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1.
The interaction of matter and radiation in a hot-model universe   总被引：3，自引：0，他引：3  
In this paper we continue the investigation initiated by Weymann as to the reason why the spectrum of the residual radiation deviates from a Planck curve. We shall consider the distortions of the spectrum resulting from radiation during the recombination of a primeval plasma. Analytical expressions are obtained for the deviation from an equilibrium spectrum due to Compton scattering by hot electrons. On the basis of the observational data it is concluded that a period of neutral hydrogen in the evolution of the universe is unavoidable. It is shown that any injection of energy att>1010 sec (red shiftz<105) leads to deviation from an equilibrium spectrum.Translated by Peter Foukal.  相似文献   

2.
活动星系核的高能辐射机制研究对于揭示其结构和演化特征以及中央驱动之迹具有其重要的意义。近十年来，随着活动星系统结构模型研究以及其高能连续谱观测的发展，解释活动星系统高能辐的非热致电子级联模型得以产生、发展和完善起来。  相似文献   

3.
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   

4.
In this work we investigate the background dynamics when dark energy is coupled to dark matter with a suitable interaction in the universe described by brane cosmology. Here DGP and the RSII brane models have been considered separately. Dark energy in the form of modified Chaplygin gas is considered. A suitable interaction between dark energy and dark matter is considered in order to at least alleviate (if not solve) the cosmic coincidence problem. The dynamical system of equations is solved numerically and a stable scaling solution is obtained. A significant attempt towards the solution of the cosmic coincidence problem is taken. The statefinder parameters are also calculated to classify the dark energy models. Graphs and phase diagrams are drawn to study the variations of these parameters. It is also seen that the background dynamics of modified Chaplygin gas is completely consistent with the notion of an accelerated expansion in the late universe. Finally, it has been shown that the universe in both the models follows the power law form of expansion around the critical point, which is consistent with the known results.  相似文献   

5.
Induced Compton scattering by independent relativistic particles in a radiation field is considered from both quantum mechanical and classical viewpoints. Quantum mechanically, the particle recoil causes an imperfect cancellation of the induced scattering rates between pairs of photon states. This results in a net energy transfer from the radiation field to the particle. Classically, the electrodynamical effects are manifestations of non-linear coupling between different wave amplitudes in the equation of motion. The results from these two approaches are related and shown to be equivalent.  相似文献   

6.
In this note extended Chaplygin gas equation of state includes bulk and shear viscosities suggested. Bulk viscosity assumed as power law form of density and shear viscosity considered as a constant. We study evolution of dark energy density numerically for several forms of scale factor, and analytically under some assumptions corresponding to early universe. We found our model is stable for infinitesimal viscous parameters.  相似文献   

7.
In this letter, we have considered a flat FRW universe. Instead of considering only one candidate for the dark energy, we have considered the interaction between phantom field and modified Chaplygin gas. It has been shown that the potential of the phantom field increases from a lower value with evolution of the universe. It has been observed that the field has an increasing tendency and the potential has also an increasing tendency with passage of cosmic time. In the evolution of the universe the crossing of w=−1 has been realized by this interacting model.  相似文献   

8.
Compton scattering of electromagnetic radiation in pulsar magnetospheres   总被引：2，自引：0，他引：2  
We have considered the spontaneous Compton scattering of radiation in the magnetic field by both a single ultra-relativistic electron and a system of electrons with the power-law energy distribution. The degree of radiation anisotropy was assumed arbitrary. Parameters of the scattering-generated radiation for the entire range of post-scattering photon energies are given in the paper for all possible scattering modes.  相似文献   

9.
Equations describing the evolution of isotropic distributions of unpolarized electromagnetic waves and of scattering of any energy due to spontaneous and induced Compton scattering are derived in the semi-classical approximation for unshielded particles.It is shown that induced Compton scattering of high frequency waves by relativistic electrons in synchrotron sources is a negligible effect contrary to the conclusions of Oster (1968b) and of Kaplan and Tsytovich (1969).  相似文献   

10.
In this paper, we have considered a model of our universe containing five components as its constituents. Then, we have done here the statefinder diagnostics for this model. This model can successfully explain the accelerated expansion of the universe given that it satisfies a certain condition. Here we have considered the modified Chaplygin gas as the dynamically changing part of the dark energy component of our universe. Chaplygin gas provides early deceleration and late time acceleration of the universe. The graphical representation of statefinder parameters shows that the total evolution of the universe starts from radiation era to phantom model.  相似文献   

11.
In this work we explore the background dynamics when dark energy is coupled to dark matter with a suitable interaction in the universe described by brane cosmology. Here DGP and the RSII brane models have been considered separately. Dark energy in the form of Generalized Cosmic Chaplygin gas is considered. A suitable interaction between dark energy and dark matter is considered in order to at least alleviate (if not solve) the cosmic coincidence problem. The dynamical system of equations is solved numerically and a stable scaling solution is obtained. A significant attempt towards the solution of the cosmic coincidence problem is taken. The statefinder parameters are also calculated to classify the dark energy models. Graphs and phase diagrams are drawn to study the variations of these parameters. It is also seen that the background dynamics of Generalized Cosmic Chaplygin gas is consistent with the late cosmic acceleration, but not without satisfying certain conditions. It has been shown that the universe in both the models follows the power law form of expansion around the critical point, which is consistent with the known results. Future singularities were studied and our models were declared totally free from any types of such singularities. Finally, some cosmographic parameters were also briefly studied. Our investigation led to the fact that although Generalized cosmic Chaplygin gas with a far lesser negative pressure compared to other dark energy models, can overcome the relatively weaker gravity of RS II brane, with the help of the negative brane tension, yet for the DGP brane model with much higher gravitation, the incompetency of Generalized cosmic Chaplygin gas is exposed, and it cannot produce the accelerating scenario until it reaches the phantom era.  相似文献   

12.
During the period of 1991–1993 two strong high energy γ-ray flares were observed by the Compton Gamma Ray Observatory in the flat spectrum radio source PKS 0528+134. They were associated with strong mm-radio outbursts with a few months time-delays. In this paper the spectral energy distributions (SED) of the radiations in the γ-hand X-ray and the IR-optical bands are analysed. It is shown that the high energy γ-ray radiation may be due to the inverse Compton scattering of the ambient UV and soft X-ray photons by the relativistic electrons in the jet. Basing on the comparison between the properties of the synchrotron radiation of the γ-ray source and the spectral evolution of the mm-radio outbursts, the evolutional relationship between the γ-ray emitting blobs and the mm-radio emitting blobs is discussed.  相似文献   

13.
In this letter, I have proposed a model of variable modified Chaplygin gas and shown its role in accelerating phase of the universe. I have shown that the equation of state of this model is valid from the radiation era to quiessence model. The graphical representations of statefinder parameters characterize different phase of evolution of the universe. All results presented in the letter concerns the case k=0.  相似文献   

14.
A model of intergalactic medium heated by QSOs and cooled by the expansion of the universe and Compton cooling is studied in the framework of a Friedmann-Robertson-Walker universe. Cosmological evolution functions of the comoving density of QSO's as well as the case of no evolution are considered. The theoretical X-ray background spectrum (through thermal bremsstrahlung) and Comptony parameter are calculated including relativistic corrections in the electron-electron, electron-proton and electron-photon interactions. The observed X-ray background and the upper limit of the Compton parametery cobe given by the COBE satellite are used to adjust, for each value of reheating redshiftsz c ranging from 0.1 to 5.0, the present values of the temperatureT 0 and densityn 0 of the intergalactic gas. Forz c > 0.25, when the theoretical X-ray spectrum fits the observed one, the adjusted values ofT 0 andn 0 imply iny >y cobe. On the other hand, whenT 0 andn 0 are consistent withy cobe, the calculated X-ray spectrum is lower than the observed one. Unless 100% of the observed X-ray background is due to discrete sources and if the intergalactic medium contributes more than 2.5% to such background we come to the interesting result that the medium must have been heated atz c < 1. In this case we shall have to explain the high energy rates necessary to heat the intergalactic medium. Forz c 0.25, it is possible to find values ofT 0 andn 0 such that both the calculated X-ray background and the y parameter simultaneously reproduce the corresponding observed values. However, in this case, unless it could be shown to be otherwise by future observations or theoretical studies, it seems that the model of hot intergalactic medium is not plausible because of the high energies required to heat the intergalactic gas.  相似文献   

15.
The main goal of this work is investigation of NADE in the cyclic universe scenario. Since, cyclic universe is explained by a phantom phase (ω<−1), it is shown when there is no interaction between matter and dark energy, ADE and NADE do not produce a phantom phase, then can not describe cyclic universe. Therefore, we study interacting models of ADE and NADE in the modified Friedmann equation. We find out that, in the high energy regime, which it is a necessary part of cyclic universe evolution, only NADE can describe this phantom phase era for cyclic universe. Considering deceleration parameter tells us that the universe has a deceleration phase after an acceleration phase, and NADE is able to produce a cyclic universe. Also it is found valuable to study generalized second law of thermodynamics. Since the loop quantum correction is taken account in high energy regime, it may not be suitable to use standard treatment of thermodynamics, so we turn our attention to the result of Li et al. (Adv. High Energy Phys. 2009: 905705, 2009), which the authors have studied thermodynamics in loop quantum gravity, and we show that which condition can satisfy generalized second law of thermodynamics.  相似文献   

16.
Cosmological solutions in the presence of an imperfect fluid and zero-mass scalar field are obtained in higher derivative theory. We investigate both power law and exponential expansion of the universe described by full causal theories proposed by Israel and Stewart. It is observed that energy density, co-efficient of bulk viscosity decrease with time in the presence of massless scalar field and temperature increase with expansion of universe.  相似文献   

17.
Quasars, pulsars and other cosmic sources of intense radiation are known to have large brightness temperature (kT b?mc 2) and relativistic electron density values. In this case the induced Compton scattering by relativistic electrons should be considered. The probability of scattering with decreasing radiation frequency is derived for isotropic radiation scattering. When induced scattering takes place, the relativistic electron obtains its energy by transforming high-frequency quanta into the low-frequency ones. In the most intensive sources electrons would receive energiesE?mc 2 ××(kT b/mc 2)1/7 due to the heating rate proportional toE ?5 with the cooling rate proportional toE 2. Considerable distortion of the quasar spectrum is possible for reasonably large values of relativistic electron density (N?106cm?3) notwithstanding that the heating is negligible. In pulsars relativistic electron heating and spectrum distortion appear to depend more on the induced Compton scattering.  相似文献   

18.
本文认为强磁场中的逆Compton散射可能是γ射线爆的主要辐射机制.其能谱是由源区质子产生的低频光子经强磁场中非热电子的Compton散射形成的.我们利用非相对论情形(B/B_(cr)≤1,hv_i/m_ec~2≤1)下强磁场中的Compton散射微分截面,导出了上述Compton散射的辐射谱公式,由此很好地拟合了典型γ射线爆GB811016的观测能谱.  相似文献   

19.
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   

20.
An expression for the radiation pressure in high density plasma is derived on the basis of plasma waves and semiclassical theory of radiation. Comparison of our result with that of Planck, Sommerfeld and Landau and Lifshitz is briefly discussed. It is shown that the radiation pressure in a high density plasma is not just one third of the corresponding energy density because of the different dependence on the index of refraction n (ω). Possible applications to the thermal history of early universe and late stage stellar evolution are also stressed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

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