Signals from SN 1987A in Amaldi-Weber antennas as the possible detection of scalar gravitational waves

An equation is obtained for the cross section of a metal Weber cylinder for scalar gravitational waves, which are possible within the framework of the field theory of gravitation. It is shown that the signals detected by the Amaldi and Weber antennas during the explosion of supernova SN 1987A can be interpreted as the result of the action of scalar gravitational waves on solid-state detectors. The required energy of the gravitational waves is about 1 M_⊙c². Together with the observed excess (about 1 %) of gravitational radiation from the binary system containing the pulsar PSR 1913+16, the signals from SN 1987A are the second piece of observational evidence for the actual existence of scalar gravitational waves. The present-day, third-generation, solid-state antennas are capable of detecting scalar waves from events like SN 1987A at a distance up to 5 Mpc. The expected level of the signal from SN 19931 is about 7 mK. An experimental test of the longitudinal nature of scalar waves is possible using interferometric antennas based on free masses. Translated from Astrofizika, Vol. 40, No. 3, pp. 377–389, August, 1997.     

On upper limits for gravitational radiation

A procedure with a Bayesan approach for calculating upper limits to gravitational wave bursts from coincidence experiments with multiple detectors is described, where the detection efficiency for small signals is taken into consideration. The Bayesan approach to the upper limit estimation is confronted with the unified approach for the case when no events are observed in presence of a non-zero background.     

Neutrino bursts and gravitational waves experiments

Several experiments have been performed in many countries to observe gravitational waves or neutrino bursts. Since their simultaneous emission may occur in stellar collapses, we evaluate the effect of neutrino bursts on gravitational wave antennas and suggest the usefulness of a time correlation among the different detectors.     

Gravitational radiation from differentially rotating and oscillating white dwarfs

We examine the possible emission of gravitational waves from white dwarfs undergoing self-similar oscillations driven by the energy released during relaxation of their differential rotation. Two distributions of the initial angular momentum are considered. It is assumed that 1% of the energy dissipated by a rotating white dwarf is converted into the energy of self-similar oscillations and, therefore, into gravitational radiation. The relative amplitude of the gravitational radiation from an isolated white dwarf at a distance of 50 pc is found to be less than 10⁻²⁷. The emission from the galactic population of white dwarfs may create a background which overlaps the random cosmological background of gravitational radiation for the improved decihertz detectors currently being proposed. __________ Translated from Astrofizika, Vol. 49, No. 2, pp. 231–242 (May 2006).     

红外背景的畸变

本文研究了引力透镜和富星系团在宇宙中作为一种分布,对红外背景畸变的统计效应。其中包括富系团的热电子对红外背景畸变的Sunyaev-Zel’dovich效应,以及引力透镜对红外背景畸变的引力效应。本文给出了z=4范围内的红外背景的总畸变,其结果是:Sunyaev-Zel’-dovich效应为:(△T_r)/T_r～10~(-2)—10~(-3),纯引力效应为(△T_r)/T_r～10~(-3)—10~(-4)。     

Gravitational Radiation of Relativistic <Emphasis Type="Italic">n</Emphasis> = 1 Polytropes

The gravitational radiation of n = 1 polytropes undergoing quasiradial pulsations is examined. The intensity of the gravitational radiation and the gravitational wave amplitudes are calculated for polytropic models of white dwarfs and neutron stars when the energy of rotation of the object serves as the source of the radiated energy. Calculations of h₀ show that objects with a polytropic equation of state can describe the expected gravitational radiation from white dwarfs and neutron stars. The gravitational radiation of polytropic models of galactic nuclei and quasars is also examined. These objects can create a high enough background of gravitational radiation at frequencies of 10^-8–10^-11 Hz for gravitational wave detectors operating in this frequency range. __________ Translated from Astrofizika, Vol. 48, No. 4, pp. 603–612 (November 2005).     

基于Shapelets基函数的引力透镜质量重构方法

引力透镜效应是探测星系团物质分布的有效方法之一.目前,利用引力透镜数据重构星系团质量分布的主流方法可以分为两大类,即参数法和非参数法.在实际研究工作中,受限于质量模型假设和计算分辨率等方面的影响,现有的重构算法仍有诸多亟需解决的问题.基于Shapelets基函数的引力透镜质量重构方法通过基函数来实现引力透镜质量重构,使用Shapelets基函数分解引力透镜势,以引力透镜中多重像的位置和背景星系椭率畸变为限制条件来迭代求解基函数系数从而得到透镜体的质量分布.通过拟合一个模拟的NFW (Navarro,Frenk and White)透镜系统测试了新方法的可行性,结果表明新方法可以在整体上重构出透镜体的质量分布,并拟合出接近真实的源位置,能够为星系团质量测量提供一套灵活且高效的重构算法.     

Bimetric formulation of scalar-tensor theories of gravitation and conservation laws

The scalar-tensor theories are formulated against a flat background space-time. Expressions for various energy-momentum tensors of the gravitational field and relations between them are obtained. Integral conservation laws are examined and formulas for four-momentum and angular momentum tensor of the gravitational field together with the matrix are derived.Translated from Astrofizika, Vol. 37, No. 1, pp. 147–160, January–March, 1994.     

Simulating a stochastic background of gravitational waves from neutron star formation at cosmological distances

We develop a temporal simulation of the potentially detectable gravitational wave background from neutron star formation at cosmological distances. By using a recent model for the evolving star formation rate, we investigate the statistical distribution of gravitational wave amplitudes due to supernovae that result in neutron star formation in the Einstein–de Sitter cosmology. We find that the gravitational wave amplitude distribution in our frame is highly skewed, with skewness related to the distribution of sources, and that the potentially detectable gravitational wave strain is dominated by sources at a redshift of     . Time traces of the simulation, using selected waveforms, are presented graphically and are also made available as web-based audio files. The method developed can readily be extended to different cosmologies, as well as to incorporate other waveforms and source types. This type of simulation will be useful in testing and optimizing detection strategies for gravitational wave backgrounds due to various types of individually undetectable astrophysical sources.     

高阶引力理论及其在星系旋转 曲线中应用的可能性

介绍了建立高阶引力理论（该理论用以修正爱因斯坦广义相对论）的物理背景,并讨论了暗物质问题。对几种主要高阶引力理论及其解作了评述,并尝试在不必假定暗物质存在的情况下,用高阶引力理论解决有关星系旋转曲线的困难。但令人遗憾的是,至今还没有一个理论取得完全的成功。指出了解决这一问题面临的困难,并建议寻找新的高阶引力理论。     

Fluctations in the cosmic microwave background arising from low-frequency gravitational radiation

Intense low-frequency intergalactic gravitational radiation with wave lengths λ smaller than the HUBBLE distance λ_H ≌ 3000 (100/H₀) Mpc but not exceedingly small compared to λ_H. generates anisotropies in the microwave background radiation. One contribution results from the local wave field and produces mainly a quadrupole-type temperature variation on the sky. Available data on large-scale microwave fluctuations do not exclude appreciable amounts of gravitational background radiation in the Megaparsec wave band. A more sensitive test is provided by a second far-field contribution, which has a small angular scale. Its amplitude depends strongly on the ratio of the (present) rest mass density to the HUBBLE constant, if a cosmological origin of the blackbody radiation is assumed. In a low-density universe, pre-galactic COMPTON scattering of the blackbody radiation is not able to reduce the fluctuations caused by the low-frequency gravitational wave field. The recent small-scale data by PARIJSKIJ would allow only small amplitudes of gravitational waves with an energy density significantly below the critical cosmological density. On the other hand, in a high-density universe, the small angular scale fluctuation in the blackbody radiation is completely damped out, and a gravitational radiation cosmos reaching the critical density is admitted. Independent of the matter density, the data by PARIJSKIJ would confine gravitational background radiation to insignificant amplitudes if a discrete source model for the origin of the microwave background has to be assumed.     

Die Ausbreitung der skalaren Kugelwellen bis zur 2. Náherungsordnung im Gravitationsfeld mit Quadrupolstruktur

By means of the perturbation expansion scheme with respect to the gravitational constant we give a retarded solution of the covariant wave equation for the potential of a free massless scalar field in an axially symmetric gravitational background field of a point mass with a quadrupole moment. For the zeroth order solution we choose a spherical symmetric wave as an ansatz. Our results show that far from the source the spherical symmetric second order wave tail is effectively generated by the loss of mass, caused by gravitational radiation, and that all the other second order tail terms are compensable by first order multipole moments corresponding to a change of the boundary conditions.     

On gravitational radiation from binary systems

We discuss gravitational radiation from a neutral mass particle within a bound orbit in the background Schwarzschild metric. We compare the power loss of gravitational radiation according to this formalism with the heuristic quadrupole radiation formula as applied to a binary system. There are evidence and compelling reasons to believe that the quadrupole formula is valid even in a fairly strong gravitational field, although its fully consistent analytical derivation is not yet known. In particular, we emphasize that the application of the quadrupole formula to the binary pulsar system PSR 1913+16 as well as other binary pulsars, which are weakly bound by gravity, is well justified.     

引力波理论和实验的新进展

引力波的存在是爱因斯坦在广义相对论理论中提出的一个重要预言．由于目前技术水平的限制,无法在实验室产生足以被探测到的引力波,因此宇宙中大量的大质量剧烈活动的天体成为科学家研究引力波的首选,从而诞生了引力波天文学．引力波探测将开启研究宇宙的新窗口,是继电磁辐射、宇宙线和中微子探测后探索宇宙奥秘的又一重要手段,对天文学研究有着极为重要的意义.新一代应用了高灵敏度的迈克耳逊干涉仪装置的长基线引力波探测仪正在建造中．该综述从引力波理论出发,阐述了目前研究较多的可探测引力波源,给出了目前观测上的最新进展,并展望了今后的发展前景．     

The stochastic background of gravitational waves from neutron star formation at cosmological distances

We investigate the stochastic gravitational wave background that results from neutron star birth throughout the Universe. The neutron star birth rate, as a function of redshift, is calculated using an observation-based model for the evolving star formation rate, together with an estimate of the rate of core-collapse supernovae in the nearby Universe and an estimate of the neutron star/black hole branching ratio. Using three sample waveforms, based on numerical models of stellar core collapse by Zwerger & Müller, the spectral flux density, spectral strain, spectral energy density and duty cycle of the background have been computed. Our results show, contrary to recent claims, that the spectrum of the stochastic background clearly reflects the different physics in the core-collapse models. For a star formation model that is corrected for dust extinction, the neutron star formation rate throughout the Universe is high enough to result in a nearly continuous background of gravitational waves, with spectral features that can be related to emission mechanisms.     

Nonsingular cosmological model with background field in flat space-time theory of gravitation

A previously studied theory of gravitation in flat space-time is applied to homogeneous, isotropic cosmological models. In addition to radiation a two-component fluid model consisting of dust and of a background field is studied. This universe starts from a nonsingular state and expands for ever. The energy of radiation, of dust and of the background are emerged from the gravitational energy. Entropy is produced. The age of the universe is infinite measured in units of absolute time whereas the proper-time of the universe is finite. The sum of the density parameters of dust, of radiation and of the background field is about one. There is no flatness and no monopole problem.     

Gravitational lensing by stars in a galaxy halo: Theory of combined weak and strong scattering

The theory of gravitational lensing of background quasars by stars in the halo of a galaxy is considered. In the limiting case of small ‘optical depth’, only one star is close enough to the beam to cause strong scattering, and the effect of all the other stars is treated as a perturbation with both systematic and random components. The perturbation coming from weak scattering can increase the number of images and the amplification in those cases where the amplification is already high; such events are preferentially selected in flux limited observations. The theory is applicable to the apparent association of background quasars with foreground galaxies. A comparison with earlier work on the same problem is given. The relevance of these results to gravitational lensing by galaxies as perturbed by random inhomogeneities surrounding the ray path is also briefly discussed.     

Electromagnetic radiation from a source at the center of a static charged dust sphere

Using Maxwell equations in a background metric discovered by Bonnor, which describes the gravitational field generated by an optimally charged dust ball, we calculate the external radiation field from an electric dipole source at the center the ball. Possible applications to stellar mode 1 s are discussed in the conclusions.     

A solution of linearized Einstein field equations in vacuum used for the detection of the stochastic background of gravitational waves

A solution of linearized Einstein field equations in vacuum is given and discussed. First it is shown that, computing from our particular metric the linearized connections, the linearized Riemann tensor and the linearized Ricci tensor, the linearized Ricci tensor results equal to zero. Then the effect on test masses of our solution, which is a gravitational wave, is discussed. In our solution test masses have an apparent motion in the direction of propagation of the wave, while in the transverse direction they appear at rest. In this way it is possible to think that gravitational waves would be longitudinal waves, but, from careful investigation of this solution, it is shown that the tidal forces associated with gravitational waves act along the directions orthogonal to the direction of propagation of waves. The computation is first made in the long wavelengths approximation (wavelength much larger than the linear distances between test masses), then the analysis is generalized to all gravitational waves.

In the last sections of this paper it is shown that the frequency dependent angular pattern of interferometers can be obtained from our solution and the total signal seen from an interferometer for the stochastic background of gravitational waves is computed.