共查询到20条相似文献，搜索用时 31 毫秒
1.
Richard L. Branham Jr. 《Celestial Mechanics and Dynamical Astronomy》1986,39(3):239-247
A method is given, based on the pseudoinverse of the equations of condition, to obtain error estimates for the solution in the normL
1 of an over-determined linear system. The computational labor to obtain the errors, while not trivial, is less than that for various competing methods, particularly if there are many more equations of condition than unknowns. The error estimates for anL
1 solution are substantially larger than those for a least squares solution of the some data. It is suggested that a complete discussion of a linear system include at least bothL
1 and least squares solutions with their respective errors and the condition number of the linear system. 相似文献
2.
Dieter Lorenz-Petzold 《Astrophysics and Space Science》1985,115(1):197-198
The inhomogeneous Bianchi type-VI0 perfect fluid solution given recently by Roy and Narain (1985) is shown to be identical with the solution first given by Tomita (1978). 相似文献
3.
Edelman Colette 《Celestial Mechanics and Dynamical Astronomy》1993,55(4):369-386
The newtonian problem ofn mass points bodies is invariant by several changes of spatio-temporal variables. These symmetries correspond to arbitrary choices of the referential and they are related via Noether's theorem or by its generalization to conservative quantities of the motion. Forn=2 the author has defined two families of symmetriesS 1 andS 2 changing the eccentricity of a solution. The family of symmetries,S 1, is associated to the arbitrary choice of thezero level of the potential and may related unbounded and bounded solutions. The family of symmetries,S 2, is related to a possibleaffinity of the configurations space. Via a symmetry of theS 2 family a zero angular momentum solution is equivalent to a non-zero angular momentum solution. Via a product of two symmetries of each family, denoted byS 1.S 2, any solution of the two-body problem is equivalent to a circular solution. In this paper it is shown that some of these transformations may be generalized to symmetries changing the quantityC 2 H in then-body problem, whereC is the angular momentum andH is the energy. The extension is easily made to central solutions of then-body problem because involving several synchroneous two-body problems. We consider for exposition then=3 case. The principal results may be resumed by the following propositions:
- The two families of symmetriesS 1 andS 2 are described by a spatial transformation product of an instantaneous homothethy and an instantaneous rotation completed by a change of temporal variable.
- TheS 1 family of symmetries may relate unbounded and bounded central solutions of the same type, i.e. unaligned or aligned.
- TheS 2 family of symmetries may regularize multiple collisions among central solutions of the same type.
4.
D. J. Jezewski 《Celestial Mechanics and Dynamical Astronomy》1983,30(4):343-361
The motion of a satellite subject to an inverse-square gravitational force of attraction and a perturbation due to the Earth's oblateness as theJ 2 term is analyzed, and a uniform, analytic solution correct to first-order inJ 2, is obtained using a noncanonical approach. The basis for the solution is the transformation and uncoupling of the differential equations for the model. The resulting solution is expressed in terms of elementary functions of the independent variable (the ‘true anomaly’), and is of a compact and simple form. Numerical results are comparable to existing solutions. 相似文献
5.
Albert P. Linnell 《Astrophysics and Space Science》1973,22(1):13-43
Computer routines permit the solution of eclipsing binary light curves on the Russell Model. With additional automatic point plot routines, the operator has available all necessary supervisory control for an optimum solution. A solution of a synthetic light curve, whose parameters simulate those calculated for the physical system, is an important adjunct to test convergence properties of the physical system solution.Application to EE Peg determines values ofx
x
andx
x
even though secondary minimum is only 0.08 mag. deep. First order perturbation theory is used with the Russell Model to calculate a final triaxial ellipsoid model.Solution of the CM Lac light curve shows that the data require an occultation eclipse at primary minimum, in contrast to the available nomographic solution. The point plot routines demonstrate a substantial improvement effected by the computer solution and show that the latter technique can determine limb darkening coefficients in this partially-eclipsing system.Originally presented at the IAU Colloquium No. 16 held at the University of Pennsylvania, Philadelphia, U.S.A., September 8–11, 1971. 相似文献
6.
Luigi De Cesare 《Astrophysics and Space Science》1973,25(1):133-148
For an evaluation of the superconducting critical fieldH
c as a function of the mass-density in the external layers of cold magnetic white dwarfs and in the superconducting proton fluid in neutron stars, we use the solution of a differential equation involvingH
c as a function of the pressure. The differential equation and its solution are obtained by pure thermodynamic way.Finally other thermodynamic quantities are calculated for the above superconducting astrophysical systems. 相似文献
7.
We present an exact solution of the Brans-Dicke equations for cosmological models of Bianchi type VI0 with stiff matter. The solution represents anisotropic universe which has its analogy in Einstein's theory. The corresponding result for a plane symmetry Bianchi type I model is obtained as a special case. 相似文献
8.
Neeraj Pant 《Astrophysics and Space Science》2011,331(2):633-644
We present three new categories of exact and spherically symmetric Solutions with finite central parameters of the general
relativistic field equations. Two well behaved solutions in curvature coordinates first category are being studied extensively.
These solutions describe perfect fluid balls with positively finite central pressure, positively finite central density; their
ratio is less than one and causality condition is obeyed at the centre. The outmarch of pressure, density, pressure-density
ratio and the adiabatic speed of sound is monotonically decreasing for these solutions. Keeping in view of well behaved nature
of these solutions, one of the solution (I1) is studied extensively. The solution (I1) gives us wide range of Schwarzschild parameter u (0.138≤u≤0.263), for which the solution is well behaved hence, suitable for modeling of Neutron star. For this solution the mass of
Neutron star is maximized with all degree of suitability and by assuming the surface density ρ
b
=2×1014 g/cm3. Corresponding to u=0.263, the maximum mass of Neutron star comes out to be 3.369 M
Θ with linear dimension 37.77 km and central and surface redshifts are 4.858 and 0.4524 respectively. We also study some well
known regular solutions (T-4, D-1, D-2, H, A, P) of Einstein’s field equations in curvature coordinates with the feature of
constant adiabatic sound speed. We have chosen those values of Schwarzschild parameter u for which, these solutions describe perfect fluid balls realistic equations of state. However, except (P) solution, all these
solutions have monotonically non-decreasing feature of adiabatic sound speed. Hence (P) solution is having a well behaved
model for uniform radial motion of sound. Keeping in view of well behaved nature of the solution for this feature and assuming
the surface density; ρ
b
=2×1014 g/cm3, the maximum mass of Neutron star comes out to be 1.34 M
Θ with linear dimension 28.74 km. Corresponding central and surface redshifts are 1.002 and 0.1752 respectively. 相似文献
9.
We present a new spherically symmetric solution of the general relativistic field equations in isotropic coordinates. The
solution is having positive finite central pressure and positive finite central density. The ratio of pressure and density
is less than one and casualty condition is obeyed at the centre. Further, the outmarch of pressure, density and pressure-density
ratio, and the ratio of sound speed to light is monotonically decreasing. The solution is well behaved for all the values
of u lying in the range 0<u≤.186. The central red shift and surface red shift are positive and monotonically decreasing. Further, we have constructed
a neutron star model with all degree of suitability and by assuming the surface density ρ
b
=2×1014 g/cm3. The maximum mass of the Neutron star comes out to be M=1.591 M
Θ with radius R
b
≈12.685 km. The most striking feature of the solution is that the solution not only well behaved but also having one of the
simplest expressions so far known well behaved solutions. Moreover, the good matching of our results for Vela pulsars show
the robustness of our model. 相似文献
10.
W. Thuillot 《Celestial Mechanics and Dynamical Astronomy》1984,34(1-4):245-253
The construction of an analytical theory of the motion of the Galilean satellites of Jupiter requires that we keep track of the dynamical parameters, that is, the masses of the satellites, and the harmonic coefficients of the potential of the planet J2 and J4. This is realized here. But as in other theories the solution becomes partly numerical from the resolution of an autonomous system. The aim of this paper is to present a method to obtain developped solutions of this autonomous system. In these solutions the proper motions of the pericenters and nodes are obtained as short series developped in the neighbourhood of a numerical solution. We have used these results to obtain complementary terms in the general solution which give a complete representation of the motions with respect to the dynamical parameters. 相似文献
11.
Shri Ram 《Astrophysics and Space Science》1984,104(1):151-155
An exact solution of Einstein's equations corresponding to the conformally invariant scalar field with tracefree energy-momentum tensor as source is obtained in Bianchi type VI0 class of metrics. The solution represents a spatially homogeneous but anisotropy universe which admits anisotropic expansions. Some properties of the cosmological model are discussed. 相似文献
12.
A. V. Usmanov 《Solar physics》1993,143(2):345-363
An attempt is made to infer parameters of the solar corona and the solar wind by means of a numerical, self-consistent MHD simulation. Boundary conditions for the magnetic field are given from the observations of the large-scale magnetic field at the Sun. A two-region, planar (the ecliptic plane is assumed) model for the solar wind flow is considered. Region I of transonic flow is assumed to cover the distances from the solar surface up to 10R
S (R
S is the radius of the Sun). Region II of supersonic, super-Alfvénic flow extends between 10R
S and the Earth's orbit. Treatment for region I is that for a mixed initial-boundary value problem. The solution procedure is similar to that discussed by Endler (1971) and Steinolfson, Suess, and Wu (1982): a steady-state solution is sought as a relaxation to the dynamic equilibrium of an initial state. To obtain a solution to the initial value problem in region II with the initial distribution of dependent variables at 10R
S (deduced from the solution for region I), a numerical scheme similar to that used by Pizzo (1978, 1982) is applied. Solar rotation is taken into account for region II; hence, the interaction between fast and slow solar wind streams is self-consistently treated. As a test example for the proposed formulation and numerical technique, a solution for the problem similar to that discussed by Steinolfson, Suess, and Wu (1982) is obtained. To demonstrate the applicability of our scheme to experimental data, solar magnetic field observations at Stanford University for Carrington rotation 1682 are used to prescribe boundary conditions for the magnetic field at the solar surface. The steady-state solution appropriate for the given boundary conditions was obtained for region I and then traced to the Earth's orbit through region II. We compare the calculated and spacecraft-observed solar wind velocity, radial magnetic field, and number density and find that general trends during the solar rotation are reproduced fairly well although the magnitudes of the density in comparison are vastly different. 相似文献
13.
A. N. Cox recently showed that a 20% opacity decrease in the 20,000-30,000 K region as indicated by the new Livermore OPAL opacities reconciles the discrepancy between pulsation and evolution masses of double-mode RR Lyrae variables. Nonlinear hydrodynamic calculations were performed for RR Lyrae models of mass 0.75M
, 51L
, andZ = 0.0001 (Osterhoff II type) including this opacity decrease. The Stellingwerf periodic relaxation method was used to converge the models to a limit cycle, and the Floquet matrix eigenvalues calculated to search for a tendency of the fundamental mode to grow from the full-amplitude overtone solution, and the overtone mode to grow from the full-amplitude fundamental solution, thereby predicting double-mode behavior. Models ofT
eff < 7000 K with the opacity decrease have positive fundamental-mode growth rates in the overtone solution, in contrast to earlier results by Hodson and Cox (1982), and models withT
eff > 7000 have positive 1st overtone growth rates in the fundamental-mode solution, but double-mode behavior was not found. 相似文献
14.
We present a well behaved class of Charge Analogue of Heintzmann (Z. Phys. 228:489, 1969) solution. This solution describes charge fluid balls with positively finite central pressure and positively finite central
density ; their ratio is less than one and causality condition is obeyed at the centre. The outmarch of pressure, density,
pressure-density ratio and the adiabatic speed of sound is monotonically decreasing, however, the electric intensity is monotonically
increasing in nature. The solution gives us wide range of constant K (1.25≤K≤15) for which the solution is well behaved and therefore, suitable for modeling of super dense star. For this solution the
mass of a star is maximized with all degrees of suitability and by assuming the surface density ρ
b
=2×1014 g/cm3. Corresponding to K=1.25 and X=0.42, the maximum mass of the star comes out to be 3.64M
Θ with linear dimension 24.31 km and central redshift 1.5316. 相似文献
15.
We present a well behaved class of charged analogue of M.C. Durgapal (J. Phys. A, Math. Gen. 15:2637, 1982) solution. This solution describes charged fluid balls with positively finite central pressure, positively finite central density; their ratio is less than one and causality condition is obeyed at the centre. The outmarch of pressure, density, pressure-density ratio and the adiabatic speed of sound is monotonically decreasing, however, the electric intensity is monotonically increasing in nature. This solution gives us wide range of parameter for every positive value of n for which the solution is well behaved hence, suitable for modeling of super dense stars. Keeping in view of well behaved nature of this solution, one new class of solution is being studied extensively. Moreover, this class of solution gives us wide range of constant K (0≤K≤2.2) for which the solution is well behaved hence, suitable for modeling of super dense stars like strange quark stars, neutron stars and pulsars. For this class of solution the mass of a star is maximized with all degree of suitability, compatible with quark stars, neutron stars and pulsars. By assuming the surface density ρ b =2×1014 g/cm3 (like, Brecher and Capocaso, Nature 259:377, 1976), corresponding to K=0 with X=0..235, the resulting well behaved model has the mass M=4.03M Θ , radius r b =19.53 km and moment of inertia I=1.213×1046 g?cm2; for K=1.5 with X=0.235, the resulting well behaved model has the mass M=4.43M Θ , radius r b =18.04 km and moment of inertia I=1.136×1046 g?cm2; for K=2.2 with X=0.235, the resulting well behaved model has the mass M=4.56M Θ , radius r b =17.30 km and moment of inertia I=1.076×1046 g?cm2. These values of masses and moment of inertia are found to be consistent with the crab pulsars. 相似文献
16.
17.
Gamal G. L. Nashed 《Astrophysics and Space Science》2014,350(2):791-797
Spherically symmetric tetrad field is applied to the field equation of modified teleparallel gravity theory. Some constraints are assumed on the resulting non-linear partial differential equations. Exact vacuum solution is derived with two constants of integration. The derived solution has a vanishing scalar torsion, i.e., T=T μ νλ S μ νλ =0 and its space-time is axially symmetric. It is shown that this solution can be rewritten as a product of three matrices, two local Lorentz transformations and one diagonal tetrad field. The local Lorentz transformations represent “so(3)” and a boost transformation and the diagonal tetrad reproduce the same metric field of the original tetrad. 相似文献
18.
L. J. Gleeson 《Astrophysics and Space Science》1971,10(3):471-485
A complete solution has been obtained of the steady-state transport equations, including energy losses, for cosmic-rays in the interplanetary region for conditions in which diffusive transport is negligible and convective effects dominate. The region of validity of the solution will in general be a shell between heliocentric radiiR 1 andR 2 (R 2 may be infinite). The precise range of kinetic energyT and heliocentric radiusr in which the solution is valid is not known but it appears to be applicable in the vicinity of Earth to protons withT≤1 MeV. ForT～0.5 MeV near Earth,R 1 may be ～0.5 AU andR 1 will decrease asT, observed near Earth, decreases. The solution is simple in form but quite general; it predicts the differential number densityU (r, T) in terms of that observed at radius a (near Earth, say). Thus it may be quite useful in interpreting and co-ordinating steady-state cosmicray observations atT～1 MeV. The differential and integral intensities, differential anisotropy and differential radial-gradient at (r, T) also are determined. A simple interpretation of the solution is given in terms of energy losses due to adiabatic deceleration of the particles as they are being convected outward from the Sun. This leads to the useful notion of following a particle in (r, T) as it increasesr and decreasesT. Particles convected from the outer corona to Earth decrease their kinetic energy by factor ～500.Following a particle the Compton-Getting factor remains constant. Particles observed at (a, T) in convective transport have come from nearer the Sun; they may be of solar origin but may also be of galactic origin having penetrated tor<R 1相似文献
19.
C. Lozanovski 《Astrophysics and Space Science》2014,351(1):371-376
A class of purely magnetic diagonal Bianchi type VI h Cosmologies is investigated. If the energy-momentum tensor is specialized to that of a perfect fluid with (non-zero) heat-flux, with respect to the co-moving fluid 4-velocity, then the only solution is of Bianchi type V and un-physical. Further, it is shown that if certain metric functions are functionally related then the spacetime is conformally flat. Unfortunately, all these results (somewhat indirectly) invalidate a claim by Kumar and Srivastava of finding a non-conformally flat purely magnetic diagonal Bianchi type V cosmology. Finally, we consider non-zero anisotropic pressure in place of non-zero heat flux. It is shown that these spacetimes are necessarily Bianchi type VI 0. We highlight the fact that there is a known solution that generalizes the purely magnetic perfect fluid Wylleman-Van den Bergh spacetime. Physical properties of this solution are discussed. 相似文献
20.
A new solution of the magnetospheric heat equations capable of covering the whole region from 300 km along a field line to the equatorial plane has been achieved by adapting the searching procedure of Murphy (1974). It has been found that the protonospheric heat reservoir is sufficient to maintain Te >Tn down to the height of the F2-peak electron density all through the night at mid-latitudes. Full solution of the equations has also shown that Ti >Te in the protonosphere at night and the ions constitute a significant source of heat for the electrons. 相似文献