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1.
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.
In this paper the validity of the classical ionic model, using a Madelung term and a Born-Mayer repulsive term, is investigated quantatively for systems with a considerable overlap of the electron clouds of neighbouring ions, such as silicates with a high degree of polymerisation. A modified ionic model is presented which takes into account the spatial extent of the ions within the approximation of spherical atoms. Both models are tested against quantum mechanical electron densities and energies for SiO 4 4- -clusters. The data demonstrate the validity of the spherical atom approximation, producing a fit of 99.995%, and the importance of manybody effects maintaining the spherical symmetry of the electron clouds as contraction/expansion of the ions and charge transfer between ions. Although the new interaction potential is physically more plausible than the classical Born-Mayer model, both models reproduce the quantum mechanical potential surface with numerical accuracies of the same order of magnitude. The new model provides an improved tool for judging between ionic and non-ionic effects and for analysis of the quantum mechanical electron densities and interaction energies.  相似文献   

3.
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4.
A critical review of determinations of the number of spicules is presented, and the role of both classical and Type 2 spicules in heating and mass balance in the corona is considered. The total number of Type 2 spicules is determined, together with the upward fluxes of energy and mass to which they give rise. The total number of Type 2 spicules on the solar surface is found to be ~105, close to values obtained in other studies. The associated particle flux toward the corona is 2.5 × 1014 cm?2 s?1, an order of magnitude lower than the corresponding flux for classical spicules. The associated energy flux is 104 erg cm?2 s?1, an order of magnaitude lower than estimates obtained in other studies. The results indicate that Type 2 spicules can supply the mass lost from the corona, but are not able to fully explain coronal energy losses.  相似文献   

5.
The rotational effect of the cosmic vacuum is investigated. The induced rotation of elliptical galaxies due to the anti-gravity of the vacuum is found to be 10−21 s−1 for real elliptical galaxies. The effect of the vacuum rotation of the entire Universe is discussed, and can be described by the invariant ω ν = ω 0 ∼ $ \sqrt {G\rho v} $ \sqrt {G\rho v} . The corresponding numerical angular velocity of the Universe is 10−19 s−1, in good agreement with modern data on the temperature fluctuations of the cosmic background radiation.  相似文献   

6.
We test the hypothesis put forward by Bosma (1981) that the surface density of dark matter is proportional to the surface density of HI, using decompositions of the rotation curves of a number of galaxies according to the THINGS, along with data for the galaxy NGC 6822. The rotation curves of these galaxies can be explained by assuming the existence of a massive gaseous disk in the absence of a dark halo, although the proportionality factor ??dark/??HI between the surface densities of dark matter and HI is different for different galaxies. However, there emerges the problem of the gravitational stability of galaxies whose stellar-velocity dispersions have been estimated, if the thickness of the dark-matter disk is similar to or less than the thickness of the stellar disk. The proportionality between ?? dark and ??HI is probably due to the fact that the radial profiles of ??HI for galaxies with flat rotational curves are close to the critical density of a gravitationally stable gaseous layer (??HI ?? R ?1), and ??dark(R) for a pseudo-isothermal halo obeys the same law.  相似文献   

7.
VLBI observations of the quasar 3C 273 are analyzed. The physical parameters of the components in the parsec-scale jet of the quasar are estimated using amethod based on an inhomogeneous synchrotron sourcemodel. All the jet components (on scales of??0.1 pc) have magnetic fields that are either uniform or close to uniform, with magnitudes B ?? 0.1 G. The core component, which is probably associated with the central engine, differs from the remaining components in its unusually high density of relativistic electrons.  相似文献   

8.
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   

9.
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   

10.
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   

11.
Lunar mare basalts are a product of partial melting of the lunar mantle under more reducing conditions when compared to those expected for the Earth’s upper mantle. Alongside Fe, Ti can be a major redox sensitive element in lunar magmas, and it can be enriched by up to a factor of ten in lunar basaltic glasses when compared to their terrestrial counterparts. Therefore, to better constrain the oxidation state of Ti and its coordination chemistry during lunar magmatic processes, we report new X-ray absorption near edge structure (XANES) spectroscopy measurements for a wide range of minerals (pyroxene, olivine, Fe–Ti oxides) and basaltic melt compositions involved in partial melting of the lunar mantle. Experiments were conducted in 1 bar gas-mixing furnaces at temperatures between 1100 and 1300 °C and oxygen fugacities (fO2) that ranged from air to two orders of magnitude below the Fe–FeO redox equilibrium. Run products were analysed via electron microprobe and XANES Ti K-edge. Typical run products had large (>?100 µm) crystals in equilibrium with quenched silicate glass. Ti K-edge XANES spectra show a clear shift in energy of the absorption edge features from oxidizing to reducing conditions and yield an average valence for Fe–Ti oxides (armalcolite and ilmenite) of 3.6, i.e., a 40% of the overall Ti is Ti3+ under fO2 conditions relevant to lunar magmatism (IW ??1.5 to ??1.8). Pyroxenes and olivine have average Ti valence of 3.75 (i.e., 25% of the overall Ti is trivalent), while in silicate glasses Ti is exclusively tetravalent. Pre-edge peak intensities also indicate that the coordination number of Ti varies from an average V-fold in silicate glass to VI-fold in the Fe–Ti oxides and a mixture between IV and VI-fold coordination in the pyroxenes and olivine, with up to 82% [IV]Ti4+ in the pyroxene. In addition, our results can help to better constrain the Ti3+/∑Ti of the lunar mantle phases during magmatic processes and are applied to provide first insights into the mechanisms that may control Ti mass-dependent equilibrium isotope fractionation in lunar mare basalts.  相似文献   

12.
A model for the formation of supermassive black holes at the center of a cluster of primordial black holes is developed. It is assumed that ～10?3 of the mass of the Universe consists of compact clusters of primordial black holes that arose as a result of phase transitions in the early Universe. These clusters also serve as centers for the condensation of dark matter. The formation of protogalaxies with masses of the order of 2 × 108 M ⊙ at redshift z = 15 containing clusters of black holes is investigated. The nuclei of these protogalaxies contain central black holes with masses ～105 M ⊙, and the protogalaxies themselves resemble dwarf spherical galaxies with their maximum density at their centers. Subsequent merging of these induced protogalaxies with ordinary halos of dark matter leads to the standard picture for the formation of the large-scale structure of the Universe. The merging of the primordial black holes leads to the formation of supermassive black holes in galactic nuclei and produces the observed correlation between the mass of the central black hole and the bulge velocity dispersion.  相似文献   

13.
The gases released from a molybdenum crucible, as used in K/1bAr dating, were measured dynamically using a mass spectrometer. Mass 28 was the principle component but the amount of argon-40 (≈ 5 · 106 cm3 / S.T.P. for a 4.5- g crucible) may be an important source of atmospheric contamination, and limit the precision of age determination in young, or low-potassium rocks.The amount of argon could be reduced by about two orders of magnitude by degassing the crucible; however, this improvement was reduced to one order if the degassed crucible was allowed to come in contact with the atmosphere.The heated glass sides of the fusion dome did not contribute a significant amount of gas.  相似文献   

14.
To investigate the point defect chemistry and the kinetic properties of manganese olivine Mn2SiO4, the point defect relaxation time (τ) characterizing the rate of re-equilibration of electrical conductivity following a change in oxygen fugacity was measured for single crystals oriented for electrical conduction along the [010] direction. The experiments were carried out at temperatures T = 1173–1473 K and oxygen fugacities with the MnSiO3 activity controlled at unity. The value of τ, which ranges from 130 to 1463 s, increases with decreasing temperature. At 1273 K, the value of τ in the regime is a factor of ∼1.8 smaller than that in the regime. The point defect relaxation time was used to calculate the chemical diffusivity (). Values of lie in the range 2.2× 10− 10 − 2.5×10− 9 m2/s. For the regime, a semi-log plot of vs 1/T yields a concave downward curve. Based on these results combined with those from Part I of this work for the point defect structure and electrical conductivity in Mn-olivine, it is proposed that the relaxation rate of electrical conduction is determined by the coupled diffusion of manganese vacancies and electron holes which rate-control the relaxation process at low and high temperatures, respectively. Deconvolution of the curve into two straight-line segments yields values for the mobilities and the diffusivities for Mn vacancies and electron holes. These results, combined with the measured electrical conductivity data, were used to calculate the concentrations of Mn vacancies and electron holes. These results in conjunction with those published for other transition-metal silicate olivines reveal the following: The mobility of electron holes in Mn-olivine is about two orders of magnitude smaller than that in Fe-olivine and is somewhat larger than that in (Mg0.9Fe0.1)-olivine. The mobilities of metal vacancies in these three olivines are similar both in magnitude and in temperature dependence. The concentrations of the majority point defects are the highest in Fe-olivine crystals and the lowest in Co-olivine crystals, while those in Mn-olivine and (Mg0.9Fe0.1)-olivine crystals lie in between. The deviation from stoichiometry in the cation sublattice for a transition-metal silicate olivine is about two orders of magnitude lower than that for the corresponding transition-metal oxide. Received: 10 January 1996 / Revised, accepted: 29 May 1997  相似文献   

15.
The frequency-dependence of the shear viscosity and modulus of rhyolite melt has been determined over a 10–14 log10 Pa s viscosity range and a 0.03–63 rad s–1 angular frequency range. The frequency-dependent viscosity determined at high frequencies is 5 orders of magnitude lower than the Newtonian viscosity. At lower frequencies, a frequency-independent viscosity identical with the Newtonian viscosity is observed. The measured shear modulus increases from zero to 30.5 ± 2.5 GPa with increasing frequency. The viscoelastic regime consists of a maximum in viscous loss centered on the Max-well relaxation time. The width and height of the loss modulus as a function of frequency is inconsistent with a single relaxation-time. The frequency-dependent shear modulus is best described by a distribution of relaxation-times with a sharp cutoff at times slightly longer than the Maxwell relaxation time, and a long tail at shorter times extending up to 5 orders of magnitude less than the Maxwell relaxation time. This distribution of relaxation-times is in contrast with the single-relaxation-time behavior observed in low viscosity silicate melts.  相似文献   

16.
The effect of intergranular water on the conductivity of polycrystalline brucite, Mg(OH)2, was investigated using impedance spectroscopy at 2 GPa, during consecutive heating–cooling cycles in the 298–980 K range. The grain boundary hydration levels tested here span water activities from around unity (wet conditions) down to 10−4 (dry conditions) depending on temperature. Four orders of magnitude in water activity result in electrical conductivity variations for about 6–7 orders of magnitude at 2 GPa and room temperature. Wet brucite samples containing, initially, about 18 wt% of evaporable water (i.e. totally removed at temperatures below 393 K in air), display electrical conductivity values above 10−2–10−3 S/m. A.C. electrical conductivity as a function of temperature follows an Arrhenius behaviour with an activation energy of 0.11 eV. The electrical conductivity of the same polycrystalline brucite material dried beforehand at 393 K (dry conditions) is lower by about 5–6 orders of magnitude at room temperature and possesses an activation energy of 0.8–0.9 eV which is close to that of protonic diffusion in (001) brucitic planes. Above ca. 873 K, a non-reversible conductivity jump is observed which is interpreted as a water transfer from mineral bulk to grain boundaries (i.e. partial dehydration). Cooling of such partially dehydrated sample shows electrical conductivities much higher than those of the initially dry sample by 4 orders of magnitude at 500 K. Furthermore, the corresponding activation energy is decreased by a factor of about four (i.e. 0.21 eV). Buffering of the sample at low water activity has been achieved by adding CaO or MgO, two hygroscopic compounds, to the starting material. Then, sample conductivities reached the lowest values encountered in this study with the activation energy of 1.1 eV. The strong dependency of the electrical conductivity with water activity highlights the importance of the latter parameter as a controlling factor of diffusion rates in natural processes where water availability and activity may vary grandly. Water exchange between mineral bulk and mineral boundary suggests that grain boundary can be treated as an independent phase in dehydroxylation reactions.  相似文献   

17.
Preliminary tests of a prototype radio-frequency quadrupole (RFQ) collision cell system, known as an isobar separator for anions (ISA), for the removal of isobaric interferences for accelerator mass spectrometry (AMS) and for studies of anion–gas interactions are reported. The ISA decelerated a mass-analysed beam of anions from an energy (∼ 20 keV) typically generated by an AMS ion source to < 10 eV. RFQs and electrostatic lenses then guided the ions through the collision cell where ion-gas collisions reduced both the energy and energy spread of the ion beam (cooled the ions) and ion-gas reactions attenuated most of the unwanted isobars. The anions were then re-accelerated to their original energy for injection into the rest of the AMS system. With the ISA installed on a full 3 MV AMS system, attenuations of 32S-, 12C3- and 39K- by six, seven and greater than ten orders of magnitude, respectively were achieved using 0.7–1 Pa NO2 gas in the collision cell, while maintaining approximately 10–30% of the chlorine anion transmission. A further measurement of a 36Cl/Cl = 4.1 × 10-11 RM is also described. The results suggest that the 36Cl/Cl lower detection limit of the current system was 10-14–10-15 for samples that could be prepared with S/Cl ratios below 10 μg g-1.  相似文献   

18.
The physical conditions in the radio sources CTA 21 and OF+247 are studied assuming that the low-frequency spectral turnovers are due to synchrotron self-absorption. The physical parameters of the radio sources are estimated using a technique based on a nonuniform synchrotron source model. It is shown that the magnetic-field distributions in the dominant compact components of these radio sources are strongly inhomogeneous. The magnetic fields at the center of the sources are B ～ 10?1 G, and the fields are two to three orders of magnitude weaker at the periphery. The magnetic field averaged over the compact component is B ～ 10?3 G, and the density of relativistic electrons is n e ～ 10?3 cm?3. Assuming that there is equipartition of the energies of the magnetic field and relativistic particles, averaged over the source, 〈E H 〉 = 〈E e 〉 ～ 10?7–10?6 erg cm?3. The energy density of the magnetic field exceeds that of the relativistic electrons at the centers of the radio sources. The derived parameters of CTA 21 and OF+247 are close to those of the hot spots in the radio galaxy Cygnus A. On this basis, it is suggested that CTA 21 and OF+247 are radio galaxies at an early stage of their evolution, when the hot spots (dominant compact radio components) have appeared, and the radio lobes (weak extended components) are still being formed.  相似文献   

19.
The statistical dependence of τ/(DM)2 (the ratio of the broadening of a pulsar pulse due to scattering in the interstellar medium to the square of the pulsar’s dispersion measure) on the pulsar’s dispersionmeasure, Galactic coordinates, age, and the angular distance to the nearest supernova remnant are studied. This parameter describes the relative level of electron density fluctuations in the turbulent interstellar plasma. It is shown that the interstellar plasma turbulence level is three orders of magnitude higher in the spiral arms of the Galaxy than outside the arms. The plasma turbulence level is approximately an order of magnitude higher in the Galactic arms, in regions within ?0.3° of supernova remnants, than outside these regions. We conclude that the source of energy for the turbulence in the Galactic arms is supernova explosions in the denser medium there.  相似文献   

20.
Tkachev  M. V.  Pilipenko  S. V.  Carlesi  E. 《Astronomy Reports》2019,63(5):372-377

The entropy approach to the problem of the formation of a dark-matter halo is analyzed and verified. The model described predicts that the density profile of the halo is determined by the sum of the initial entropy associated with fluctuations of the matter density in the early Universe and the entropy generated in the course of the formation of the halo. The model also predicts the formation of halos without cusps in most galaxies with high initial entropy. Special numerical models are used to measure the initial entropy of the halo, which proves to be an order of magnitude lower than the values calculated using the linear theory, suggesting that most galactic-mass halos should possess cusps.

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