On the conditions of stability of mechanical equilibrium <ob usloviyakh ustoychivosti mekhanicheskogo ravnovesiya<
Nonadiabatic criterion for stability of mechanical equilibrium of gas layer in gravitational field
GRAVITATIONAL FIELD↗
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Relativistic equations for spherical gravitational collapse with escaping neutrinos.
Relativistic equations for gravitational collapse of sphere of ideal fluid with subsequent outward neutrino flux
GRAVITATIONAL COLLAPSE↗
Collisional and dynamical processes in moon and planet formation
The collisional and dynamical processes in moon and planet formation are discussed. A hydrodynamic code of collision calculations, the orbital element changes due to gravitational scattering, a validation of the mass shifting algorithm, a theory of rotations, and the origin of asteroids are studied. A numerical model of planet growth is discussed and a methodology to evaluate the rate at which megaregolith increases its depth as a function of total accumulate number of impacts on an initially smooth, coherent surface is described.
Source record↗
Cosmological variation of G and the solar luminosity
Teller's analysis of the effects of a varying gravitational constant G on the past solar luminosity is reexamined. It is shown that if Newtonian gravitation is viewed as a nonrelativistic limit of Einstein's theory, there exists (1) a constraint between G and the total mass M of the sun and (2) a change in the radiative energy density-temperature relation, which were not included in Teller's analysis and which change his result from L is about G to the 7th power (found to be unacceptable) to L is about constant, independently of how G might vary with time.
Canuto, V.↗
Possible effects of organelle charge and density on cell metabolism
A system of perception and transduction involving the gravity-induced asymmetric distribution of a plant growth hormone is studied. A theory is constructed which assumes that the perception of the gravitational stimulus involved a perturbation of the plant's bioelectric field and that the transduction of the stimulus involved voltage-gating of hormone movement from the plant's vascular tissue into the hormone responsive growing tissue. Particular attention is focused on the barriers to indole-3-acetic acid (IAA) transport from the seed to the mesocotyl cortex, the protoinhibition of IAA movement from the endosperm to the shoot, the effects of the gravitational stimulus on the movement of IAA from the kernel to the shoot, electrochemical gating as a target for the gravity stimulus, and the gravity sensing mechanism.
Bandurski, Robert S.↗
Proceedings of the Workshop on the Scientific Applications of Clocks in Space
The Workshop on Scientific Applications of Clocks in space was held to bring together scientists and technologists interested in applications of ultrastable clocks for test of fundamental theories, and for other science investigations. Time and frequency are the most precisely determined of all physical parameters, and thus are the required tools for performing the most sensitive tests of physical theories. Space affords the opportunity to make measurement, parameters inaccessible on Earth, and enables some of the most original and sensitive tests of fundamental theories. In the past few years, new developments in clock technologies have pointed to the opportunity for flying ultrastable clocks in support of science investigations of space missions. This development coincides with the new NASA paradigm for space flights, which relies on frequent, low-cost missions in place of the traditional infrequent and high-cost missions. The heightened interest in clocks in space is further advanced by new theoretical developments in various fields. For example, recent developments in certain Grand Unified Theory formalisms have vastly increased interest in fundamental tests of gravitation physics with clocks. The workshop included sessions on all related science including relativity and gravitational physics, cosmology, orbital dynamics, radio science, geodynamics, and GPS science and others, as well as a session on advanced clock technology.
Maleki, Lute↗
Resource Letter GrW-1: Gravitational Waves
The phenomenon of gravitational radiation was one of the first predictions of Einstein's general theory of relativity. Progress in understanding this radiation theoretically was slow at first, owing to the difficulty of the nonlinear field equations and the subtleties of their physical effects. The experimental side of this subject also has taken a long time to develop, with efforts at detection severely challenged by the extreme weakness of the waves impinging on the Earth. However, as the 21st century begins, observations of the gravitational waves from astrophysical sources such as black holes, neutron stars, and stellar collapse are expected to open a new window on the universe. Vigorous experimental programs centered on ground-based detectors are being carried out worldwide, and a space-based detector is in the planning stages. On the theoretical side, much effort is being expended to produce robust models of the astrophysical sources and accurate calculations of the waveforms they produce. In this Resource Letter, a set of basic references will be presented first, to provide a general introduction to and overview of the literature in this field. The focus then will shift to highlighting key resources in more specialized areas at the forefront of current research.
White, Nicholas E.↗
Gravitational waves from first-order cosmological phase transitions
A first-order cosmological phase transition that proceeds through the nucleation and collision of true-vacuum bubbles is a potent source of gravitational radiation. Possibilities for such include first-order inflation, grand-unified-theory-symmetry breaking, and electroweak-symmetry breaking. We have calculated gravity-wave production from the collision of two scalar-field vacuum bubbles, and, using an approximation based upon these results, from the collision of 20 to 30 vacuum bubbles. We present estimates of the relic background of gravitational waves produced by a first-order phase transition.
Kosowsky, Arthur↗
A recursively formulated first-order semianalytic artificial satellite theory based on the generalized method of averaging. Volume 2: The explicit development of the first-order averaged equations of motion and for the nonspherical gravitational and nonresonant third-body perturbations
For abstract, see N78-28147.
Mcclain, W. D.↗
One-dimensional periodic flows with a shock transition - Application to the density wave theory of spiral structure
The problem of one-dimensional gas flow through a sinusoidal gravitational potential with a series of equally spaced shock fronts is considered. For time-independent and spatially periodic flows, an integral equation relates the flow velocity to the gravitational potential and source functions of energy and momentum densities. It is suggested that this problem simulates some of the dynamical effects of the azimuthal flow on a parcel of gas at a fixed radius in a galactic disk that supports a spiral density wave structure. It omits the radial motions. In this context, a typical azimuthal velocity across a spiral arm is specified and the resultant source functions are obtained. The implications of this calculation suggest heating of the gaseous disk by O and B stars behind the shock front, and subsequent interarm cooling is a plausible mechanism for maintaining the periodic cycling of the gaseous component of the galactic disk.
Bogdan, T. J.↗
Life Sciences and Space Research 25 (1). Gravitational Biology; Interdisciplinary Scientific Commission F of the COSPAR Plenary Meeting, 29th, Washington, DC, Aug. 28-Sep. 5, 1992
The conference includes papers describing theories and models of cell biology in microgravity and weightlessness; experimental research on cellular responses to altered gravity in plants and animals, natural and simulated; graviresponses in plants; gravitational effects in developmental biology; mechanisms of gravisensing; effects on animals and humans; and educational programs in Space Life Sciences.
Cogoli, A.↗
Tests of General Relativity with Stellar-Mass Black Hole Binaries Observed by LISA
We consider the observation of stellar-mass black holes binaries with the Laser Interferometer Space Antenna(LISA). Preliminary results based on Fisher information matrix analyses have suggested that gravitational waves from those sources could be very sensitive to possible deviations from the theory of general relativity (GR) andfrom the strong equivalence principle during the low-frequency binary inspiral. We perform a full Markov Chain Monte Carlo Bayesian analysis to quantify the sensitivity of these signals to two phenomenological modifications of GR, namely a putative gravitational dipole emission and a non-zero mass for the graviton, properly accounting for the detector’s response. Moreover, we consider a scenario where those sources could be observed also with Earth-based detectors, which should measure the coalescence time with precision better than 1 ms. This constraint on the coalescence time further improves the bounds that we can set on those phenomenological deviations from GR. We show that tests of dipole radiation and the graviton’s mass should improve respectively by seven and half an order(s) of magnitude over current bounds. Finally, we discuss under which conditions one may claim the detection of a modification to General Relativity.
Alexandre Toubiana↗
Spiral structure and star formation. I - Formation mechanisms and mean free paths
The wide variety of optical appearances observed in spiral galaxies has encouraged the growth of two theoretical approaches to explain the spiral patterns exhibited by such young objects as OB associations, giant H II regions, and dark dust lanes. These approaches are related to the density wave theory of spiral structure and 'stochastic, self-propagating star formation'. Levinson and Roberts (1981) tried to reconcile these two theoretical approaches, and considered a disk filled with discrete gas clouds. The present investigation is concerned with refinements and extensions of the model of Levinson and Roberts. Attention is given to gravitational forces and dynamical propagation, cloud-cloud collisions, supernova interactions, computational models, a theory concerning the interactions of the gas cloud and stellar association systems, the time evolution of the gas cloud-stellar association systems, and aspects of collisionally triggered star formation.
Roberts, W. W., Jr.↗
On long range effects in the motion of artificial satellites.
Halphen method and a resonance theory for determining long range effects of moon, sun and earth gravitational field irregularity in motion of artificial satellites
SATELLITE ORBIT↗
Quantum nondemolition measurements
The article describes new electronic techniques required for quantum nondemolition measurements and the theory underlying them. Consideration is given to resonant-bar gravitational-wave antennas. Position measurements are discussed along with energy measurements and back-action-evading measurements. Thermal noise in oscillators and amplifiers is outlined. Prospects for stroboscopic measurements are emphasized.
Braginskii, V. B.↗
On neutron star structure and the millisecond pulsar
The recently discovered millisecond pulsar (PSR1937-214) is observed to be rotating close to the limit of dynamical instability for a neutron star. Despite its extremely rapid rotation, measurements of the period derivative put a stringent upper limit on the energy loss from gravitational radiation, thus requiring that the quadrupole moment be quite small. The pulsar must also be rotating below the critical frequency at which its equilibrium configuration would become non-axisymmetric, since the lifetime of this configuration against decay by gravitational radiation is very short. This critical frequency, given by the theory of rotating ellipsoids, imposes a restriction on the rotation rate more severe than the break-up frequency and may be used to set a lower limit, rho 2 x 10 to the 14th power g/cu cm, on the density of the star. If the mass is 0.5 - 1.5 solar mass, several of the stiffer neutron star equations of state may be ruled out, and the radius should be less than 16 km. The condition for axisymmetry also imposes an upper limit on the rotation rate to which neutron stars may be spun up by accretion disks in binary systems, a model recently proposed for the evolution of the millisecond pulsar.
Harding, A. K.↗
Annihilation physics of exotic galactic dark matter particles
Various theoretical arguments make exotic heavy neutral weakly interacting fermions, particularly those predicted by supersymmetry theory, attractive candidates for making up the large amount of unseen gravitating mass in galactic halos. Such particles can annihilate with each other, producing secondary particles of cosmic-ray energies, among which are antiprotons, positrons, neutrinos, and gamma-rays. Spectra and fluxes of these annihilation products can be calculated, partly by making use of positron electron collider data and quantum chromodynamic models of particle production derived therefrom. These spectra may provide detectable signatures of exotic particle remnants of the big bang.
Stecker, F. W.↗
Resonance excitation of spiral density waves in a gaseous disk. II - A nonlinear theory and application to the 3 kiloparsec arm
The present nonlinear theory of spiral density waves in a thin, viscous, self-gravitating gaseous disk views the waves as generated near the Lindblad resonance by periodic disturbances through an excitation mechanism. The suggestion of Yuan (1984), that either a minor oval distortion or an uneven distribution of mass in the center can excite a spiral density wave whose radial velocity and mass concentration are in excellent agreement with observations of the 3 kpc arm of the Galaxy, is confirmed. Reliable results are obtained for nonlinear density waves either in a gaseous disk or in the gas components of a galactic disk.
Yuan, Chi↗