共查询到20条相似文献，搜索用时 65 毫秒
1.
In the theory of supergravity (N=1), the supersymmetric version of general relativity, and for the Kasner cosmological model (Bianchi type I) we find a non-trivial solution (for the metric and spinor-vector) under the most simple assumption =11 + 22; 12+21=0 and for a special choosed gaugeN=1,N
j=0, 0=0. This method could be also applied to other cosmological metrics and extended to enlarged Grassmann basis.O. Obregón was partially supported by the Alexander von Humboldt Stiftung. 相似文献
2.
Kathleen Connor Howell 《Celestial Mechanics and Dynamical Astronomy》1984,32(1):53-71
A largely numerical study was made of families of three-dimensional, periodic, halo orbits near the collinear libration points in the restricted three-body problem. Families extend from each of the libration points to the nearest primary. They appear to exist for all values of the mass ratio , from 0 to 1. More importantly, most of the families contain a range of stable orbits. Only near L1, the libration point between the two primaries, are there no stable orbits for certain values of . In that case the stable range decreases with increasing , until it disappears at =0.0573. Near the other libration points, stable orbits exist for all mass ratios investigated between 0 and 1. In addition, the orbits increase in size with increasing . 相似文献
3.
The coefficients A
0 of the limb-darkening functions I()/I
center=P
5()=A
ii (i=0,...5, =cos), published by Neckel and Labs (1994), and the corresponding disk-center intensities I
center=I(=1), which were taken from the absolutely calibrated Kitt Peak FTS Atlas of the disk center (Brault et al., see Neckel and Labs, 1984, and Neckel 1999), are used to derive `limb intensities' I
limb=I(=0)=A
0
I
center. The corresponding `limb temperatures' T
limb vary only slightly with wavelength; the mean value (4750 K) and the wavelength of maximum intensity (605 nm) conform to Wien's law (max
T=0.288 cm K). Further, T
limb agrees closely with that temperature, which follows from Avrett's (2000) model of the photosphere for 5000.006; for this layer the optical thickness along the line of sight is close to 1 (`the limb'; compare Unsöld, 1968). The slight variation of T
limb with wavelength is presumably due to systematic errors in the Neckel and Labs intensity data: it corresponds almost precisely to the differences between their data and the more recent ones provided by, e.g., Burlov-Vasiljev, Gurtovenko, and Matvejev (1995), and Burlov-Vasiljev, Matvejev, and Vasiljeva (1998). Two simple correction functions (for 550 nm and 550 nm) are proposed, which apply to all Neckel and Labs intensity data (disk center and full disk, line spectrum and (quasi) continuum), and to the absolutely calibrated Kitt-Peak FTS Atlas (spectra of disk center and full disk) as well. 相似文献
4.
A. M. I. Osman 《Astrophysics and Space Science》1985,116(2):299-311
Surface photometry of the UV continuum galaxy NGC 838 has been carried out in theB, V system using photographic plates obtained with the 74 Kottamia telescope, Egypt. Isophotes, luminosity profiles, integrated photographic magnitudes, effective diameters and other photometric parameters are derived.The photoelectrically calibrated total apparent magnitudes areB
T
=13.57 with maximum diameters 1.57×1.34 (at threshold
m
=27.7 mag.//) andV
T
=12.91 with maximum diameters 1.54×1.32 (at threshold
m
=27.7 mag./). The integrated colour index(B–V)
T
=0.66 and the effective surface brightness
e
(B=19.0 mag./) and
e
(V=19.7 mag./. The major axis is at position angle =85°±1°.The nucleus of NGC 838 is quite blue (integrated colour(B–V)=0.41 forr
*<0.1) compared to normal galaxies while the colour becomes redder from the nucleus outwards. The UV excess, H emission and radio continuum emission previously observed from this galaxy by other investigators may be attributed to a recent burst of star formation in the nucleus of the galaxy of duration slightly greater than 2×107 yr. 相似文献
5.
Cornelis Zwaan 《Solar physics》1974,37(1):99-111
The sunspot models published so far do not reproduce the observed run of the umbral continuum intensities over the entire spectral range 0.5 < < 4 m. Moreover, in several previous models is the temperature gradient smaller than both the adiabatic and the radiative equilibrium gradient.Agreement between intensities computed from acceptable models and measured intensities can be obtained by introducing an additional opacity for 0.8 m, which is probably caused by the crowding of atomic and molecular lines. We present a new umbral model atmosphere with a wavelength dependent opacity enhancement factor which explains the continuum intensities and also reproduces plausible center-to-limb variations and line profiles. This model is in radiative equilibrium down to 0.5 = 1.5, with an effective temperature of 4000 ± 100K. For the deeper superadiabatic layers a small but probably significant departure from radiative equilibrium is indicated by the intensities in the range 1.5 < < 2.4 m.The uncertainties in the present model and the effect of the additional opacity on line profiles are briefly discussed. 相似文献
6.
A comparison is made between the stability criteria of Hill and that of Laplace to determine the stability of outer planetary orbits encircling binary stars. The restricted, analytically determined results of Hill's method by Szebehely and co-workers and the general, numerically integrated results of Laplace's method by Graziani and Black are compared for varying values of the mass parameter =m
2/(m
1+m
2). For 00.15, the closest orbit (lower limit of radius) an outer planet in a binary system can have and still remain stable is determined by Hill's stability criterion. For >0.15, the critical radius is determined by Laplace's stability criterion. It appears that the Graziani-Black stability criterion describes the critical orbit within a few percent for all values of . 相似文献
7.
S. Al-Mufti A. H. Olavesen F. Hoyle N. C. Wickramasinghe 《Astrophysics and Space Science》1982,84(1):259-261
Unidentified interstellar absorption bands at =3.2 m and 3.3 m might be due to amino-acids in bacterial grains. 相似文献
8.
C. A. Lindsey 《Solar physics》1977,52(2):263-281
Infrared continuum observations of the Sun at wavelengths between 10 and 30 show a nonisothermal response of the upper photosphere to compression waves associated with the five-minute oscillations. Observations were made with four broad-band filters with effective transmission wavelengths between 10 and 26 and with a 10 aperture. Further observations at submillimeter wavelengths with a 2 aperture did not resolve oscillatory fluctuations of five-minute period.Comparisons with velocity field data of Howard (1976) suggest that the relaxation time of the photosphere exceeds (300/2) seconds at the height of formation of the 26 continuum (5000Å 10-2). The photosphere reponds to 3 mHz oscillatory motion with considerably less compression than expected for simple acoustic modes in an adiabatically responsive atmosphere, confirming the evanescent character of the five-minute oscillations. 相似文献
9.
K. T. Alfriend 《Celestial Mechanics and Dynamical Astronomy》1971,4(1):60-77
The stability ofL
4 and the motion aboutL
4 in the restricted problem of three bodies is investigated when there is three-to-one commensurability between the long and short periods of motion, that is, when the mass ratio has the value =0.013516.... The two time scale method is used (1) to show thatL
4 is an unstable equilibrium point when =3, (2) to determine for what initial conditions periodic orbits occur when 3, (3) to determine the stability of the periodic orbits, and (4) to investigate the boundedness of the motions aboutL
4 when 3. 相似文献
10.
Osman Demircan 《Astrophysics and Space Science》1979,62(1):189-201
The aim of the present paper will be to present a new approach to the light changes of eclipsing binary systems. The light changes have been expanded into the Fourier-Bessel and Dini series. The coefficients of these expansions which are the Hankel transforms of the order of the loss of light (1–l) have been expressed in terms of the eclipse elements. These discrete Hankel transformsH
(j
m
) andH
(
m
) valid for only the positive real zerosj
m
and
m
of the functionsJ
and [xJ(x)+J
(x)] have been generalized for any positive value of andy. Thus, these general expressions for the Hankel transforms of the light curves which are valid for all types of eclipses, for any arbitrary degree of the adopted limb-darkening law and, moreover, for any positive value of the free parameters andy, may be used for the solution of the elements of eclipsing binary systems. 相似文献
11.
Jaume Llibre 《Celestial Mechanics and Dynamical Astronomy》1982,28(1-2):83-105
We study some aspects of the restricted three-body problem when the mass parameter is sufficiently small. First, we describe the global flow of the two-body rotating problem, =0, and we use it for the analysis of the collision and parabolic orbits when 0. Also we show that for any fixed value of the Jacobian constant and for any >0, there exists a 0>0 such that if the mass parameter [0,0], then the set of bounded orbits which are not contained in the closure of the set of symmetric periodic orbits has Lebesgue measure less than .Paper presented at the 1981 Oberwolfach Conference on Mathematical Methods in Celestial Mechanics. 相似文献
12.
An essential part in the mechanics under study is taking into consideration the effect of motions of the Universe objects upon that of an individual one surrounded by them including those infinitely far from it. Only macro-objects of the Universe are meant here.
Zusammenfassung Ein wesentlicher Bestandteil der Mechanik unter unserer Betrachtung ist die Berechnung des Einflusses auf die Bewegung eines individuellen Objektes von Bewegungen der Universum Objekte die es umringen einschließlich jene Objekte, die unendlich entfernt sind. Nur Makroobjekte des Weltalles sind in der Absicht dabei.
, . .相似文献
13.
From an analysis of the interstellar extinction we conclude that interstellar grains are of three main kinds: graphite spheres of radii 0.02 m making up 10% of the total grain mass, small dielectric spheres of radius about 0.04 m making up 25% of the mass, and hollow dielectric cylinders containing metallic iron with diameters of 2/3 m making up 45% of the mass. The remaining 20% consists of other metals and metal oxides. The main dielectric component of the grains appears to be comprised of organic material. 相似文献
14.
We show that a 3 extinction feature in galactic infrared sources cannot be due to water-ice grains. Infrared spectra with a resolution of /=0.015 are in remarkably close agreement with the 2.5–4 extinction properties calculated for bacterial grains. 相似文献
15.
Conditions prevalent in dense molecular clouds are shown to favour the polymerization of H2CO molecules and the deposition of formaldehyde co-polymer mantles, with typical radii 10–5 cm, on smaller refractory grains. If a significant fraction of such co-polymer coated grains are expelled with systematic gas flows into the general interstellar medium, these moderately refractory grains may be responsible for the bulk of interstellar extinction and polarization at optical wavelengths. Mie calculations for a mixture consisting of iron, graphite and POM particles are presented as an example where POM grains of radii 0.15 dominate the extinction at optical wavelengths, providing a satisfactory overall fit to a range of extinction data. A size distribution of POM needles with a mean radius 0.15 also provides good agreement with data on interstellar linear as well as circular polarization. Suitably end-capped and stabilized co-polymer-coated grains, with either silicate or graphite cores, may survive at temperatures 450 K under interstellar ambient conditions and be responsible for the 10 emission feature in many sources. Theoretically computed band profiles of the 10 -feature in POM coated grains, in general, provide better agreement with observations than most types of silicate grains considered so far. We also note that an unexplained dip at 10 in the 8–12 feature of the infrared source OH 231.8+4.2 may be a signature of POM grains; likewise, a persistent 3.3 emission feature in many different types of infrared source could be attributed to the CH stretching mode in formaldehyde co-polymer grains. 相似文献
16.
M. A. Forman 《Astrophysics and Space Science》1977,49(1):83-97
The concept of velocity correlation functions is introduced and applied to the calculation of cosmic ray spatial diffusion coefficients. It is assumed that the pitch angle scattering coefficient is already known from some other theory, and is reasonably well-behaved. Previous results for the coefficient for diffusion parallel to the mean field are recovered when the velocity-changing mechanism is artificially restricted to pitch angle scattering. The velocity correlation method is then applied to the more general case where there are fluctuations in the local mean field. It is found that the parallel diffusion coefficient is reduced in proportion to the amplitude of the field fluctuations, and that the ratio of the perpendicular to parallel diffusion coefficients cannot be greater than B
x
2
/B
0
2
. It is shown in the appendix that the Liouville form of the scattering equation implies that the Fokker-Planck coefficients
2/t=2D
and /t=D
/, and that all higher-order coefficients are identically zero. 相似文献
17.
A. Altamore F. Smriglio E. Bussoletti C. E. Corsi L. Rossi 《Astrophysics and Space Science》1980,72(1):159-165
A comparison between theGeneral Catalogue of Cool Carbon Stars (CCS) and theAFGL Catalogue has been performed.Eighty-five stars have been found in common between the two lists. Eighty-four stars which were present in Baumert's comparison between CCS and the 2 Sky Survey have no counterpart in the AFGL. Four new tentative identifications are given. The analysis of the two colours diagrams K-[4.2 ] vs. I-K and I-[4.2 ] vs. [4.2 ]-[11 ] led to the conclusion that all the infrared emission from the sources seems to come from a single circumstellar shell. 相似文献
18.
Since there are reasons for expecting supersymmetry in an underlying quantum theory of gravity, one is led to study quantum and classical cosmology with supergravity. In particular, classical solutions corresponding to these models could also be used to generate the quantization of supersymmetric minisuperspaces. In generating these solutions, the solution to the Rarita-Schwinger field in the cosmological background is also obtained. In this paper the supercosmological equations of Einstein-Rarita-Schwinger are solved for the micro-superspace sector of the Taub model, under the assumption =11*22 and
. The solution for the parameters of the metric and are proportional to each other in each order, the zeroth-order and also the second-order terms. The zeroth-order terms correspond to the solution in general relativity and are logarithmic in time, the 12 terms have an hyperbolic time-dependence. The Rarita-Schwinger field has the form cos((2/D
3)ln |t–t
0|) and oscillates an infinite number of times astt
0. This oscillating behaviour of the solution for is not only present when spinor fields are treated in a curved background, but also some cosmological wave functions behave in this manner. This solution is at the same time the supercosmological solution for the microsuperspace sector of the Taub model and also the Rarita-Schwinger field in this background.This work was supported in part by CONACYT grant P228CCOX891723, and DGICSA SEP grant C90-03-0347. 相似文献
19.
A numerical simulation of energetic particle motion in the interplanetary medium is carried out using HEOS-2 magnetometer data in order to computeD(), the pitch angle diffusion coefficient, where is cosine of pitch angle defined with respect to the local field. WhileD() exceeds that given by quasi-linear theory near 90° pitch angle, it is significantly less at higher values of , leading to a parallel transport coefficient in good accord with that given by experimental studies of solar proton propagation. In particular, =0.031 AU at a particle magnetic rigidity of 455 MV, while experimental results range from 0.05 to 0.07 AU (+100%, –50%) in this rigidity region. Furthermore, observed approximately -dependent solar proton pitch angle distributions are consistent with the computed findingD()/(1 –
2)2 ~ constant.The validity of various analytical corrections to quasi-linear theory as 0 are also investigated numerically. 相似文献
20.
, , , . () , . , . 相似文献