On the behavior of an oscillator clock near the singularity of a gravitational field

In 1975 Møller tried to show that the general relativistic concept of standard time or proper time would lose its physical meaning in the vicinity of singularities of a gravitational field [1]. His treatment of a classical harmonic oscillator clock falling into a singularity is checked in the present paper and is found to be insufficient to prove the above statement. A relativistic clock model is given to ensure the reasonable physical meaning of proper time.     

Kinematical and gravitational analysis of the rocket-borne clock experiment by Vessot and Levine using the revised Robertson's test theory of special relativity

The kinematic aspects of the rocket-borne clock experiment by Vessot and Levine are analyzed with the revised Robertson's test theory of special relativity (Found. Phys. 14, 625 (1984)). Besides the expected time-dilation, it is found that the intermediate steps of this experiment yield in principle Michelson-Morley type information (a relation between longitudinal and transverse length contractions) in the third order of the velocities involved, but no relativity-of-simultaneity related effects.The flat space-time test theory induces a family of spherically symmetric line elements that become the Schwarzschild line element in the relativistic case and also in theabinito rest frame of the theory. These line elements represent the same space-time manifold, but pertain in a one-to-one correspondence to the different flat space-time coordinate transformations of the test theory. The conserved energy is related to the family of local energies in the tangent plane. No deviations from the orthodoxy appear at the pertinent levels of approximation. Hence the unexplained residuals of the Vessot-Levine experiment are not due in obvious ways to kinematic and gravitational frequency shifts caused by deviations of the real coordinate transformations from the Lorentz transformations.This work was started while the author was at Departamento de Fisica, Facultad Experimental de Ciencias, Universidad del Zulia, Maracaibo, Venezuela. It was completed at the Department of Physics, Utah State University, Logan, Utah 83422.     

引力、引力波和引力波的探测

简要地回顾了引力和引力波概念的由来,以及人们为探测引力波所作的各种努力．     

Using gravitational lenses to detect gravitational waves

Gravitational lenses could be used to detect gravitational waves, because a gravitational wave affects the travel-time of a light ray. In a gravitational lens, this effect produces time-delays between the different images. Thus the bending of light, which was the first experimental confirmation of Einstein's theory, can be used to search for gravitational waves, which are the most poorly confirmed aspect of that same theory. Applying this method to the gravitational lens 0957+561 gives new upper bounds on the amplitude of low-frequency gravitational waves in the universe, and new limits on the energy-density during an early inflationary phase.This Essay received the First Award from the Gravity Research Foundation, 1990-Ed.     

The gravitational faraday rotation for cylindrical gravitational solitons

By using cylindrical soliton solutions, the nonlinear behavior of gravitational waves in vacuum is studied in terms of a rotation of the polarization vector between two independent modes. This effect was emphasized by Piran, Safier, and Stark as a gravitational analogue of the Faraday rotation. The polarization of the soliton wave is calculated, and it is found that the+mode which was dominant near the axis of symmetry is fully converted to the×mode at some interaction region and then the disturbance propagating along a light cone like a gravitational wave pulse contains both polarizations.     

Can quantum gravitational forces stop gravitational collapse?

We consider, in lowest order of the gravitational coupling constant G, the gravitational potential between two neutrons. As we have previously pointed out [1],the quantum (including spin) contributions to the gravitational field dominate for distances smaller than the Compton wavelength of the neutron. At such distances the gravitational force between two neutrons may be repulsive. In particular, the gravitational forces which are analogous to the familiar Darwin and Fermi forces of quantum electrodynamics are capable of stopping gravitational collapse. Our discussion is within the framework of Einstein's theory, but on a microscopic level. We conclude that gravitational collapse may be halted without the necessity of extending Einstein's theory à la Cartan or otherwise.     

光钟

时间标准的研究在人类生活和科学探索中有着举足轻重的地位.文章简要介绍了时间的基本单位“秒”定义的几次重要发展与变迁,重点介绍了光钟的工作原理、关键部件、研究进展和光钟对“秒”定义未来发展的重要性.     

Conformally invariant gravitational waves in a modified gravitational theory

International Journal of Theoretical Physics - An attempt is made to obtain a conformally invariant gravitational wave equation in an isotropic background universe by modifying the Einstein field...     

Stochastic gravitational wave background due to gravitational wave memory

Gravitational wave memory is an important prediction of general relativity, which has not been detected yet. Amounts of memory events can form a stochastic gravitational wave memory background. Here we find that memory background can be described as a Brownian motion in the condition that the observation time is longer than the averaged time interval between two successive memory events. We investigate, for the first time, the memory background of binary black hole coalescences. We only consider...     

Equivalence principle and gravitational redshift

We investigate leading order deviations from general relativity that violate the Einstein equivalence principle in the gravitational standard model extension. We show that redshift experiments based on matter waves and clock comparisons are equivalent to one another. Consideration of torsion balance tests, along with matter-wave, microwave, optical, and M?ssbauer clock tests, yields comprehensive limits on spin-independent Einstein equivalence principle-violating standard model extension terms at the 10(-6) level.     

Extended supersymmetry and gravitational instantons

Methods of extended supersymmetry are used to construct explicitly an instanton solution of the Euclidian Einstein equations in empty space.Translated fromIzvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 18–21, June, 1989.     

Unified gravitational and Yang-Mills fields

We unify the gravitational and Yang-Mills fields by extending the diffeomorphisms in (N=4+n)-dimensional space-time to a larger group, called the conservation group. This is the largest group of coordinate transformations under which conservation laws are covariant statements. We present two theories that are invariant under the conservation group. Both theories have field equations that imply the validity of Einstein's equations for general relativity with the stress-energy tensor of a non-Abelian Yang-Mills field (with massive quanta) and associated currents. Both provide a geometrical foundation for string theory and admit solutions that describe the direct product of a compactn-dimensional space and flat four-dimensional space-time. One of the theories requires that the cosmological constant shall vanish. The conservation group symmetry is so large that there is reason to believe the theories are finite or renormalizable.     

Scalar field and gravitational instability

We study monopole perturbations of spherically symmetric scalar-vacuum and scalar-electrovacuum fields in general relativity and reduce the problem to a one-dimensional Schrödinger-like equation with a certain effective potential. Imposing certain boundary conditions, we select physically meaningful perturbations. Some of them grow exponentially and we conclude that the background system is unstable.     

Symmetry breaking and gravitational interaction

A scalar field Lagrangian is considered in the curved space-time to which a Hamiltonian determining nonzero vacuum field value is added. The initial Lagrangian can be expressed as a sum of Lagrangians for the constant scalar field component and perturbation. The first Lagrangian can be considered as a Lagrangian for the Einstein gravitational field in vacuum. The problem of renormalization of the constant scalar field component is investigated. It is demonstrated that in the case of conformal relation of the scalar field to the space-time curvature, there exists a unique value of the scalar space curvature for which the field can be considered constant (field perturbations do not result in renormalization of the constant component). This curvature value determines the unique value of the equilibrium nuclide density. A correlation of the examined Lagrangian parameters with the integral parameters of the Solar system is discussed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 18–34, July, 2006.     

Classical and quantum gravitational collapse

The quantization of a homogeneous isotropic closed Friedmann model filled with an ideal fluid is discussed within the framework of a geometrodynamical approach.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 81–86, May, 1977.The authors wish to express their deep indebtedness to B. A. Lysov and A. V. Borisov for their valuable help in the writing of this paper.     

Twistor spinors and gravitational instantons

We construct a complete Riemannian metric on the four-dimensional vector space ⁴ which carries a two-dimensional space of twistor spinor with common zero point. This metric is half-conformally flat but not conformally flat. The construction uses a conformal completion at infinity of theEguchi-Hanson metric on the exterior of a closed ball in ⁴.     

Zitterbewegung and gravitational Berry phase

Berry phases mix states of positive and negative energy in the propagation of fermions and bosons in external gravitational and electromagnetic fields and generate Zitterbewegung oscillations. The results are valid in any reference frame and to any order of approximation in the metric deviation.     

Electromagnetic and gravitational synchrotron radiation

A brief survey of the theory of synchrotron radiation (SR) is presented, with particular attention to quantum effects in the SR spectrum. The inaccuracy of the recent paper by Latal and Erber, considering quantum corrections to the classical SR spectrum, is pointed out. Some mechanisms of generation of gravitational radiation arealso discussed: gravitational SR, creation of gravitons in annihilation processes, and plasma generation of gravitational waves.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 46–53, February, 1980.