Tang Meng-xi

Positive definite problem of energy density and radiative energy flux for pulse cylindrical gravitational wave

By using the general expressions of energy-momentum pseudo-tensor of the cylindrical gravitational waves (GW) given by Rosen and Virbhadra in Cartesian coordinates, the concrete forms of energy density and radiative energy flux of the pulse cylindrical GW are obtained. Their physical properties, suitable range and asymptotic behaviour are considered. It is found that: For the region in which space radial coordinates to origin are greater than the pulse width of the pulse cylindrical GW, the energy density and radiative energy flux of the outward travelling pulse cylindrical GW propagating along a light-cone are positive definite. However, for the region in which the space radial coordinates are less than the pulse width, there is no guarantee for the positive definite property of the radiative energy flux of the outward travelling wave. Moreover, we show that the asymptotic behaviour of the energy and energy flux densities of the pulse cylindrical GW and that of the Riemann curvature tensor have good self-consistancy in space-like, time-like and null infinity regions.

Perturbed Effect of the Gravitational Wave Produced by Microwave Electromagnetic Cavity on Detecting Electromagnetic Field

Perturbed effect of high-frequency gravitational radiation produced by microwave electromagnetic (EM) cavity on static detecting EM field is investigated, and corresponding perturbation solutions have been given. It is found that the gravitational wave (GW) beam propagating along symmetric axis of the cavity is purely +type polarized in transverse traceless coordinate system, and it can make the static EM field generate a cumulative perturbed effect which is proportional to the time. For the gravitational radiation wave beams propagating along other directions, they are usually mixed radiation of + and × type polarization. Quality factor of the cavity plays a key role in interaction strength of the GW with the detecting EM field.

A recent coincidence experiment of gravitational waves with long baseline

The results of coincidence experiment which was carried out in the whole month of April, 1985 by two gravitational wave detectors in stanford and in Guangzhou are presented. It is found that up to sensitivity of h 10-16 the number of coincident events did not excess the number expected statistically.

A New Ultra-low Frequency Passive Vertical Vibration Isolation System

A new ultra-low frequency passive vertical vibration isolation system is constructed by connecting the torsion spring isolator with a reverse pendulum. The theoretical analysis shows that the new system can achieve a much longer resonant period and have a smaller size than the current torsion spring isolators with the same geometric parameters.

Determination of the period of a torsion pendulum by the fitting method in real time

A phenomenological study on the fitting method in real time has been done, and the method was applied to process and analyze the extensive data of a long period torsion pendulum used to determine Newtonian gravitational constant G. The result shows that the fitting method in real time is effective to determine the period of a torsion pendulum with a relative precision of 10-5 orders.

Exact (3+1)-Dimensional, 2-Soliton Solutions to the Einstein Gravitational Field Equation

A set of exact (3+1)-dimensional cylindrically symmetric 2-soliton solutions with three arbitrary functions to the Einstein gravitational field equation is found. Their physical properties, such as nontriviality, propagation and positive definiteness of energy density, are discussed.

A GROUP OF EXACT (3+1) DIMENSIONAL CYLINDRICALLY SYMMETRIC WAVE SOLUTIONS TO THE EINSTEIN GRAVITATIONAL FIELD EQUATION

Starting with the diagonal spacetime metric tensor, the Einstein gravitational field equation is solved, and a set of exact (3 + 1) dimensional cylindrically symmetric wave solutions with two arbitrary functions are found. In these solutions all nonvanishing components of spacetime metric tensor are varying with the same propagating factor (ct-z) while the waves are travelling along z axis. The physical picture and the condition of positive energy density of the wave solutions are discussed.

High frequency gravitational wave of a composite toroidal electromagnetic resonant system

Starting with the Einstein equation of weak gravitational field, a new scheme of generating high frequency gravitational wave by composite toroidal electromagnetic resonant system is discussed. The system is a composite toroidal electromagnetic resonant cavity consisting of a vacuum and a dielectric regions. In the focal region of the cavity under the condition of allowable ohmic losses in the cavity walls, the amplitude of the standing gravitational wave is almost two orders of magnitude higher than that in usual cavity with the same volume. A concrete numerical calculation shows that a composite toroidal electromagnetic resonant system with a volume 2 × 108 cm3 could generate the standing gravitational wave with an amplitude h = 10-33, wavelength λg = 40 cm in its focal region. This is comparable to the typical order of magnitude of several astrophysical sources, and it would be displayed by electromagnetic detection due to very high frequency.