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1.
We revisit a set of symplectic variables introduced by Andre Deprit (Celest Mech 30, 181–195, 1983), which allows for a complete symplectic reduction in rotation invariant Hamiltonian systems, generalizing to arbitrary dimension
Jacobi’s reduction of the nodes. In particular, we introduce an action-angle version of Deprit’s variables, connected to the
Delaunay variables, and give a new hierarchical proof of the symplectic character of Deprit’s variables. 相似文献
2.
Hasmukh K. Tank 《Astrophysics and Space Science》2011,336(2):341-343
This letter points out that the values of ‘critical-acceleration’ of MOND, and the ‘accelerated-expansion’ of the universe
are just two of the fourteen strikingly equal values of accelerations recurring in different physical situations. Some of
them could be explained by a new law of equality of potential-energy and energy-of-mass of reasonably-independent systems
(Tank in Astrophys. Space Sci. 330:203–205, 2010; Tank in Adv. Stud. Theor. Phys. 5:45–55, 2011). This new conservation-law, of equality of potential-energy, energy-of-mass and ‘kinetic-energy’ may be a clue to understand
MOND, and the ‘accelerated-expansion’ of the universe. Alternative expressions for the cosmological red-shift, the ‘critical-acceleration’
of MOND and Newton’s law of universal gravitation are also presented for comparison of three different accelerations. 相似文献
3.
Anirudh Pradhan Hassan Amirhashchi Rekha Jaiswal 《Astrophysics and Space Science》2011,334(2):249-260
A new class of dark energy models in a Locally Rotationally Symmetric Bianchi type-II (LRS B-II) space-time with variable
equation of state (EoS) parameter and constant deceleration parameter have been investigated in the present paper. The Einstein’s
field equations have been solved by applying a variation law for generalized Hubble’s parameter given by Berman: Nuovo Cimento
74:182 (1983) which generates two types of solutions for the average scale factor, one is of power-law type and other is of the exponential-law
form. Using these two forms, Einstein’s field equations are solved separately that correspond to expanding singular and non-singular
models of the universe respectively. The dark energy EoS parameter ω is found to be time dependent and its existing range for both models is in good agreement with the three recent observations
of (i) SNe Ia data (Knop et al.: Astrophys. J. 598:102 (2003)), (ii) SNe Ia data collaborated with CMBR anisotropy and galaxy clustering statistics (Tegmark et al.: Astrophys. J. 606:702 (2004)) and latest (iii) a combination of cosmological datasets coming from CMB anisotropies, luminosity distances of high redshift
type Ia supernovae and galaxy clustering (Hinshaw et al.: Astrophys. J. Suppl. 180:225 (2009); Komatsu et al. Astrophys. J. Suppl. 180:330 (2009)). The cosmological constant Λ is found to be a positive decreasing function of time and it approaches a small positive value
at late time (i.e. the present epoch) which is corroborated by results from recent supernovae Ia observations. The physical
and geometric behaviour of the universe have also been discussed in detail. 相似文献
4.
An axially symmetric non-static space-time is considered in the presence of thick domain walls in the scalar–tensor theories
formulated by Brans and Dicke (Phys. Rev. 124:925, 1961) and Saez and Ballester (Phys. Lett. A 113:467, 1985). Exact cosmological models, in both the theories, are presented with the help of special law of variation proposed by Berman
(Nuovo Cim. B 74:182, 1983), for Hubble’s parameter. Some physical and kinematical properties of the models are discussed.
相似文献
5.
In the framework of ‘microscopic’ theory of black holes (J. Phys. Soc. Jpn. Suppl. B 70, 84, 2001; Astrophys. USSR 4, 659, 1996; 35, 335, 1991, 33, 143, 1990, 31, 345, 1989a; Astrophys. Space Sci. 1, 1992; Dokl. Akad. Nauk USSR 309, 97, 1989b), and references therein, we address the ‘pre-radiation time’ (PRT) of neutrinos from black holes, which implies the lapse
of time from black hole’s birth till radiation of an extremely high energy neutrinos. For post-PRT lifetime, the black hole
no longer holds as a region of spacetime that cannot communicate with the external universe. We study main features of spherical
accretion onto central BH and infer a mass accretion rate onto it, and, further, calculate the resulting PRT versus bolometric
luminosity due to accretion onto black hole. We estimate the PRTs of AGN black holes, with the well-determined masses and
bolometric luminosities, collected from the literature by Woo Jong-Hak and Urry (Astrophys. J. 579, 530, 2002) on which this paper is partially based. The simulations for the black holes of masses M
BH
≃(1.1⋅106
÷4.2⋅109) M
⊙ give the values of PRTs varying in the range of about T
BH
≃(4.3⋅105
÷5.6⋅1011) yr. The derived PRTs for the 60 AGN black holes are longer than the age of the universe (∼13.7 Gyr) favored today. At present,
some of remaining 174 BHs may radiate neutrinos. However, these results would be underestimated if the reservoir of gas for
accretion in the galaxy center is quite modest, and no obvious way to feed the BHs with substantial accretion. 相似文献
6.
Maxwell’s ring-type configuration (i.e. an N-body model where the ν = Ν − 1 bodies have equal masses and are located at the vertices of a regular ν-gon while the N-th body with a different mass is located at the center of mass of the system) has attracted special attention during the
last 15 years and many aspects of it have been studied by considering Newtonian and post-Newtonian potentials (Mioc and Stavinschi
1998, 1999), homographic solutions (Arribas et al.
2007) and relative equilibrium solutions (Elmabsout 1996), etc. An equally interesting problem, known as the ring problem of (N + 1) bodies, deals with the dynamics of a small body in the combined force field produced by such a configuration. This is
the problem we are dealing with in the present paper and our aim is to investigate the variations in the dynamics of the small
body in the case that the central primary is also a radiating source and therefore acts on the particle with both gravitation
and radiation. Based on the general outlines of Radzievskii’s model, we study the permitted and the existing trapping regions
of the particle, its equilibrium locations and their parametric variations as well as the existence of focal points in the
zero-velocity diagrams. The distribution of the characteristic curves of families of planar symmetric periodic orbits and
their stability for various values of the radiation coefficient of the central body is additionally investigated. 相似文献
7.
A five dimensional Kaluza-Klein space-time is considered in the presence of prefect fluid source in the general scalar-tensor
theory of gravitation proposed by Nordtvedt (Astrophys. J. 161:1069, 1970) with the help of special law of variation for Hubble’s parameter given by Bermann (Nuovo Cimento 74B:182, 1983). A cosmological model with a negative constant deceleration parameter is obtained in this theory. Some physical properties
of the model are also discussed. 相似文献
8.
We have discussed non-linear stability in photogravitational non-planar restricted three body problem with oblate smaller
primary. By photogravitational we mean that both primaries are radiating. We normalized the Hamiltonian using Lie transform
as in Coppola and Rand (Celest. Mech. 45:103, 1989). We transformed the system into Birkhoff’s normal form. Lie transforms reduce the system to an equivalent simpler system
which is immediately solvable. Applying Arnold’s theorem, we have found non-linear stability criteria. We conclude that L
6 is stable. We plotted graphs for (ω
1,D
2). They are rectangular hyperbola. 相似文献
9.
Marcelo Samuel Berman 《Astrophysics and Space Science》2009,323(1):103-106
We present a lambda-Universe, in scalar-tensor gravity, reviewing Berman and Trevisan’s inflationary case (Berman and Trevisan
in Int. J. Theor. Phys., 2009) and then we find a solution for an accelerating power-law scale-factor.
The negativity of cosmic pressure implies acceleration of the expansion, even with Λ<0. The cosmological term, and the coupling
“constant”, are in fact, time-varying.
相似文献
10.
LRS Bianchi type-I dark energy model with variable equation of state (EoS) parameter is presented in the scalar-tensor theory
of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, 1986). To get a determinate solution of the field equations we take the help of special law of variation for Hubble’s parameter
presented by Bermann (Nuovo Cimento B 74:182, 1983) which yields a cosmological model with negative constant deceleration parameter. Some physical and kinematical properties
of the model are also discussed. 相似文献
11.
Rebecca A. Harbison Peter C. Thomas Philip C. Nicholson 《Celestial Mechanics and Dynamical Astronomy》2011,110(1):1-16
Saturn’s moon, Hyperion, is subject to strongly-varying solid body torques from its primary and lacks a stable spin state
resonant with its orbital frequency. In fact, its rotation is chaotic, with a Lyapunov timescale on the order of 100 days.
In 2005, Cassini made three close passes of Hyperion at intervals of 40 and 67 days, when the moon was imaged extensively
and the spin state could be measured. Curiously, the spin axis was observed at the same location within the body, within errors,
during all three fly-bys—~ 30° from the long axis of the moon and rotating between 4.2 and 4.5 times faster than the synchronous
rate. Our dynamical modeling predicts that the rotation axis should be precessing within the body, with a period of ~ 16 days.
If the spin axis retains its orientation during all three fly-bys, then this puts a strong constraint on the in-body precessional
period, and thus the moments of inertia. However, the location of the principal axes in our model are derived from the shape
model of Hyperion, assuming a uniform composition. This may not be a valid assumption, as Hyperion has significant void space,
as shown by its density of 544± 50 kg m−3 (Thomas et al. in Nature 448:50, 2007). This paper will examine both a rotation model with principal axes fixed by the shape model, and one with offsets from the
shape model. We favor the latter interpretation, which produces a best-fit with principal axes offset of ~ 30° from the shape
model, placing the A axis at the spin axis in 2005, but returns a lower reduced χ
2 than the best-fit fixed-axes model. 相似文献
12.
The regularization of a new problem, namely the three-body problem, using ‘similar’ coordinate system is proposed. For this
purpose we use the relation of ‘similarity’, which has been introduced as an equivalence relation in a previous paper (see
Roman in Astrophys. Space Sci. doi:, 2011). First we write the Hamiltonian function, the equations of motion in canonical form, and then using a generating function,
we obtain the transformed equations of motion. After the coordinates transformations, we introduce the fictitious time, to
regularize the equations of motion. Explicit formulas are given for the regularization in the coordinate systems centered
in the more massive and the less massive star of the binary system. The ‘similar’ polar angle’s definition is introduced,
in order to analyze the regularization’s geometrical transformation. The effect of Levi-Civita’s transformation is described
in a geometrical manner. Using the resulted regularized equations, we analyze and compare these canonical equations numerically,
for the Earth-Moon binary system. 相似文献
13.
A locally rotationally symmetric Bianchi type-II (LRS B-II) space-time with variable equation of state (EoS) parameter and
constant deceleration parameter have been investigated in the scalar-tensor theory proposed by Saez and Ballester (Phys. Lett.
A 113:467, 1986). The scalar-tensor field equations have been solved by applying variation law for generalized Hubble’s parameter given by
Bermann (Nuovo Cimento 74:182, 1983). The physical and kinematical properties of the model are also discussed. 相似文献
14.
Marcelo Samuel Berman 《Astrophysics and Space Science》2012,337(1):477-481
In a previous paper (Berman, in Astrophys. Space Sci., 2011), we showed how to prove the two Pioneers Anomalies, and now we add the fly-bys, by means of a rotating Universe. We discuss
Einstein’s Machian program, which we find as being fullfilled. Godlowski et al. (Los Alamos Archives, 2003) idea for a rotating General Relativistic Universe, led us to the adopted model. Updated evidence on rotation is cited (Godlowski,
in Los Alamos Archives, 2011; Ni in Phys. Rev. Lett. 107(5):051103, 2011). We conclude that a rotating and expanding Universe may be the unique solution to the apparent divergences between Einstein
and Mach. This is cosmologically important. 相似文献
15.
A spatially homogeneous Bianchi type-III space-time is considered in the presence of perfect fluid source in the frame work of f(R,T) gravity (Harko et al. in Phys. Rev. D 84:024020, 2011) with the help of a special law of variation for Hubble’s parameter proposed by Bermann (Nuovo Cimento B 74:182, 1983). A cosmological model with an appropriate choice of the function f(T) has been constructed. The physical behavior of the model is studied. 相似文献
16.
Halo coronal mass ejections (HCMEs) are responsible of the most severe geomagnetic storms. A prediction of their geoeffectiveness
and travel time to Earth’s vicinity is crucial to forecast space weather. Unfortunately, coronagraphic observations are subjected
to projection effects and do not provide true characteristics of CMEs. Recently, Michalek (Solar Phys.
237, 101, 2006) developed an asymmetric cone model to obtain the space speed, width, and source location of HCMEs. We applied this technique
to obtain the parameters of all front-sided HCMEs observed by the SOHO/LASCO experiment during a period from the beginning
of 2001 until the end of 2002 (solar cycle 23). These parameters were applied for space weather forecasting. Our study finds
that the space speeds are strongly correlated with the travel times of HCMEs to Earth’s vicinity and with the magnitudes related
to geomagnetic disturbances. 相似文献
17.
K. S. Adhav S. D. Katore R. S. Rane K. S. Wankhade 《Astrophysics and Space Science》2009,323(1):87-90
In this paper, we have investigated spatially homogeneous isotropic Friedmann cosmological model with bulk viscosity and zero-mass
scalar field in Lyra manifold. The cosmological models are obtained with the help of the special law of variation for Hubble’s
parameter proposed by Bermann (Nuovo Cimento 74B:182, 1983) and power law relation. Some physical properties of the models are discussed. 相似文献
18.
The present study deals with a spatially homogeneous and anisotropic Bianchi-I cosmological models representing massive strings.
The energy-momentum tensor, as formulated by Letelier (1983), has been used to construct massive string cosmological models for which we assume the expansion scalar in the models is
proportional to one of the components of shear tensor. The Einstein’s field equations have been solved by applying a variation
law for generalized Hubble’s parameter in Bianchi-I space-time. We have analysed a comparative study of accelerating and decelerating
models in the presence of string scenario. The study reveals that massive strings dominate in the decelerating universe whereas
strings dominate in the accelerating universe. The strings eventually disappear from the universe for sufficiently large times,
which is in agreement with current astronomical observations. 相似文献
19.
We have obtained Bianchi type-III cosmological model with strange quark matter attached to the string cloud in general relativity.
For solving the Einstein’s field equations the relation [C=A
n
] between metric coefficients C and A is used. Also, some physical and kinematic properties of the model are discussed.The results are analogous to results obtained
by Yilmaz (Gen. Rel. Grav. 38:1397–1406, 2006). 相似文献
20.
Rodica Roman 《Astrophysics and Space Science》2011,335(2):475-483
A new equivalence relation, named relation of ‘similarity’ is defined and applied in the restricted three-body problem. Using
this relation, a new class of trajectories (named ‘similar’ trajectories) are obtained; they have the theoretical role to
give us new details in the restricted three-body problem. The ‘similar’ coordinate systems allow us in addition to obtain
a unitary and an elegant demonstration of some analytical relations in the Roche geometry. As an example, some analytical
relations published by Seidov (in Astrophys. J. 603:283, 2004) are demonstrated. 相似文献