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1.
The Sitnikov's Problem is a Restricted Three-Body Problem of Celestial Mechanics depending on a parameter, the eccentricity,e. The Hamiltonian,H(z, v, t, e), does not depend ont ife=0 and we have an integrable system; ife is small the KAM Theory proves the existence of invariant rotational curves, IRC. For larger eccentricities, we show that there exist two complementary sequences of intervals of values ofe that accumulate to the maximum admissible value of the eccentricity, 1, and such that, for one of the sequences IRC around a fixed point persist. Moreover, they shrink to the planez=0 ase tends to 1.  相似文献   

2.
Inferences are made about the relationship that existed between the Ushnus, pyramid-shaped, terraced structures used by the Incas in the most important ceremonies of the Tawantinsuyo, and Inka Astronomy. We draw attention to Ayni, Kawsaypacha, Duality, and Tinkuy principles, multidimensional codes of conduct and wisdom that are at the root of the Andean cosmovision and on their perception of the world and the Cosmos. These principles, examined as postulates, allow to elaborate axiomatic propositions to identify the Ushnus with ancient Astronomy practices. In a complementary statement, starting from a bi-conditional proposition, we may infer through reciprocal corollaries that the Inka earliest roots to a holistic learning and educational ambient in the Tawantinsuyo was not elitist, instead it was based on a epistemological construct that differs from the corresponding Western educational ambients. An epistemological and cognitive approach allows to identify an ancient elaborate process of knowledge construction, based on the four fundamental principles, corresponding to different levels of assimilation and comprehension. As a complementary aspect, we identify some of the most preserved Ushnus of the Inka “Empire.” Then we complement this contribution with a broader interpretation for the Ushnus.  相似文献   

3.
Based on an analysis of the catalog of magnetic fields, we have investigated the statistical properties of the mean magnetic fields for OB stars. We show that the mean effective magnetic field B of a star can be used as a statistically significant characteristic of its magnetic field. No correlation has been found between the mean magnetic field strength B and projected rotational velocity of OB stars, which is consistent with the hypothesis about a fossil origin of the magnetic field. We have constructed the magnetic field distribution function for B stars, F(B), that has a power-law dependence on B with an exponent of ≈−1.82. We have found a sharp decrease in the function F(B) for B ⩽ 400 G that may be related to rapid dissipation of weak stellar surface magnetic fields.  相似文献   

4.
The debate concerning the viability of f(R)-gravity as a natural extension of General Relativity could be realistically addressed by using results coming from binary pulsars like PSR 1913 + 16. To this end, we develop a quadrupolar approach to the gravitational radiation for a class of analytic f(R)-models. We show that experimental results are compatible with a consistent range of f(R)-models. This means that f(R)-gravity is not ruled out by the observations and gravitational radiation (in strong field regime) could be a test-bed for such theories.  相似文献   

5.
The D'Alembert model for the spin/orbit problem in celestial mechanics is considered. Using a Hamiltonian formalism, it is shown that in a small neighborhood of a p:q spin/orbit resonance with (p,q) different from (1,1) and (2,1) the 'effective' D'Alembert Hamiltonian is a completely integrable system with phase space foliated by maximal invariant curves; instead, in a small neighborhood of a p:q spin/orbit resonance with (p,q) equal to (1,1) or (2,1) the 'effective' D'Alembert Hamiltonian has a phase portrait similar to that of the standard pendulum (elliptic and hyperbolic equilibria, separatrices, invariant curves of different homotopy). A fast averaging with respect to the 'mean anomaly' is also performed (by means of Nekhoroshev techniques) showing that, up to exponentially small terms, the resonant D'Alembert Hamiltonian is described by a two-degrees-of-freedom, properly degenerate Hamiltonian having the lowest order terms corresponding to the 'effective' Hamiltonian mentioned above.  相似文献   

6.
An effective Microcanonical Thermodynamics of self gravitating systems(SGS) is proposed, analyzing the well known obstacles thought to prevent the formulation of a rigorous Statistical Mechanics (SM), as those due to the formal unboundedness of available phase space and to the unscreened, long range, nature of the interaction. The latter feature entails the well known inequivalence of statistical ensembles, puts clearly into question the meaning, for these systems, of the Thermodynamic Limit, and rules out the use of canonical and grand-canonical ensembles. As to the first obstacle, we argue nevertheless that a hierarchy of timescales exist such that, at any finite time, the volume of the effectively available region of phase space is indeed finite, and that the dynamics satisfies a strong chaos criterion, leading to a fast, increasingly uniform, spreading of orbits over an effectively invariant subset of the constant (N,V,E) surface; thus leading to the definition of a secularly evolving, generalized microcanonical ensemble, which allows to define an (almost extensive) effective entropy and to derive self-consistent definitions for other thermodynamic variables, giving thus an orthode for SGS. Moreover, a Second Law-like criterion allows to single out the hierarchy of secular equilibria describing, for any finite time, the macroscopic behaviour of SGS. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

7.
C. Barban  F. Hill 《Solar physics》2004,220(2):399-402
Using Severino's model, we estimate the amount of coherent correlated and uncorrelated background and incoherent noise components needed to reproduce the following four helioseismic spectra: V power, I power, V–I phase difference and V–I coherence, using GONG and MDI data. We confirm that a coherent correlated component of 10-15% of the total background and noise is needed in both V and I and that a larger amount of coherent uncorrelated background is needed for MDI data compared to GONG data to compensate for a smaller incoherent noise.  相似文献   

8.
Using two volume-limited Main galaxy samples of the Sloan Digital Sky Survey Data Release 6 (SDSS DR6), we have explored the difference of the environmental dependence of u-, g-, r-, i-, and z-band luminosities between galaxies above and below the value of M r*. It turns out that in the luminous volume-limited sample, all the five band luminosities strongly correlate with local environments. Because the u-band luminosity of galaxies still strongly depends on local environments in the faint volumelimited sample, we conclude that M r* is not an important characteristic parameter for the environmental dependence of the u-band luminosity. It is worth noting that for the u-band, the subsample at low density has a higher proportion of luminous galaxies and a lower proportion of faint galaxies than the one at high density, which is opposite to widely accepted conclusion: luminous galaxies exist preferentially in the densest regions of the universe, but faint galaxies are located preferentially in low density regions. Our results show that the environmental dependence of luminosity is not a single trend in different luminosity regions and for different bands.  相似文献   

9.
We present the first long‐term Johnson UBVR observations and comprehensive photometric analysis of the W UMa‐type eclipsing binary V2612 Oph. Observations in the time interval between 2003 and 2009 enabled us to reveal the seasonal and long‐term variations of the light curve. Hence, we found that the mean brightness level of the light curve shows a variation with a period of 6.7 years. Maximum and minimum brightness levels of the light curve exhibit a variation from year to year which we attribute to a solar‐like activity. The O – C variation of eclipse timings of the system shows a decreasing parabolic trend and reveals a period decrease at a rate of P = 6.27×10‐7 day yr‐1 with an additional low‐amplitude sinusoidal variation that has a similar period as the long‐term brightness variations. Our light curve analysis shows that the system is a W‐subtype W UMa eclipsing binary. We calculated masses and radii of the primary and secondary components as M1 = 1.28 M⊙, M2 = 0.37 M⊙ and R1 = 1.31 R⊙, R2 = 0.75 R⊙, respectively. The derived absolute photometric parameters allow us to calculate a distance of 140 pc, which confirms that the system is a foreground star in the sky field of the Galactic open cluster NGC 6633. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

10.
Recently Alexander and Gulyaev have suggested that the apparent decrease in impact broadening of radio recombination lines seen at high principal quantum number n may be a product of the data reduction process, possibly resulting from the presence of noise on the telescope spectra that is not present on the calculated comparison spectra. This is an interesting proposal. However, there are serious problems with their analysis that need to be pointed out. Perhaps the most important of these is the fact that for principal quantum numbers below n=200, where the widths are not in question, their processed generated profile widths do not fit the widths of the processed lines obtained at the telescope. After processing, the halfwidths of the generated and telescope profiles must agree below n=200 if we are to believe that the processed generated linewidths above n=200 are meaningful. Theirs do not. Furthermore, we find that after applying the linewidth reduction factors found by Alexander and Gulyaev for their noise added profiles to our generated profiles to simulate their noise adding effect, the processed widths we obtain still do not come close to explaining the narrowing seen in the telescope lines for n values in the range 200<n<250. It is concluded that what is needed to solve this mystery is a completely new approach using a different observing technique instead of simply a further manipulation of the frequency-switched data.  相似文献   

11.
It is shown that quantum vacuum fluctuations give rise to a curvature of space-time equivalent to a cosmological constant, that is a homogeneous energy density ρ and pressure p fulfilling −p=ρ>0. The fact that the fluctuations produce curvature, even if the vacuum expectation of the energy vanishes, is a consequence of the non-linear character of the Einstein equation. A calculation is made, involving plausible hypotheses within quantized gravity, which establishes a relation between the two-point correlation of the vacuum fluctuations and the space-time curvature. Arguments are given which suggest that the density ρ might be of order the “dark energy” density currently assumed to explain the observed accelerated expansion of the universe.  相似文献   

12.
The magnetic field in the solar corona plays an important role in coronal heating, flaring activity and many other phenomena studied on the Sun. Magnetic topology is frequently used to understand complicated coronal magnetic fields. By calculating the skeleton of a field, it is possible to build up a sophisticated representation of the key elements of a field’s configuration. This paper determines a simple relation between the numbers of separators (X), coronal null points (Nc), flux domains (D) and flux sources (S) in such a configuration: D=X+S−Nc−1. This equation is used to explain the behaviour of some of the bifurcations found in Magnetic Charge Topology, and to show that a one-to-one relationship exists between the number of circuits in the domain graph and the augmented null graph. Finally, it is shown that in quiet-Sun regions, the number of separators is approximately proportional to the number of flux sources.  相似文献   

13.
We have performed an ecliptic survey of the Kuiper belt, with an areal coverage of 8.9 square degrees to a 50% limiting magnitude of , and have detected 88 Kuiper belt objects, roughly half of which received follow-up 1–2 months after detection. Using this survey data alone, we have measured the luminosity function of the Kuiper belt, thus avoiding any biases that might come from the inclusion of other observations. We have found that the Cold population defined as having inclinations less than 5° has a luminosity function slope αCold = 0.82 ± 0.23, and is different from the Hot population, which has inclinations greater than 5° and a luminosity function slope αHot = 0.35 ± 0.21. As well, we have found that those objects closer than 38 AU have virtually the same luminosity function slope as the Hot population. This result, along with similar findings of past surveys demonstrates that the dynamically Cold Kuiper belt objects likely have a steep size distribution, and are unique from all of the excited populations which have much shallower distributions. This suggests that the dynamically excited population underwent a different accretion history and achieved a more evolved state of accretion than the Cold population. As well, we discuss the similarities of the Cold and Hot populations with the size distributions of other planetesimal populations. We find that while the Jupiter family comets and the scattered disk exhibit similar size distributions, a power-law extrapolation to small sizes for the scattered disk cannot account for the observed influx of comets. As well, we have found that the Jupiter Trojan and Hot populations cannot have originated from the same parent population, a result that is difficult to reconcile with scattering models similar to the NICE model. We conclude that the similarity between the size distributions of the Cold population and the Jupiter Trojan population is a striking coincidence.  相似文献   

14.
In this paper I deal with the WD0137-349 binary system consisting of a white dwarf (WD) and a brown dwarf (BD) in a close circular orbit of about 116 min. I, first, constrain the admissible range of values for the inclination i by noting that, from looking for deviations from the third Kepler law, the quadrupole mass moment Q would assume unlikely large values, incompatible with zero at more than 1-sigma level for i≲35 deg and i≳43 deg. Then, by conservatively assuming that the most likely values for i are those that prevent such an anomalous behavior of Q, i.e. those for which the third Kepler law is an adequate modeling of the orbital period, I obtain i=39±2 deg. Such a result is incompatible with the value i=35 deg quoted in literature by more than 2 sigma. Conversely, it is shown that the white dwarf’s mass range obtained from spectroscopic measurements is compatible with my experimental range, but not for i=35 deg. As a consequence, my estimate of i yields an orbital separation of a=(0.59±0.05)R⊙ and an equilibrium temperature of BD of T eq=(2087±154) K which differ by 10% and 4%, respectively, from the corresponding values for i=35 deg.  相似文献   

15.
It has recently been shown that Jupiter Trojans may exhibit chaotic behavior, a fact that has put in question their presumed long term stability. Previous numerical results suggest a slow dispersion of the Trojan swarms, but the extent of the ‘effective’ stability region in orbital elements space is still an open problem. In this paper, we tackle this problem by means of extensive numerical integrations. First, a set of 3,200 fictitious objects and 667 numbered Trojans is integrated for 4 Myrs and their Lyapunov time, TL, is estimated. The ones following chaotic orbits are then integrated for 1 Gyr, or until they escape from the Trojan region. The results of these experiments are presented in the form of maps of TLand the escape time, TE, in the space of proper elements. An effective stability region for 1 Gyr is defined on these maps, in which chaotic orbits also exist. The distribution of the numbered Trojans follows closely the TE=1 Gyr level curve, with 86% of the bodies lying inside and 14% outside the stability region. This result is confirmed by a 4.5 Gyr integration of the 246 chaotic numbered Trojans, which showed that 17% of the numbered Trojans are unstable over the age of the solar system. We show that the size distributions of the stable and unstable populations are nearly identical. Thus, the existence of unstable bodies should not be the result of a size-dependent transport mechanism but, rather, the result of chaotic diffusion. Finally, in the large chaotic region that surrounds the stability zone, a statistical correlation between TLandTE is found.  相似文献   

16.
Measurements of the north-south (B z component of the interplanetary field as compiled by King (1975) when organized into yearly histograms of the values of ¦B z ¦ reveal the following. (1) The histograms decrease exponentially from a maximum occurrence frequency at the value ¦B z ¦ = 0. (2) The slope of the exponential on a semi-log plot varies systematically roughly in phase with the sunspot number in such a way that the probability of large values of ¦B z ¦ is much greater in the years near sunspot maximum than in the years near sunspot minimum. (3) There is a sparsely populated high-value tail, for which the data are too meager to discern any solar cycle variation. The high-value tail is perhaps associated with travelling interplanetary disturbances. (4) The solar cycle variations of B z and the ordinary indicators of solar activity are roughly correlated. (5) The solar cycle variation of B z is distinctly different than that of the solar wind speed and that of the geomagnetic Ap disturbance index.Now at the Aerospace Corporation, El Segundo, Calif. 90245, U.S.A.  相似文献   

17.
Problems where impact broadened radio recombination lines appeared narrower than predicted first showed up ∼40 years ago at frequencies below ∼3 GHz. But it was soon found that the observations could be explained by throwing out the uniform density models and replacing them with variable density ones. However, this problem re-appeared recently when a mysterious line narrowing above quantum numbers of (n,Δn)=(202,8) was reported from sensitive observations of Orion and W51 near 6 GHz. Here it is demonstrated that the narrowing is unlikely to be caused by the data processing technique and therefore must be source related. It is further demonstrated that the observed line narrowing can be tied to one of the fundamental properties of radio recombination lines; namely the fact that the spacing of adjacent n-transitions increases with frequency. The line narrowing is observed to begin when the n-transition density, D n , exceeds ∼11.6 transitions per GHz. This may imply that it is somehow related either to a previously overlooked effect in the impact broadening process, or to some unknown parallel process, that is tied to the separation between adjacent n-transitions. Based on these results it can be concluded, as has also been concluded in several theoretical investigations, that the observed line narrowing is not tied to a fixed range of either n or Δn.  相似文献   

18.
We consider the inversion of a problem put by A. EINSTEIN and E. G. STRAUS , that is, we ask for restrictions on the scaling factor R(t) of the ROBERTSON WALKER metric and the functions H2(r') and A2(r') of a spherically symmetric and static vacuum metric, which are consequences of the requirement that the vacuum metric shall pass continuously differentiable into the ROBERTSON WALKER metric at a certain value rb of the comoving radial coordinate r.  相似文献   

19.
We study the dynamical evolution of an f(R) model of gravity in a viscous and anisotropic background which is given by a Bianchi type-I model of the Universe. We find viable forms of f(R) gravity in which one is exactly the Einsteinian model of gravity with a cosmological constant and other two are power law f(R) models. We show that these two power law models are stable with a suitable choice of parameters. We also examine three potentials which exhibit the potential effect of f(R) models in the context of scalar tensor theory. By solving different aspects of the model and finding the physical quantities in the Jordan frame, we show that the equation of state parameter satisfy the dominant energy condition. At last we show that the two power law f(R) models behave like quintessence model at late times and also the shear coefficient viscosity tends to zero at late times.  相似文献   

20.
Barnes  G.  Cally  P.S. 《Solar physics》2000,193(1-2):373-382
Sunspots are strong absorbers of f and p modes. A possible absorption mechanism is direct conversion to slow magnetoacoustic waves. Calculations based on vertical magnetic field models show that this works well for f modes, but is inadequate for p modes. Using a very simple shallow spot model, in which the effects of the magnetic field are accounted for solely by a surface condition, we investigate the possibility that p modes first scatter into f modes inside the spot, which are then more susceptible to conversion to slow modes. We find that the coupling between an incident p mode and the internal f mode is unlikely to be strong enough to account for the observed absorption, but that the incident modes do couple strongly to the acoustic jacket in some cases, leading to a region immediately around the sunspot where a significant fraction of the surface velocity is due to the jacket modes.  相似文献   

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