共查询到20条相似文献，搜索用时 140 毫秒
1.
D. L. Khokhlov 《Astrophysics and Space Science》2011,335(2):577-580
The Einstein static model of the universe as a whole is considered. The Hubble law is explained by the Doppler effect due
to the downward inertial acceleration along a certain radius experienced by an observer in the center of the universe, with
the total acceleration over all radii being equal zero. Evolution of the universe is introduced through the wave function
of the universe dependent on time. This yields the energy density of the universe hence the temperature of the universe dependent
on time. On the contrary, the energy, forth and intensity of radiation are fixed with time that allows to develop the Newtonian
physics in the whole universe. The time-temperature relation of the universe in the model considered is the same as in the
radiation dominated universe in the Friedmann model that allows to explain primordial nucleosynthesis as it is in the standard
scenario. The modern parameters of the universe in the model considered are consistent with the observations. 相似文献
2.
T. X. Zhang 《Astrophysics and Space Science》2010,330(1):157-165
Modifying slightly the big bang theory, the author has recently developed a new cosmological model called black hole universe.
This new cosmological model is consistent with the Mach principle, Einsteinian general theory of relativity, and observations
of the universe. The origin, structure, evolution, and expansion of the black hole universe have been presented in the recent
sequence of American Astronomical Society (AAS) meetings and published recently in a scientific journal: Progress in Physics.
This paper explains the observed 2.725 K cosmic microwave background radiation of the black hole universe, which grew from
a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present
universe with hundred billion-trillions of solar masses. According to the black hole universe model, the observed cosmic microwave
background radiation can be explained as the black body radiation of the black hole universe, which can be considered as an
ideal black body. When a hot and dense star-like black hole accretes its ambient materials and merges with other black holes,
it expands and cools down. A governing equation that expresses the possible thermal history of the black hole universe is
derived from the Planck law of black body radiation and radiation energy conservation. The result obtained by solving the
governing equation indicates that the radiation temperature of the present universe can be ∼2.725 K if the universe originated
from a hot star-like black hole, and is therefore consistent with the observation of the cosmic microwave background radiation.
A smaller or younger black hole universe usually cools down faster. The characteristics of the original star-like or supermassive
black hole are not critical to the physical properties of the black hole universe at present, because matter and radiation
are mainly from the outside space, i.e., the mother universe. 相似文献
3.
A. Dinculescu 《Astrophysics and Space Science》2009,321(2):123-126
The objective of this paper is to draw attention to the close similarity between the observable universe and the photon mean
free path sphere. It is hoped that by analyzing in depth this apparent connection one will be able to explain why our present
epoch appears to have special properties. It is shown that some theoretical arguments point to an equality between the number
of particles in the observable universe and the number of particles in the largest self-gravitating photon mean free path
sphere (MxPhMFPS.) This equality, supported by observational data, leads to a series of equations that relate in simple manner characteristics
of the observable universe with characteristics of the MxPhMFPS, and allows a more precise approximation of the values of the main cosmological parameters. It is also shown that by replacing
the protons in the MxPhMFPS with positrons, the radiation resulted by their interaction with the existing electrons has an energy equal to the energy
of the electromagnetic radiation in the observable universe. 相似文献
4.
A. Bhadra 《Astrophysics and Space Science》2007,310(1-2):169-172
Scalar tensor (ST) theories of gravitation contain an attractor mechanism towards general relativity. The mechanism is supposed
to start back at time of inflation. Consequently the characteristic coupling function of the ST theories could attain a very
large value during the radiation epoch. Here ST cosmology in the radiation dominated universe is studied under such situation.
A general solution of the scale factor in the radiation dominated flat universe is obtained that is characterized by an additional
degree of freedom. An implication of this extra parameter is discussed.
相似文献
5.
On the basis of model properties of the expansive non-decelerative universe, the temperature at the end of the radiation era and of the present temperature of cosmic microwave background spectrum, the present parameters of our Universe can be determined.From model properties of the expansive non-decelerative universe and the temperature at the end of the radiation era follow: the hypothetical mass value of electron neutrino and the hypothetical values of the final parameters of the creative-expansive evolutionary phases of ultrastable expansive non-decelerative universes. 相似文献
6.
D. L. Khokhlov 《Astrophysics and Space Science》2013,343(2):787-790
Constraints of the laboratory physics on the model of the universe are considered. The constraints are derived from the measurement procedure for the flux of electromagnetic radiation and valid for any model of the universe. In classical physics, an observer in the frame of the detector can measure the transformation (1+z)?1 for the energy flux of the electromagnetic wave emitted in the frame of the source but cannot any transformation for space and time between the frames of the source and detector. In quantum mechanics, the energy of the electromagnetic radiation as a function of the distance may be measured as a redshifted frequency of photon (1+z) or as a decrease of the intensity of radiation (1+z). 相似文献
7.
In this paper it is suggested that inclusion of mutual gravitational interactions among the particles in the early dense universe
can lead to a ‘pre-big bang’ scenario, with particle masses greater than the Planck mass implying an accelerating phase of
the universe, which then goes into the radiation phase when the masses fall below the Planck mass. The existence of towers
of states of such massive particles (i.e. multiples of Planck mass) as implied in various unified theories, provides rapid
acceleration in the early universe, similar to the usual inflation scenario, but here the expansion rate goes over ‘smoothly’
to the radiation dominated universe when temperature becomes lower than the Planck temperature. 相似文献
8.
Walter Petry 《Astrophysics and Space Science》1994,222(1-2):127-145
A previously studied theory of gravitation in flat space-time is applied to homogeneous, isotropic cosmological models. In addition to radiation a two-component fluid model consisting of dust and of a background field is studied. This universe starts from a nonsingular state and expands for ever. The energy of radiation, of dust and of the background are emerged from the gravitational energy. Entropy is produced. The age of the universe is infinite measured in units of absolute time whereas the proper-time of the universe is finite. The sum of the density parameters of dust, of radiation and of the background field is about one. There is no flatness and no monopole problem. 相似文献
9.
Walter Petry 《Astrophysics and Space Science》1997,254(2):305-317
A nonsingular, homogeneous, isotropic cosmological model with cosmological constant in flat space-time theory of gravitation
is studied. The second law of thermodynamics yields a nonexpanding (nonstationary) universe without entropy production. At
the beginning of the universe radiation, matter and vacuum energy given by the cosmological constant are zero and then emerge
from gravitational energy. In the course of time the energy of radiation and matter decrease whereas the vacuum energy increases
forever. Light emitted from a distant galaxy loses energy on his way to the observer producing the observed redshift. The
velocity of light in the past is greater than the present one. This may explain superluminal velocities but only for large
redshifts. The sum of the density parameters of matter, radiation and vacuum energy is a little greater than one. All the
matter can be baryonic. There is no age problem of the universe.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
In this paper, we propose two new models in f(T) gravity to realize universe acceleration and phantom crossing due to dark torsion in the formalism. The model parameters
are constrained and the observational test are discussed. The best fit results favors an accelerating universe with possible
phantom crossing in the near past or future followed respectively by matter and radiation dominated era. 相似文献
11.
The evolution of a perfect fluid perturbation is considered in the radiation dominated period and in the dust epoch. In the investigation we make use of the general formalism developed in previous papers.It turns out that the evolution tendency is predicted by the state of the cosmic background. The radiation dominated universe does not stimulate growing processes of the perturbation, whereas the dust dominated universe causes a growing tendency of small perfect fluid formations. The results of this work are in accordance with these obtained by the present writers in a previous work. 相似文献
12.
Taishi Nakamoto Masayuki Umemura Hajime Susa 《Monthly notices of the Royal Astronomical Society》2001,321(4):593-604
Assuming simple dynamics for the growth of density fluctuations, we implement six-dimensional (6D) radiative transfer calculations to elucidate the effects of photon propagation during the reionization of an inhomogeneous universe. The ionizing sources are postulated to be AGN-like in this paper. The present simulations reveal that radiative transfer effects are still prominent considerably after the percolation epoch, in which patchy ionized regions connect with each other. In other words, owing to the collective opacity, the Universe does not become perfectly transparent against ionizing radiation even though strongly self-shielded regions disappear. It turns out that the inhomogeneity of the medium enhances the opacity effects and delays the end of reionization. Owing to such radiative transfer effects, the reionization in an inhomogeneous universe proceeds fairly slowly, in contrast to the prompt reionization in a homogeneous universe, and as a result the surface of reionization is not so sharply edged, but highly uneven. As a signature of the uneven surface of reionization, the cosmic IR background (CIB) radiation, which is produced by Ly photons resulting from radiative recombination, could exhibit strong anisotropies, reflecting the amplitude of density fluctuations at the reionization era. The predicted CIB intensity lies on a level of possible detection by forthcoming IR space telescope facilities. 相似文献
13.
The recently discovered accelerated expansion of the universe is of current interest in theoretical research on the evolution
of the universe. The cause of this behavior is presumably the presence of dark energy, which has been estimated to form up
to 70% of the universe and generates a “repulsive force.” In this paper a cosmological model is constructed which takes the
dark energy into account in a Jordan-Brans-Dicke tensor-scalar model with a dominant, nonminimally coupled scalar field in
the presence of a cosmological scalar. The radiation dominant epoch is discussed.
__________
Translated from Astrofizika, Vol. 51, No. 1, pp. 151–159 (February 2008). 相似文献
14.
In this paper we present a class of solutions of Einstein's field equations describing two-fluid models of the universe in
a locally rotationally symmetric Bianchi type II space-time. In these models one fluid is the radiation distribution which
represents the cosmic microwave background and the other fluid is the perfect fluid representing the matter content of the
universe. It is found that both the fluids are comoving in the locally rotationally symmetric Bianchi type II space-time.
The behaviour of the radiation density, matter density, the ratio of the matter density to the radiation density and the pressure
has been discussed. A subclass of solutions is found to describe models of a spatially homogeneous and partially isotropic
universe evolving from a radiation dominated era to a pressure free matter dominated era.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
The thermal decoupling during recombination and the endurance of this process can significantly deform the black-body background radiation spectrum even in the absence of heating sources. Observational data contradicts a flat standard universe but agrees with a low-density model and with a flat matter-antimatter symmetric universe. Evidence is presented against the presumption that matter-antimatter annibilation should necessarily produce large distortions. 相似文献
16.
Formation of black holes may be constrained by intrinsic parameters characterizing them such as electric charge. Here we discuss the effects of a relatively minute excess of charge on extremal black hole formation and the horizon. We extend the implications of this argument to the formation of primordial black holes (PBH) in the early universe which gives a possible reason for the lack of detection of Hawking radiation. These charge limits also apply to dark matter (DM) particles that may form PHBs in the early universe. The constraint thus obtained on the electric charge of DM particles could also account for the required magnitude of the repulsive dark energy (DE) currently causing an accelerated universe which provides a possible unified picture of DM and DE. 相似文献
17.
Tarun Souradeep 《Journal of Astrophysics and Astronomy》1997,18(4):231-240
In this talk I outline some of the arguments in support of a cosmological and primordial origin of the observed microwave
background radiation (MBR) in the early hot phase of the universe. This interpretation of the MBR is at the heart of the hot
Big Bang model (HBBM) of the universe. The observed Planckian energy distribution of the microwave photons reflects the thermal
equilibrium that can be set up naturally within HBBM in the dense early universe. Alternate interpretations face the challenge
of extremely tight constraints on deviations from a Planckian distribution. Within HBBM, the formation of large scale structure
is linked to tiny anisotropies in the angular distribution of the MBR photons. Recent measurements of these anisotropies seem
to be broadly consistent with the predictions of the current scenarios of structure formation in the universe. Since these
predictions are based on HBBM, the concurrence of data with theory provides additional support in favour of viewing the MBR
as the relic of Big Bang. 相似文献
18.
The thermal evolution of an inter-cluster gas of relativistic electrons heated by quasars with redshifts up toz=3 and 4 is studied in the framework of a Friedmann-Robertson-Walker universe. The gas cools by Compton scattering with the microwave backgroud radiation and by adiabatic cooling due to the universe expansion. Power and exponential laws of cosmological evolution of the comoving density of sources are considered. The obtained temperatures are sensitive to the form of these laws and to the heating epochs. Compared to the nonrelativistic models, the results obtained in the case of the power law present strong differences. These differences decrease when the exponential law is considered. Thermalization times are compared to the characteristic time of variation of the universe energy density and to the time-scales of energy loss by bremsstrahlung radiation and by Compton scattering. It is shown that, in some cases, nonequilibrium effects may be important. The time delay effects in the propagation of electromagnetic waves in cosmic plasma are shown to be very important for the analysis of theoretical models. 相似文献
19.
We investigate the validity of the generalized second law of gravitational thermodynamics in a non-flat FRW universe containing
the interacting generalized Chaplygin gas with the baryonic matter. The boundary of the universe is assumed to be enclosed
by the dynamical apparent horizon. We show that for the interacting generalized Chaplygin gas as a unified candidate for dark
matter and dark energy, the equation of state parameter can cross the phantom divide. We also present that for the selected
model under thermal equilibrium with the Hawking radiation, the generalized second law is always satisfied throughout the
history of the universe for any spatial curvature, independently of the equation of state of the interacting generalized Chaplygin
gas model. 相似文献
20.
This paper deals with the study of dynamical or phase space analysis of Bianchi I universe in Brans-Dicke gravity with chameleon scalar field. For this purpose, the matter contents are taken to be perfect fluid with magnetic field effects described by the non-linear Maxwell Lagrangian density. By taking some ansatz for the field potential and the interaction function in chameleon cosmology, we discuss three cases: Bianchi I universe with perfect fluid, FRW universe with magnetized perfect fluid and Bianchi I universe with magnetized perfect fluid. In all cases, we calculate fixed or critical points and discuss stability of the respective configuration for radiation as well as matter dominated eras. We also evaluate some cosmological parameters in each case for matter dominated era only and investigate their cosmological implications. 相似文献