch. 相似文献
17.
Data on the dependences of the masses and bolometric luminosities of Active Galactic Nuclei on their cosmological redshifts are used to determine the redshift dependences of their X-ray luminosities and the kinetic powers of their relativistic jets. These results are used, in turn, to obtain the redshift dependence of the spins of the central supermassive black holes. 相似文献
18.
Using a sample of radio sources observed with Very Long Baseline Interferometry (VLBI) and the standard cosmological model,
it is shown that the cores of radio sources observed with ground-based VLBI with resolutions of the order of several milliarcseconds
(which serve as ultra-compact radio sources) cannot be used as “standard rulers“ in the angular size-redshift cosmological
test. This is a consequence of the insufficient resolution of ground-based VLBI arrays and the flux-limited nature of the
radio samples used. In this case, the luminosity-linear size correlation detected in many studies of VLBI source samples has
an instrumental origin, in contrast to the analogous correlation for radio galaxies and quasars on angular scales of several
arcseconds. 相似文献
19.
The role of pressure as a source of gravity in general relativity is considered. In homogeneous, anisotropic cosmological models, the anisotropic pressure components along different coordinate axes are included as terms in the equations determining the accelerations along these axes; in this sense, this situation is similar to how the mass density is included in these equations. A change in the pressure component along one of the coordinates leads to an anisotropic change in the accelerations along all three coordinates. However, the pressure components are not present in the equation determining the initial conditions. On the other hand, with an inhomogeneous matter density distribution, the mass density and pressure play fundamentally different roles as sources of gravity. The consequences of this are considered. 相似文献
20.
Astronomy Reports - The modern Standard cosmological scenario, reflecting to large extent the development of Zeldovich’s legacy in cosmoparticle physics, involves inflation, baryosynthesis... 相似文献