摘要:This paper studies the existence and stability of the artificial equilibrium points (AEPs) in the low-thrust restricted three-body problem when both the primaries are oblate spheroids. The artificial equilibrium points (AEPs) are generated by canceling the gravitational and centrifugal forces with continuous low-thrust at a non-equilibrium point. Some graphical investigations are shown for the effects of the relative parameters which characterized the locations of the AEPs. Also, the numerical values of AEPs have been calculated. The positions of these AEPs will depend not only also on magnitude and directions of low-thrust acceleration. The linear stability of the AEPs has been investigated. We have determined the stability regions in the xy, xz and yz-planes and studied the effect of oblateness parameters A1(0A1?and ?A2(0A2<1) on the motion of the spacecraft. We have found that the stability regions reduce around both the primaries for the increasing values of oblateness of the primaries. Finally, we have plotted the zero velocity curves to determine the possible regions of motion of the spacecraft.
摘要:An instructive analogy between the deformation of a pinched elastic cylindrical shell and the anti-gravity behind accelerated cosmic expansion is established. Subsequently the entire model is interpreted in terms of a hyperbolic fractal Rindler space-time leading to the same robust results regarding real energy and dark energy being 4.5% and 95.5% respectively in full agreement with all recent cosmological measurements.
摘要:We analyse the possibility that the observed cosmological redshift may be cumulatively due to the expansion of the universe and the tired light phenomenon. Since the source of both the redshifts is the same, they both independently relate to the same proper distance of the light source. Using this approach we have developed a hybrid model combining the Einstein de Sitter model and the tired light model that yields a slightly better fit to Supernovae Ia redshift data using one parameter than the standard ΛCDM model with two parameters. We have shown that the ratio of tired light component to the Einstein de Sitter component of redshift has evolved from 2.5 in the past, corresponding to redshift 1000, to its present value of 1.5. The hybrid model yields Hubble constant H0 =69.11(±0.53)km·s-1 ·Mpc-1 and the deceleration parameter q0 =-0.4. The component of Hubble constant responsible for expansion of the universe is 40% of H0 and for the tired light is 60% of H0. Consequently, the critical density is only 16% of its currently accepted value;a lot less dark matter is needed to make up the critical density. In addition, the best data fit yields the cosmological constant density parameter =0. The tired light effect may thus be considered equivalent to the cosmological constant in the hybrid model.
摘要:We study galaxy distributions with Sloan Digital Sky Survey SDSS DR14 data and with simulations searching for variables that can constrain neutrino masses. To be specific, we consider the scenario of three active neutrino eigenstates with approximately the same mass, so Σmv=3mv. Fitting the predictions of the ΛCDM model to the Sachs-Wolfe effect, σ8, the galaxy power spectrum Pga1(k) , fluctuations of galaxy counts in spheres of radii ranging from 16/h to 128/h Mpc, Baryon Acoustic Oscillation (BAO) measurements, and h=0.678±0.009, in various combinations, with free spectral index n, and free galaxy bias and galaxy bias slope, we obtain consistent measurements of Σmv. The results depend on h, so we have presented confidence contours in the (Σmv, h) plane. A global fit with h=0.678±0.009 obtains eV, and the amplitude and spectral index of the power spectrum of linear density fluctuations P(k): , and n=1.021±0.075. The fit also returns the galaxy bias b including its scale dependence.
摘要:The origin of ultra high energy cosmic rays (UHECRs) is still an open question in astroparticle physics. TeV blazars are a small group of active galactic nuclei (AGNs). They all have been observed in TeV gamma ray band, and show violent variabilities in flux at all wavelengths. So it is believed that they have abilities to produce UHECRs. To judge whether the TeV blazars can be the candidates of the origin of UHECRs, we collect the information of emission region of 38 TeV blazars, and estimate the maximum energy that the charged particle can be accelerated there. The results show that TeV blazars have abilities to accelerate cosmic rays to the energy above 1018?eV, some even higher than 1020?eV, and they may be the sources of UHECRs.
摘要:An enhancement in the number of galaxies as function of the redshift is visible on the SDSS Photometric Catalogue DR 12 at z = 0.383. This over-density of galaxies is named the Great Wall. This variable number of galaxies as a function of the redshift can be explained in the framework of the luminosity function for galaxies. The differential of the luminosity distance in respect to the redshift is evaluated in the framework of the LCDM cosmology.
摘要:It is now established that entanglement in the sense of local non-factorizability of two or more degrees of freedom of a system occurs in classical polarization optics. We extend the idea to weak gravitational waves which are strikingly similar to optical waves. It is shown that a linearized classical gravity wave can in principle get entangled in the sense mentioned with the vibrational modes of an array of test masses in a plane perpendicular to its direction of propagation. A Bell-CHSH inequality based on the requirement of noncontextuality for classical realism is derived, and it is shown that the putative nonfactorizable state violates this inequality. The idea is therefore empirically falsifiable.
摘要:The chromaticity of solar spectrum is studied with the help of a Solar Spectrum Monitor system that can detect individual color in the spectrum. Recent observations done by the detector on the Solar Radiation and the Erath Milieu Experiment suggest that the sun’s visible spectral irradiance changes from May 2009 to September 2012. The data of Earth’s coordinates and environment have been taken since April 2005 after the devastating Tsunami (December, 2004) of India. The bizarre data of?zenith angle,?azimuth angle, and?temperature?of the Earth’s atmosphere show their changes of maxima and minima epoch to epoch. The data of solar spectrum monitor have been taking since 2009 and significant transformations of colored ratios?ΔRB/W?and?ΔRR/W?per hour are observed among the regions of each solstice between 2009 and 2012. The author advocates that the abrupt vagaries of the Earth’s movements may cause devastating tsunamis, earthquake, volcanic eruption, cyclones and tornadoes in addition of anomalous changes of solar spectral irradiation, humidity, temperature and pressure;those effects may spoil ecological balance and extinct some living species from the soil of the earth.
摘要:We have presented the evolution of angular momentum and orbital period changes between the component spins and the orbit in close double white dwarf binaries undergoing mass transfer through direct impact accretion over a broad range of orbital parameter space. This work improves upon similar earlier studies in a number of ways: First, we calculate self-consistently the angular momentum of the orbit at all times. This includes gravitational, tides and mass transfer effects in the orbital evolution of the component structure models, and allow the Roche lobe radius of the donor star and the rotational angular velocities of both components to vary, and account for the exchange of angular momentum between the spins of the white dwarfs and the orbit. Second, we investigate the mass transfer by modeling the ballistic motion of a point mass ejected from the center of the donor star through the inner Lagrangian point. Finally, we ensure that the angular momentum is conserved, which requires the donor star spin to vary self-consistently. With these improvements, we calculate the angular momentum and orbital period changes of the orbit and each binary component across the entire parameter space of direct impact double white dwarf binary systems. We find a significant decrease in the amount of angular momentum removed from the orbit during mass transfer, as well as cases where this process increases the angular momentum and orbital period of the orbit at the expense of the spin angular momentum of the donor and accretor. We find that our analysis yields an increase in the predicted number of stable systems compared to that in the previous studies, survive the onset of mass transfer, even if this mass transfer is initially unstable. In addition, as a consequence of the tidal coupling, systems that come into contact near the mass transfer instability boundary undergo a phase of mass transfer with their orbital period.
摘要:We present a study of the pre-protostellar core (PPC) L1498. A series of self-consistent, three-dimensional continuum radiative transfer models are constructed. The outputs of these models are convolved with appropriate telescope beam responses, including the effect of beam chopping to simulate SCUBA observations. The simulated observations are compared with existing observational data. An automated search is conducted in the multi-dimensional parameter space to identify the best-fit model. Grids of models are constructed in the vicinity of the best fit in order to understand the sensitivity/uncertainty of the results. We find that the source is well fit by a prolate spheroid of cutoff (and thus approximately outer) radius rcut = 0.073 ± 0.005 pc, axis ratio q = 2.0 ± 0.2, a central luminosity L* -3 Lsun, and an optical depth in the visible of τv = 20 ± 5. We find that the PPC is illuminated by two external radiation fields: a uniform ISRF of strength sISRF= 0.5 ± 0.25 and a local plane-parallel radiation field sPPRF = 1.0 ± 0.5. Both of these radiation fields are locally attenuated, with τISRF = 1.0 ± 0.25, and τPPRF = 1.25 ± 0.75, consistent with the fact that L1498 is embedded in a larger cloud. Most interestingly, the density fall-off at the outer edge is extremely steep, having a power law of m > 10. This is effectively a “sharp edge” to the PPC, and together with the constant density interior, is interpreted as potential signs of a pressure-confined core.
摘要:Coupling effects of Earth oblateness and direct solar radiation pressure on the motion of an artificial satellite are evaluated. Secular and periodic terms are retained up to order three and two respectively, where the coefficient of the second zonal harmonic of the geopotential is considered of first order. The solution revealed the existence of secular terms at order three that arises from the couplings between terms, of lower orders, resulting from the solar radiation pressure.
摘要:The present work studies the stability condition of central control artificial equilibrium points of the planar circular restricted problem of 2 + 2 bodies (PCRP2 + 2B) and also its variant when the shape of larger mass is taken to be an oblate spheroid. We find that the paper will be of great application in choosing an artificial equilibrium point (AEP) in the neighbourhood of numerous planets e.g. Jupiter or the bodies which provide a model of the problem studied. The minimum thrust will save a quantum of energy to be applied to have an arbitrary point as a chosen starter. For solar sailing and magnetic force this minimum thrust will be of great use.
摘要:Considering Bianchi type III space-time we present the model Universe containing strange quark matter which is expanding, anisotropic, with a sign of dark energy that help in accelerated expansion of this Universe. It is also seen that the model Universe contains both particles and strings but ultimately will have fluid containing particles only. This model which we consider here is acceptable in view of the present observations of the Universe. Some physical and geometrical properties are also discussed.
摘要:Current progress in cosmic microwave background (CMB) anisotropy measurements opens up the possibility of determining Hubble’s constant (H0 = h × 100 km s−1 Mpc−1) from the CMB power spectrum radiation temperature anisotropy. The results show that, besides the Lambda cold dark matter (ΛCDM) model, much simpler Einstein-de Sitter (EdeS) models without the cosmological constant can fit the data as well, or even better, than the ΛCDM model. Calculations with EdeS models yield unexpectedly low values for Hubble’s constant of h = 0.30 and 0.46, respectively. These values are completely inconsistent with the direct determination of h ~ 0.70 from the redshift (RS) of spectral lines. In the present paper I consider whether the gap between h = 0.3 and h = 0.7 could be explained using conventional physics without introducing further hypotheses, or whether the RS of starlight and the RS of the CMB could stem from different physical origins.
摘要:The luminosity function (LF) for stars is here fitted by a Schechter function and by a Gamma probability density function. The dependence of the number of stars on the distance, both in the low and high luminosity regions, requires the inclusion of a lower and upper boundary in the Schechter and Gamma LFs. Three astrophysical applications for stars are provided: deduction of the parameters at low distances, behavior of the average absolute magnitude with distance, and the location of the photometric maximum as a function of the selected flux. The use of the truncated LFs allows modeling the Malmquist bias.
摘要:In this paper we study some van den Bergh open clusters combining photometry and astrometry. A model which analyses the proper motion distribution and the stellar density is applied to find the kinematic parameters and stellar membership in the region of the open clusters vdB92, vdB146 (NGC 7129) and vdB150. The astrometric data are obtained from UCAC4 catalogue. The centre coordinates, the components of mean proper motion, the angular diameter and the astrometric members are reported, taking the following values: for vdB92: α=105.97281°±0.13113°, δ=−11.57814°±0.10575°,?μαcosδ=−3.46±0.19mas/yr,μδ=1.27±0.19mas/yr, 34', 60 members;for vdB146: α=325.78423°±0.15297°, δ=66.13575°±0.02907°, μαcosδ=−2.71±0.25mas/yr, μδ=−3.32±0.25mas/yr, 9', 5 members;and for vdB150: α=332.22519°±0.06074°, δ=73.40232°±0.0.07789°, μαcosδ=3.07±0.90mas/yr, μδ=4.65±0.90mas/yr, 15', 7 members. The incidence of the proper motion errors in the determination of the cluster parameters and of the stellar membership is analysed and it is found that they do not significantly change. We finally compare the astrometric members with the photometric ones given in the literature.
摘要:The Scandinavian Bronze Age started quite rapidly at around 1750 BC, and is marked by three simultaneous events: 1) importation of bronze from the east Mediterranean region, 2) export of amber from southeast Sweden to the east Mediterranean region, and 3) the carving of pictures of big ships on bedrock and boulders in southern Scandinavia. We take this as evidence of travel and trading by people coming from the east Mediterranean region on big ships via Gibraltar and the North Sea to Scandinavia. At the same time, the Sun cult flourished in southern Sweden and Denmark, as evidenced by monuments perfectly oriented with respect to the Sun’s daily and annual motions over the sky (e.g. Ales Stones), rock carvings of solar symbols and in solar alignment, and a number of ritual objects related to the Sun Cult (e.g. The Golden Sky Dome). In this paper, we summarize and update available data, especially the data from Southern Sweden.
摘要:The Earth-Moon system has often been characterized as having some characteristics of a “double planet” system. It is demonstrated that while the orbital barycenter of the Earth-Moon pair lies inside the radius of the Earth, the Moon does meet all three requirements of the IAU definition for “planet” and therefore the Moon can correctly be identified as the Solar System’s 9th planet. In order to avoid confusion by this development it is necessary to add definitions for “double planet”, “double dwarf planet”, “satellite planet”, and “satellite” to complement the International Astronomical Union definitions for “planet” and “dwarf planet”. The Earth-Moon system meets the requirements of a “double planet” system while the Pluto-Charon system meets the requirements of a “double dwarf planet” system. In order to extrapolate sub-stellar taxonomy to exoplanetary systems, general formation mechanisms (star-like gas collapse in molecular clouds vs. proto-planetary disk formation) should be included in the definitions for the various classes of sub-stellar mass bodies.
摘要:Ionosphere parameters determination is used to characterize its composition in particles. These results have been compared to data curried from Ouagadougou station. The present study deals with Total Electron Contents (TEC) results determined by Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) version 1.94 and International Reference Ionosphere (IRI) version 2012 during solar cycle 22. The minimum and maximum phases of solar cycle 22 are considered in this study for TEC determination. The station is located at Ouagadougou, in western Africa, characterized by its latitude (12.4°N) and longitude (358.5°E). The present study completes the two previous articles on hmF2 and foF2 parameters determination on the same station by comparison between TEC results carried out from TIEGCM and IRI models. So that, quiet time condition is determined by Aa (≤20 nT) for the five quietest days in each characteristic month of seasons. Rz values characterize minimum and maximum solar cycle phases.
摘要:The metrics of the compact objects should be the continuous function of coordinates. The metrics inside every object is set by its internal structure. The metrics in the adjacent empty space is described by the outer Schwarzschild or Kerr solution of the Einstein field equations. It appears that the linkup of both object-interior and empty-space metrics is not continuous at the physical surfaces of the objects for the common, generally (by convention) accepted set of assumptions. We suggest the new way of how to achieve the success in the linkup, which does not assume the higher value of the relativistic speed limit in the empty space governed by the object, in contrast to our previous suggestion. We also give a more detailed explanation of the existence of inner physical surface of compact objects and suggest the way of the linkup of metrics in this surface. To achieve the continuous linkup, we assume a lower value of the speed limit in the object’s interior as well as a new gauging of the outer Schwarzschild solution for the inner empty space of the object. Newly established gauging constants are calculated and the success of the linkup is shown in several examples. The new gauging implies a lower gravitational attraction (lower gravitational constant) in the inner empty space in comparison with that in the outer space, which is measured in the common, observed, gravitational interactions of material objects.
摘要:The present paper gives a theoretical model for the change in entropy of spinning black holes due to change in mass to use the first law of black hole mechanics for unit spinning parameter and angular momentum in XRBs. This shows that the entropy change with respect to the mass of uncharged spinning black holes is essentially the function of mass and their surface gravity are lesser than to that of the non-spinning black holes.
摘要:According to general relativity the geometry of space depends on the distribution of matter or energy fields. The relation between the local geometrical parameters and the volume enclosed in given limits varies with the distribution of matter. Thus properties like particle number, mass or energy density, defined in the Euclidean tangent space, cannot be integrated to give conserved integral data like total number, mass or energy. To obtain integral conservation, a correction term must be added to account for the curvature of space. For energy this correction term is the equivalent of potential energy in Newtonian gravitation. With this correction the formation of black holes in the sense of singularities by gravitational collapse does no longer occur and the so called dark energy finds its natural explanation as potential energy of matter itself.
摘要:The coronal mass ejections (CMEs) produce by Sun poloidal magnetic fields contribute to geomagnetic storms. The geomagnetic storm effects produced by one-day-shock, two-days-shock and three-days-shock activities on Ouagadougou station F2 layer critical frequency time variation are analyzed. It is found that during the solar minimum and the increasing phases, the shock activity produces both positive and negative storms. The positive storm is observed during daytime. At the solar maximum and the decreasing phases only the positive storm is produced. At the solar minimum there is no three-days-shock activity. During the solar increasing phase the highest amplitude of the storm effect is due to the one-day-shock activity and the lowest is produced by the two-days-shock activity. At the solar maximum phase the ionosphere electric current system is not affected by the shock activity. Nevertheless, the highest amplitude of the storm effect is caused by the two-days-shock activity and the lowest by the one-day-shock activity. During the solar decreasing phase, the highest amplitude provoked by the storm is due to the three-days-shock activity and the lowest by the one-day-shock activity.
摘要:The mass limit of neutron star has still remained a mystery. The existing Tolman-Oppenheimer-Volkoff (TOV) equation for calculating the limit always gives different values, by introducing different assumptions and having been predicted like 0.7 Mo, 3.2 Mo, 3.6 Mo, where Mo = 1.98 × 1030 Kg. There is a need of some better technique to adopt other than TOV relation to seek out the value. In this paper, a new relation between the mass of the collapsing star and its average density ρ′ has been derived and used to calculate the limit of neutron star. The conditions in radii between Schwarz Child’s radius and the actual radius of the collapsing star have been introduced to calculate the mass of star above which it will transform into a black hole and below it to a neutron star. A new constant, JN = 8.53707554 × 1039 N-3/2s-3Kg3 has been proposed with which if we introduce the average density of the collapsing neutron star, its mass limit can be calculated very easily. By putting the most possible mass density, which is the minimum required density for a collapsing star to transform into the black hole, it has been found that the mass limit of neutron star is quite higher than it has been assumed. The definition for black hole has also been re-defined on the basis of said radii conditions.
摘要:A central interaction of bodies which at short distances is stronger than Newtonian is considered. It is shown that the escape velocity from a body is essentially more than the escape velocity given by Newton’s theory. The connection of the new central interaction with the gravitational radius of a black hole is found. It is shown that the gravitational radius of a black hole may be arbitrarily large.
摘要:In order to model the Fermi bubbles we apply the theory of the superbubble (SB). A thermal model and a self-gravitating model are reviewed. We introduce a third model based on the momentum conservation of a thin layer which propagates in a medium with an inverse square dependence for the density. A comparison has been made between the sections of the three models and the section of an observed map of the Fermi bubbles. An analytical law for the SB expansion as a function of the time and polar angle is deduced. We derive a new analytical result for the image formation of the Fermi bubbles in an elliptical framework.
摘要:The optimizing total velocity increment Δv needed for orbital maneuver between two elliptic orbits with plane change is investigated. Two-impulse orbital transfer is used based on a changing of transfer velocities concept due to the changing in the energy. The transferring has been made between two elliptic orbits having a common centre of attraction with changing in their planes in standard Hohmann transfer with the terminal orbit which is elliptic orbit and not circular. We develop a treatment based on the elements of elliptic orbits a1,e1, a2,e2, and?aT,eT of the initial orbit, final orbit and transferred orbit respectively. The first impulse Δv1 at the perigee induces a rotation of the orbital plane by ?which will be minimized. The second impulse Δv2 at apogee is induced an angle ?to product the final elliptic orbit. The total plane change required . We calculate the total impulse Δv and minimize by optimizing angle of plane’s variation . We obtain a polynomial equation of six degrees on the two transfer angles between neither two elliptic orbits ?and . The solution obtained numerically, using programming code of MATHEMATICA V10, with no condition on the eccentricity or the semi-major axis of the initial, transformed, and the final orbits. We find that there are constrains on the transfer angles and α. For αit must be between 40°and 160°, and there is no solution if αis less than 40°and bigger than 160°and ?takes the values less than 40°. The minimum total velocity increments obtained at the value of ?less than 25°and& alpha;equal to 160°. This is an interesting result in orbital transfer problem in which the change of orbital plane is necessary for the transferring.
摘要:It is shown that in order that the fluid pressure and acceleration are uniform and finite in Einstein’s Static Universe (ESU), , the cosmological constant, is zero. being a fundamental constant, should be same everywhere including the Friedman model. Independent proofs show that it must be so. Accordingly, the supposed acceleration of the universe and the attendant concept of “Dark Energy”(DE) could be an illusion;an artifact of explaining cosmological observations in terms of an oversimplified model which is fundamentally inappropriate. Indeed observations show that the actual universe is lumpy and inhomogeneous at the largest scales. Further in order that there is no preferred centre, such inhomogeneity might be expressed in terms of infinite hierarchial fractals. Also, the recent finding that the Friedman model intrinsically corresponds to zero pressure (and hence zero temperature) in accordance with the fact that an ideal Hubble flow implies no collision, no randomness (Mitra, Astrophys. Sp. Sc., 333,351, 2011) too shows that the Friedman model cannot represent the real universe having pressure, temperature and radiation. Dark Energy might also be an artifact of the neglect of dust absorption of distant Type 1a supernovae coupled with likely evolution of supernovae luminosities or imprecise calibration of cosmic distance ladders or other systemetic errors (White, Rep. Prog. Phys., 70, 883, 2007). In reality, observations may not rule out an inhomogeneous static universe (Ellis, Gen. Rel. Grav. 9, 87, 1978).
摘要:The present paper deals with the existence of periodic orbits in the Circular Restricted Four-Body Problem (CR4BP) in two-dimensional co-ordinate system when the second primary is a triaxial rigid body and the third primary of inferior mass (in comparison of the other primaries) is placed at triangular libration point L4 of the Circular Restricted Three-Body Problem (CR3BP). With the help of generating solutions, we formed a basis for the existence of periodic orbits, then an analytical approach given by Hassan et al. [1], was applied to our model of equilateral triangular configuration. It is found that in general solution also;the character of periodic orbits is conserved. For verification of the existence of periodic orbits, we have applied the criterion of Duboshin [2] and found satisfied.
摘要:The original online version of this article (Bjarne Lorenzen (2017) The Cause of the Allais Effect Solved. Volume 7, 69-90 doi: 10.4236/ijaa.2017.72007) unfortunately contains several mistakes.
天文学与天体物理学国际期刊(英文)的期刊信息
创刊时间:2011
地区:CN
语言:中文
热门主题:COSMOLOGY
UNIVERSE
DARK
GRAVITATIONAL
GALAXIES
STARS
RELATIVITY
SOLAR
COSMIC
GRAVITY