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1.
M. E. McCulloch 《Astrophysics and Space Science》2014,349(2):957-959
It is shown here that Newton’s gravity law can be derived from the uncertainty principle. The idea is that as the distance between two bodies in mutual orbit decreases, their uncertainty of position decreases, so their momentum and hence the force on them must increase to satisfy the uncertainty principle. When this result is summed over all the possible interactions between the Planck masses in the two bodies, Newton’s gravity law is obtained. This model predicts that masses less than the Planck mass will be unaffected by gravity and so it may be tested by looking for an abrupt decrease in the density of space dust, for masses above the Planck mass. 相似文献
2.
In this paper it is suggested that inclusion of mutual gravitational interactions among the particles in the early dense universe
can lead to a ‘pre-big bang’ scenario, with particle masses greater than the Planck mass implying an accelerating phase of
the universe, which then goes into the radiation phase when the masses fall below the Planck mass. The existence of towers
of states of such massive particles (i.e. multiples of Planck mass) as implied in various unified theories, provides rapid
acceleration in the early universe, similar to the usual inflation scenario, but here the expansion rate goes over ‘smoothly’
to the radiation dominated universe when temperature becomes lower than the Planck temperature. 相似文献
3.
We propose a decay signature for non-thermal small black holes with masses in the TeV range which can be discovered by neutrino observatories. The black holes would result due to the impact between ultra high energy neutrinos with nuclei in water or ice and decay instantaneously. They could be produced if the Planck scale is in the few TeV region and the highly energetic fluxes are large enough. Having masses close to the Planck scale, the typical decay mode for these black holes is into two particles emitted back-to-back. For a certain range of angles between the emitted particles and the center of mass direction of motion, it is possible for the detectors to measure separate muons having specific energies and their trajectories oriented at a large enough angle to prove that they are the result of a back-to-back decay event. 相似文献
4.
The most recently celebrated cosmological implications of the cosmic microwave background studies with WMAP (2006), though fascinating by themselves, do, however, create some extremely hard conceptual challenges for the present‐day cosmology. These recent extremely refined WMAP observations seem to reflect a universe which was extremely homogeneous at the recombination age and thus is obviously causally closed at the time of the cosmic recombination era. From the very tiny fluctuations apparent at this early epoch the presently observable nonlinear cosmic density structures can, however, only have grown up, if in addition to a mysteriously high percentage of dark matter an even higher percentage of dark energy is admitted as drivers of the cosmic evolution. The required dark energy density, on the other hand, is nevertheless 120 orders of magnitude smaller then the theoretically calculated value. These are outstanding problems of present day cosmology onto which we are looking here under new auspices. We shall investigate in the following, up to what degree a universe simply abolishes all these outstanding problems in case it reveals itself as an universe of constant total energy. As we shall show basic questions like: How could the gigantic mass of the universe of about 1080 proton masses at all become created? – Why is the presently recognized and obviously indispensable cosmic vacuum energy density so terribly much smaller than is expected from quantum theoretical considerations, but nevertheless terribly important for the cosmic evolution? – Why is the universe within its world horizon a causally closed system? –, can perhaps simply be answered, when the assumption is made that the universe has a constant total energy with the consequence that the total mass density of the universe (matter and vacuum) scales with . Such a scaling of matter and vacuum energy abolishes the horizon problem, and the cosmic vacuum energy density can easily be reconciled with its theoretical expectation values. In this model the mass of the universe increases linearly with the world extension Ru and can grow up from a Planck mass as a vacuum fluctuation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
Seeking a possible explanation for recent data indicating a space-time variation of the electron-to-proton mass ratio within the Milky Way, we consider a phenomenological model where the effective fermion masses depend on the local value of the Weyl tensor. We contrast the required values of the model’s free parameters with bounds obtained from modern tests on the violation of the weak equivalence principle and we find that these quantities are incompatible. This result indicates that the variation of nucleon and electron masses through a coupling with the Weyl tensor is not a viable model. 相似文献
6.
We provide a generalized discussion of tidal evolution to arbitrary order in the expansion of the gravitational potential
between two spherical bodies of any mass ratio. To accurately reproduce the tidal evolution of a system at separations less
than 5 times the radius of the larger primary component, the tidal potential due to the presence of a smaller secondary component
is expanded in terms of Legendre polynomials to arbitrary order rather than truncated at leading order as is typically done
in studies of well-separated system like the Earth and Moon. The equations of tidal evolution including tidal torques, the
changes in spin rates of the components, and the change in semimajor axis (orbital separation) are then derived for binary
asteroid systems with circular and equatorial mutual orbits. Accounting for higher-order terms in the tidal potential serves
to speed up the tidal evolution of the system leading to underestimates in the time rates of change of the spin rates, semimajor
axis, and mean motion in the mutual orbit if such corrections are ignored. Special attention is given to the effect of close
orbits on the calculation of material properties of the components, in terms of the rigidity and tidal dissipation function,
based on the tidal evolution of the system. It is found that accurate determinations of the physical parameters of the system,
e.g., densities, sizes, and current separation, are typically more important than accounting for higher-order terms in the
potential when calculating material properties. In the scope of the long-term tidal evolution of the semimajor axis and the
component spin rates, correcting for close orbits is a small effect, but for an instantaneous rate of change in spin rate,
semimajor axis, or mean motion, the close-orbit correction can be on the order of tens of percent. This work has possible
implications for the determination of the Roche limit and for spin-state alteration during close flybys. 相似文献
7.
Ignacio MosqueiraPaul R. Estrada 《Icarus》2002,158(2):545-556
An explanation of the dynamical mechanism for apse alignment of the eccentric uranian rings is necessary before observations can be used to determine properties such as ring masses, particle sizes, and elasticities. The leading model (P. Goldreich and S. Tremaine 1979, Astron J.84, 1638-1641) relies on the ring self-gravity to accomplish this task, yet it yields equilibrium masses which are not in accord with Voyager radio measurements. We explore possible solutions such that the self-gravity and the collisional terms are both involved in the process of apse alignment. We consider limits that correspond to a hot and a cold ring, and we show that pressure terms may play a significant role in the equilibrium conditions for the narrow uranian rings. In the cold ring case, where the scale height of the ring near periapse is comparable to the ring particle size, we introduce a new pressure correction pertaining to a region of the ring where the particles are locked in their relative positions and jammed against their neighbors and the velocity dispersion is so low that the collisions are nearly elastic. In this case, we find a solution such that the ring self-gravity maintains apse alignment against both differential precession (m=1 mode) and the fluid pressure. We apply this model to the uranian α ring and show that, compared to the previous self-gravity model, the mass estimate for this ring increases by an order of magnitude. In the case of a hot ring, where the scale height can reach a value as much as 50 times the particle size, we find velocity dispersion profiles that result in pressure forces which act in such a way as to alter the ring equilibrium conditions, again leading to a ring mass increase of an order of magnitude. We find that such a velocity dispersion profile would require a different mechanism than is currently envisioned for establishing a heating/cooling balance in a finite-sized, inelastic particle ring. Finally, we introduce an important correction to the model of E. I. Chiang and P. Goldreich (2000, Astrophys. J.540, 1084-1090.). These authors relied on collisional forces in the last ∼100 m of an ∼10 km wide ring to increase ring equilibrium masses by up to a factor of ∼100. However, their treatment of ring edges as one-sided surface density drops leads to a strong dependence of the ring mass on the adjustable parameter λ (the length scale over which the ring's optical depth drops from order unity to zero at the edge). A treatment of the ring edges that takes into account their ridgelike structure retains the increase of ring mass of the order of ∼100 for a 10 km wide ring, while exhibiting weak dependence on λ. We conclude that a modified Chiang-Goldreich model can likely account for the masses of narrow, eccentric planetary rings; however, the role of shepherd satellites both in forming ring edges and in altering the streamline precession conditions near them needs to be explored further. It is also unclear whether a fully self-consistent ring model allows for the possibility of rings with negative eccentricity gradients. 相似文献
8.
We derive strong constraints on the Yukawa couplings and the vacuum expectation value in the singlet majoron model. The presence of a small gravitationally induced mass for the majoron can be used to set a constraint on its vacuum expectation value. If the singlet symmetry breaking scale is larger than the electroweak symmetry breaking scale, lepton number violating interactions in equilibrium with electroweak sphaleron interactions would destroy any prior baryon asymmetry. If the baryon asymmetry is not generated at the electroweak scale or later, strong bounds on the Yukawa couplings h 10−7 and VEVs vs < vEW are derived. We also carefully rederive baryogenesis bounds on neutrino masses, finding that in general they apply not to the masses themselves, but only to related parameters, and they are numerically somewhat less stringent than has previously been claimed. 相似文献
9.
Charged boson stars and vacuum instabilities 总被引：1，自引：0，他引：1
We consider charged boson stars and study their effect on the structure of the vacuum. For very compact particle like “stars”, with constituent mass m* close to the Planck mass mPl, i.e. m2* = O(m2Pl), we argue that there is electric charge Zc, which, primarily, is due to the formation of a pion condensate (Zc 0.5−1e, where is the fine structure constant and e is the electric charge of the positron). If the charge of the “star” is larger than Zc we find numerical evidence for a complete screening indicating a limiting charge for a very compact object. There is also a less efficient competing charge screening mechanism due to spontaneous electron-positron pair creation in which case Zc −1e. Astrophysical and cosmological abundances of charged compact boson stars are briefly discussed in terms of dark matter. 相似文献
10.
In understanding the nucleosynthesis of the elements in stars, one of the most important quantities is the reaction rate and
it must be evaluated in terms of the stellar temperature T, and its determination involves the knowledge of the excitation function σ(E) of the specific nuclear reaction leading to the final nucleus. In this paper, the effect of thermonuclear reaction rates
to the pre-main sequence evolution of low mass stars having masses 0.7, 0.8, 0.9 and 1M⊙ are studied by using our modified Stellar Evolutionary Program. 相似文献
11.
New Claret evolutionary model-tracks, constructed for the first time for studying close binary systems (CBS) including tidal
evolution constants, are used to determine the age of 112 eclipsing-variable stars in the Svechnikov-Perevozkina catalog by
the method of isochrones. There is some interest in comparing the calculated ages with previous estimates obtained for these
same close binary systems using evolutionary modeltracks for individual stars taking their mass loss into account. A correlation
of the ages of the principal and secondary components is noted, which is most marked for massive close binaries with principal
components having masses M1 ≥ 3 M⊙. A rejuvenating effect is found to occur for the systems studied here as calculated on the new tracks; it is most distinct
for low-mass close binaries with a total mass M1 + M2 ≤ 3.5 M⊙ and is predicted theoretically in terms of magnetic braking. The calculated broadband grid of isochrones, from zero-age main-sequence
(ZAMS) to the age of the galaxy, can be used for estimating the ages of close binaries from other catalogs. Ages are given
for the 112 eclipsing-variable close binaries with detached components lying within the main sequence.
__________
Translated from Astrofizika, Vol. 50, No. 2, pp. 299–312 (May 2007). 相似文献
12.
We have investigated magnetostatic equilibria for coronal loops embedded in a potential magnetic field on a rotating star. We find that for any given star, there is a maximum value of the plasma pressure inside a single loop, above which no equilibrium exists. This maximum internal pressure depends on the ratio of the temperatures inside and outside the loop, and on the ratio of the plasma pressure to the magnetic pressure at the base of the external field. Thus, any loop of a large-scale field which is heated or cooled to a different temperature from its immediate surroundings, or which experiences a change in its internal pressure may eventually lose equilbrium. For some values of the base pressure and temperature ratio the relation between summit height and footpoint separation is double-valued. As the summit height of a loop is increased, its footpoint separation increases to a critical value, then decreases to zero at the maximum possible summit height. At the critical footpoint separation the slope of the loop height-footpoint separation relation becomes infinite, and no equilibrium solution exists for greater footpoint separations.We find also that the strength and scale of the field external to the flux tube is the most important factor in determining its maximum height. The effects of varying the stellar rotation rate - and, hence, the variation in pressure with height - are comparatively unimportant, even for very high rotation rates at which the point of balance between gravitational and centrifugal forces lies close to the stellar surface. In this case it is possible to find equilibrium loop solutions whose summits lie outside the centrifugal balance point.We have also investigated the effects of varying the stellar surface gravity. For stellar of fixed mass and rotation rate, the loop dimensions scale approximately linearly with the stellar radius. 相似文献
13.
The maximum acceleration at the Planck epoch is shown to be related to the maximum magnetic field and curvature as well as temperature in that era. Spin-torsion effects at that epoch also lead to same value. 相似文献
14.
Z. Horák 《Astrophysics and Space Science》1984,100(1-2):1-11
It is shown that Archimedes' principle can be generalized for external gravitational fields due to stationary macroscopic bodies. For instance, a particle immersed in a homogeneous fluid at the centre of spherical symmetry of the fluid, or anywhere in an unbounded homogenous fluid, experiences — in an external field — a force that it would experience in a vacuum if it had an apparent mass less than the actual one by the mass of displaced fluid. Inversely, if one immerses a particle into a symmetrically arranged homogeneous fluid apart from its centre of symmetry, the particle and the fluid produce, at the centre of symmetry of the fluid, a gravitational field that would be produced in vacuo by a particle of the same size and shape but having apparent mass. Simple laboratory experiments, suitable to verify this inverse theorem, are described. On the other hand, the gravitational force between two particles in an infinite homogeneous fluid is reduced by a factor proportional to the product of their apparent masses which can be positive or negative. Two particles with opposite apparent masses repel each other. The results obtained imply corrections to vacuum of the order of (10–5–10–4) G of the gravitational constant,G, measured by the common laboratory methods. 相似文献
15.
《New Astronomy》2024
A very well-known property of close binary stars is that they usually rotate slowly than a similar type single star. Massive stars in close binary systems are supposed to experience an exchange of mass and angular momentum via mass transfer and tidal interaction, and thus the evolution of binary stars becomes more complex than that of individual stars. In recent times, it has become clear that a large number of massive stars interact with binary companions before they die. The observation also reveals that in close pairs the rotation tends to be synchronized with the orbital motion and the companions are naturally tempted to invoke tidal friction. We here introduce the effect of tidal angular momentum in the model of wind driven non-conservative mass transfer taking mass accretion rate as uniform with respect to time. To model the angular momentum evolution of a low mass main sequence companion star can be a challenging task. So, to make the present study more interesting, we have considered initial masses of the donor and gainer stars at the proximity of bottom-line main sequence stars and they are taken with lower angular momentum. We have produced a graphical profile of the rate of change of tidal angular momentum and the variation of tidal angular momentum with respect to time under the present consideration. 相似文献
16.
An obstacle to the asteroid mass determination lies in the difficulty in isolating the gravitational perturbation exerted by a single asteroid on the planets, being strongly correlated and mixed up with those of many other asteroids. This hindrance may be avoided by the method of analysis presented here: an asteroid mass is estimated in correspondence with its close encounters with Mars where the acceleration it induces on the planet can be sufficiently disentangled from those generated by the remaining asteroid masses to calculate. We test this technique in the analysis of range observations to Mars Global Surveyor and Mars Express performed from 1999 to 2007. For this purpose, we adopt the dynamical model of the planetary ephemeris INPOP06 (Fienga et al., 2008), which includes the gravitational influences of the 300 most perturbing asteroids of the Martian orbit. We obtain the solutions of 10 asteroid masses that have the largest effects on this orbit over the period examined: they are generally in good agreement with determinations recently published. 相似文献
17.
We study the entanglement entropy associated to the phonons generated via the Hawking mechanism of acoustic black holes in a Bose–Einsten condensate. The lowest energy allowed for the radiated phonons is found to be a function of space coordinate. Based this, we calculate the entanglement entropy, which contains three parts: a leading term, which is a constant of value 1/6, a logarithmic correction term and some series terms. We discuss the convergence of the series terms. 相似文献
18.
In this paper we compare the minimum masses of Schwarzschild black hole obtained from the generalized uncertainty principle and the Heisenberg uncertainty principle. Three minimum masses are obtained. The first two are the order of Planck mass which can be normally accepted. The last one based on Scardigli’s hypothesis and consideration is about M c ?1015 g～1020 M pl which may be problematic. Whether right or wrong, it needs the astronomical observations. 相似文献
19.
黄润乾 《中国天文和天体物理学报》1999,(2)
现今双星演化理论中,以子星的半径等于临界洛希瓣半径,作为双星中发生物质交换过程的判据,仅仅是一个为了将三维计算简化为一维计算而引入的近似判据．它在理论上是不严格的．本文给出了一个理论严格而又能一维计算的判据．并用新的判据和用子星半径等于临界洛希瓣半径的判据,对一个由９Ｍ和６Ｍ恒星组成的双星系统,进行了情况Ａ的演化计算（即物质交换过程发生在主星中心氢燃烧阶段）．结果证明,用新的判据时,双星中发生物质交换过程的起始时间提前,快速物质交换过程变短,平均物质交换率增大,但慢速物质交换过程变长．在物质交换过程结束时,主星和次星的质量、双星系统的轨道周期以及主星在赫罗图中的位置,都与采用子星半径等于相应洛希瓣半径作为判据的计算结果明显不同．这说明,发生物质交换过程的判据是否严格,对于双星演化的影响是不可忽略的． 相似文献
20.
We study the evolution of globular clusters with mass spectra under the influence of the steady Galactic tidal field, including the effects of velocity anisotropy. Similarly to single-mass models, velocity anisotropy develops as the cluster evolves, but the degree of anisotropy is much smaller than in isolated clusters. Except for very early epochs of the cluster evolution, the velocity distributions of nearly all mass components become tangentially anisotropic at the outer parts. We examine how the mass function (MF) changes in time. Specifically, we find that the power-law index of the MF decreases monotonically with the total mass of the cluster, in agreement with previous findings based on isotropic models or N -body studies. This is also consistent with the behaviour of the observed slopes of MFs for a limited number of clusters. We attempt to compare our results with multimass King models, although it is almost impossible to fit the entire density profiles for all mass components. When the MF is fixed, the central densities of individual components show significant differences between Fokker–Planck and King models. We obtain 'best-fitting' multimass King models, for which the central density of individual components as well as the total density distribution agrees with the Fokker–Planck models by adjusting the MF. The MFs obtained in this way closely resemble the MF within the half-mass radius of the Fokker–Planck result. Also, we find that the local MFs predicted by Fokker–Planck calculations vary more rapidly with radius than best-fitting multimass King models. The projected velocity profiles for anisotropic models show significant flattening toward the tidal radius compared with the isotropic model. This is caused by the fact that the tangential velocity dispersion becomes dominant at the outer parts. Such a behaviour of velocity profile appears to be consistent with the observed profiles of the collapsed cluster M15. 相似文献