共查询到20条相似文献，搜索用时 703 毫秒
1.
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
2.
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
3.
The solution of the Friedmann cosmological equations for the scale factor in a model of the Universe containing matter having the equation of state of dust and dark energy is considered. The equation-of-state parameter of the dark energy is taken to be an arbitrary constant w = ?1.006 ± 0.045, whose value is constrained by the current observational limits. An exact solution for the scale factor as a function of physical time and conformal time is obtained. Approximate solutions have been found for the entire admissible conformal time interval with an accuracy better than 1%, which exceeds the accuracy of the determined global parameters of our Universe. This is the first time an exact solution for the scale factor describing the evolution of the Universe in a unified way, beginning with the matter-dominated epoch and ending with the infinitely remote future, has been obtained. 相似文献
4.
V. V. Burdyuzha 《Astronomy Reports》2012,56(6):403-409
The evolution of the vacuum component of the Universe is studied in both the quantum and classical regimes. Our Universe has emerged as a result of a tunneling process, beginning with an oscillating mode and passing on to a Friedmann mode, and it very probably had a high symmetry for the Planck parameters. In the first fractions of a second (the quantum regime), as it cooled, the vacuum component of the Universe lost its high degree of symmetry due to phase transitions; i.e., its positive energy density was subject to negative contributions from quantum field condensates (by 78 orders of magnitude). After the last (quark-hadron) phase transition, the vacuum energy ??froze.?? At this time (10?6 s), the vacuum energy density can be calculated using the formula of Zel??dovich and substituting the mean values of the pseudo-Goldstone boson (??-mesons) masses characterizing the chromodynamic vacuum. Chiral symmetrywas lost at that time. The dynamics of the equilibrium vacuum after its ??hardening?? is considered using the holographic principle. During the next 4 × 1017 s (the classical regime), the vacuum component of the Universe was reduced by 45 orders of magnitude due to the creation of new quantum states during its expansion. It is possible to solve the cosmological-constant problem using the holographic principle, since the 123 problematic orders of magnitude disappear in usual physical processes. The vacuum energy density is also calculated in the classical regime to a redshift of 1011 using a ??cosmological calculator.?? 相似文献
5.
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
6.
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
7.
真空预压加固软土地基变形与固结计算研究 总被引：1，自引：0，他引：1
考虑真空度的衰减情况,对真空预压加固软基的变形和固结度计算方法进行了研究。先根据真空预压时砂井的真空压力状态建立了真空预压的空间轴对称变形模型,用位移法推导该模型在等应变条件下的变形及体积应变计算公式。在此基础之上结合Hansbo砂井地基固结理论和真空预压的边界条件,推导了忽略竖向渗流情况下的真空预压加固软土地基的固结解析解。比较文中计算方法与已有计算理论和现场试验实测资料结果表明,体积应变的计算对真空预压的孔压和固结度的计算有较大的影响,而直接引用传统堆载预压的体积应变计算公式计算会导致较大误差。在固结度计算中,采用Hansbo的近似方法能满足计算精度的要求,所得计算结果与实测结果吻合较好 相似文献
8.
Cosmological large numbers are studied using dimensional analysis. Expressions linking cosmological parameters with fundamental constants of the microworld are proposed. The Zel’dovich formula for the cosmological constant is generalized, and a series of characteristic masses of the Universe is derived. 相似文献
9.
A. D. Dolgov 《Astronomy Reports》2017,61(4):275-280
Astronomical observations of last few years have presented a surprising evidence that the Universe at redshift of order 10 is densely populated by supermassive black holes (quasars), supernovae, and contains very large amount of dust. All these data are in conflict with the canonical theory of quasar and supernova formation. A model is discussed which in a simple and natural way solves all these problem. In addition it explains an existence of supermassive black holes in each large galaxy and even in small ones. An inverted picture of galaxy formation is suggested when primordial black holes serve as seeds of galaxy formation. Simultaneously the origin and properties of black hole binaries, sources of gravitational waves registered by LIGO are explained. As a by-product the model may lead to abundant cosmological antimatter even in the Galaxy. 相似文献
10.
The standard equations of general relativity admit extension so that they can be supplemented, not only with Einsteinian cosmological
repulsive forces described by the Λ term, but also with other forces. Accordingly, we suggest a model of a uniformly expanding
Universe (an S model). In this model, the cosmological forces of attraction and repulsion precisely balance each other. This
S model is a good approximation for describing the Universe’s evolution over a wide range of redshifts (up to z ∼ 1000). The S model can explain in a simple way observational data on the age of the Universe, the apparent magnitude-redshift
relation for Type Ia supernovae, and the angular separation between the centers of neighboring bright spots against the uniform
background of the cosmic microwave background radiation. 相似文献
11.
底部抽真空预压法砂井地基固结解析解 总被引：1，自引：0，他引：1
基于谢康和等应变条件砂井地基固结理论和Hansbo砂井固结理论,考虑底部抽真空预压法加固方法中真空作用面位于固结土层底部的实际边界条件,推导出忽略竖向渗流情况下的底部真空预压加固地基固结方程解析解答。根据超孔压固结方程形成过程以及其解析解表达式,分析其与一般负压径向固结解答的区别。通过室内模型试验实测数据与解析模型计算结果的对比表明,不同位置处孔压和固结度计算值与实测结果吻合较好,从而验证了该模型的合理性,同时运用该模型也可有效验证已有关于底部抽真空室内模拟及现场原位试验结果。底部抽真空轴对称固结解析解可为底部抽真空技术的实际工程应用提供基础性的理论支持,推动底部抽真空技术的大规模推广应用。 相似文献
12.
Stability of earthquake moment tensor inversions: effect of the double-couple constraint 总被引：1，自引：0，他引：1
We show that spurious large non-double-couple components can be obtained in inversions for the full deviatoric moment tensor for shallow crustal earthquakes due to inaccurate Earth models. The traditional “best double-couple” solution does not in general provide an optimal estimate of a double-couple mechanism, and is only reliable when the non-double-couple component of the full deviatoric solution is small. The inverse problem for the moment tensors of the 1998 Antarctic Plate and 2000 Wharton Basin strike-slip earthquakes is shown in each case to have two well-fitting minima in the misfit function of pure double-couple solutions. Such pairs of solutions are most likely to exist for earthquakes which are close either to vertical strike-slip or to dip-slip on a fault plane dipping at 45°. It is shown theoretically that these pairs of solutions arise from the combination of the pure double-couple constraint and the instability of two elements of the moment tensor. No significant non-double-couple component is found for the shallow thrusting 1996 Biak, Indonesia earthquake. 相似文献
13.
We present a new normalization for the linear density-perturbation spectrum in a multi-parameter model of the Universe. Using the differential mass function for the nearly galaxy clusters obtained from optical data, we have constructed a functional relation between the dispersion of the density contrast σ 8 on the scale 8h ?1 Mpc and the cosmological parameters Ω m , ΩΛ, h, n, f v for each of three theoretical approximations of the mass function: Press-Schechter, Sheth-Tormen and Jenkins. An extended class of models of the Universe with general spatial curvature include four parameters for the matter components: baryons (Ω b ), “cold” dark matter (Ω c ), “hot” dark matter (Ω v ), and the vacuum energy (ΩΛ). It is shown that the most accurate normalization of the power spectrum is achieved with the Sheth-Tormen approximation. 相似文献
14.
自然界中矿物多以固溶体形式存在,据其晶体化学特征计算热力学性质是开展矿物成因理论研究的基础。本文引入描述二元矿物固溶体热力学性质的假三元模型,计算得到了透辉石-硬玉固溶体系列的热力学性质。该模型通过构造一种高度有序的中间相,同时考虑长程和短程有序效应,基于热力学平衡态矿物固溶体自由能最低的规律,可以计算特定组分下矿物的平衡自由能、焓和熵等热力学参数。本文针对透辉石-硬玉固溶体体系,取绿辉石为其中间有序态,计算了其活度-成分关系和温度-组分相图等,发现绿辉石随温度升高的有序无序相变为一级相变,相变温度为1 148±25 K,与实验研究结果一致。本文获得的透辉石-绿辉石-硬玉体系的热力学参数可用于视剖面图方法研究MORB成分的岩石的榴辉岩相变质作用过程。 相似文献
15.
Si-jie Liu Xue-yu Geng Hong-lei Sun Yuan-qiang Cai Xiao-dong Pan Li Shi 《国际地质力学数值与分析法杂志》2019,43(4):767-780
The system of vacuum pressure combined with vertical drains to accelerate soil consolidation is one of the most effective ground improvement methods. The consolidation theories of soft soil improved by vertical drains including void ratio–dependent compressibility and permeability have been widely applied in practice to predict the consolidation behavior. In this paper, analytical solutions of the consolidation of vertical drains are derived incorporating the loss and propagating stage of vacuum pressure. In addition, special solutions are obtained for the cases of instantaneous surcharge loading and staged surcharge loading, based on the general solution. The solution is verified by ignoring the propagating stage of vacuum pressure formation and comparing it with an existing solution. The effects of vacuum pressure loss and propagating stage combined with other parameters are investigated through the ratio between excess pore water pressure and surcharge loading. 相似文献
16.
A. A. Shatskii 《Astronomy Reports》2004,48(7):525-533
It is shown that Einstein-Rosen bridges (wormholes)—hypothetical objects that topologically connect separate locations in the Universe—can be static solutions of the Einstein equations. The corresponding equations for bridges are reduced to a form convenient for their analysis and numerical solution. The matter forming the bridge must have a sufficiently hard and anisotropic equation of state. Our results are compared with a previously known analytic solution for a bridge, which is a special case of the general solution in the framework of general relativity. The deflection of photons by the bridge (gravitational lensing) is studied. 相似文献
17.
We estimated the stress fields of the aftershocks of the 2000 western Tottori earthquake (Mw 6.6) and the northern Hyogo swarm (max Mw 5.2) by a stress tensor inversion of moment tensor solutions reported from the National Research Institute for Earth Science and Disaster Prevention (Japan). The maximum principal stress direction of the western Tottori sequence was estimated as N107°E with a strike–slip regime. In the northern Hyogo swarm, the orientations of the principal stress directions could not be well constrained by the observed data, but after examining the detailed characteristics of the solution, we obtained a most probable solution of N113°E for the σ1 direction. These solutions are consistent with the maximum horizontal directions roughly estimated from the strike directions of large earthquakes occurring geographically between these two seismic activities. We measured the angle between each fault–slip direction and maximum principal stress direction to investigate the frictional properties of earthquakes. The distribution of the angles was forward modeled to estimate the coefficient of friction and the stress ratio, assuming uniformly distributed fault orientations. For the western Tottori sequence, a homogeneous stress field with a coefficient of friction less than 0.4 was estimated. A high stress level was also suggested because very little change occurred in the stress field during the mainshock. For the northern Hyogo sequence, the coefficient of friction was estimated to be between 0.5 and 1.0. 相似文献
18.
G. Fodor 《Astronomy Reports》2018,62(12):874-881
Geons are localized horizonless objects formed by gravitational waves, held together by the gravitational attraction of their own field energy. In many respects they are similar to scalar field pulson/oscillon configurations, which were found numerically in 1976 by Kudryavtsev, Bogolyubskii, and Makhankov. If there is a negative cosmological constant, the spacetime of geons asymptotically approaches the anti-de Sitter (AdS) metric. AdS geons are time-periodic regular localized vacuum solutions without any radiation loss at infinity. A higher order perturbative construction in terms of an amplitude parameter shows that there are one-parameter families of AdS geon solutions emerging from combinations of identical-frequency linear modes of the system. 相似文献
19.
A method of constructing asymptotic solutions for nonlinear mean-field dynamo equations near the excitation threshold is developed
and applied to equations describing the solar dynamo in a Parker model. The form of solution obtained corresponds to the eigensolution
for a kinematic dynamo, for the intensity of the generation sources at which self-excitation of the magnetic field begins
(the so-called marginally stable eigenfunction). The wave amplitude is calculated. 相似文献
20.
利用Aleksandrowski推导的断层擦痕侧伏角公式,提出了一种改进的构造应力张量反演法。根据不同应力比值下构造应力与断层擦痕侧伏角的关系,利用最小二乘法,详细推导了构造应力张量的反演方法,最后利用Matlab软件编制程序实现了该计算过程。在此基础上,现场调查了江西武山铜矿北矿带的断层滑动数据,利用上述改进方法反演了该地区的构造应力张量方向特征。将上述反演结果与由震源机制解获得的最新构造应力场结果进行对比分析,并结合研究区断层的展布特征及所在的地质构造背景,获得了该地区自晚侏罗世以来的构造应力场特征,表明该地区构造应力场具有一定的稳定性。改进后的构造应力张量求解过程及工程应用表明,将Aleksandrowski的图示法和Etchecopar等的反演法结合起来反演构造应力张量,是对已有方法的改进,具有更加简单、实现容易等特点,计算结果比较符合实际。 相似文献