High-Frequency Gravitational Waves in Electromagnetic Waveguides

The interaction between a very-high-frequency gravitational wave (VHFGW) and an electromagnetic wave (EMW) in a rectangular waveguide is discussed in the weak field limit. The background EMW is assumed to be initially in the TE₁₀ mode along the waveguide. It is then shown that a VHFGW, having the same frequency and direction of propagation of the EMW, induces through the waveguide a TE mode with a frequency doubled when compared to the original EMW frequency. In that respect, the GW acts similar to a non-linear medium, giving rise to a Second Harmonic Generation (SHG) effect.     

Utilization of Electromagnetic Detector for Selection and Detection of High-Frequency Relic Gravitational Waves

It is shown that the coupling system between fractal membranes and a Gaussian beam passing through a static magnetic field has strong selection capability for the stochastic relic gravitational wave （GW） background. The relic GW components propagating along the positive direction of the symmetrical axis of the Gaussian beam might generate an optimal electromagnetic perturbation, while the perturbation produced by the relic GW components propagating along the negative and perpendicular directions to the symmetrical axis will be much less than the former, and the influence of the random fluctuation of the relic GWs to such effect can be neglected. The high-frequency relic GWs satisfying the parameters requirement （h - 10^-31 or larger）, frequency resonance and “direction coupling”, in principle, would be selectable and measurable in seconds.     

Phase and Polarization State of High-Frequency Relic Gravitational Waves

The displaying condition of strength, phase and polarization states of high-frequency relic gravitational waves （HFRGWs） in electromagnetic （EM） detecting systems is studied. It is shown that the displaying condition depends not only on the sensitivity of EM detecting systems and the amplitudes of HFRGWs, but also on the phase, the polarization states of HFRGWs and their matching to the EM detecting systems. In order to display simultaneously the strength, phase and polarization states of the resonant ＂monochromatic component＂ of HFRGWs, an important necessary condition is the utilization of two or more different EM detectors.     

引力波探测展望

早在1916年，爱因斯坦在发表广义相对论时就预言引力辐射的存在．但在初期，大多数人都怀疑引力波（Gravitational　Waves）仅仅是爱因斯坦提出的引力场方程的一个近似解…而没有实质的物理效应．直到1950年代末期，从理论上证明引力波是携带能量的并可以被探测到，引力波的存在才在理论上得到了充分的确认．广义相对论预言引力波的主要特性有：在真空中以光速传播；     

Electromagnetic Response of High-Frequency Gravitational Waves by Coupling Open Resonant Cavity

We present a new detecting scheme of high-frequency gravitational waves （HFGWs） in the GHz band, the scheme consists of a high-quality-factor open microwave cavity, a static magnetic field passing through the cavity and an electromagnetic （EM） normal mode stored in the cavity. It is found that under the resonant condition first- and second-order perturbation EM effects have almost the same detecting sensitivity to the HFGWs in the GHz band （h ～10^-26, v～5GHz）, but the former contains more information from the HFGWs. We also provide a very brief review for possible improving way of the sensitivity. This scheme would be highly complementary to other schemes of detecting the HFGWs.     

Optimization of the Electromagnetic (EM) Perturbative Effects Produced by High-Frequency Gravitational Waves

For the relic gravitational waves in high frequency band, we survey the electromagnetic resonance effect generated from the high frequency gravitational waves, which can be described in the transverse perturbative photon fluxes. Under the fixed tensor-scalar ratio r = 0.2, spectral index n _t = 0 and running index α _t = 0.01, we discuss several properties and quantity changes of the transverse perturbative photon fluxes, which can be improved significantly through setting the longitudinal magnetic component of background EM field in the standard gaussian form, and wave impedance analysis on the transverse direction. Through the theoretical calculation, the transverse perturbative photon fluxes can reach up to 10³ s ^?1 with some optimal parameters such as waist of EM field W ₀ = 0.05m, initial stochastic phase of gravitational waves δ = (0.21 + n)π(n = 0,1,2...). Furthermore the interference of the background transverse photon fluxes can be removed completely through establishing a suitable wave impedance function.     

Self-Action of Nonparaxial Few-Cycle Optical Waves in Dielectric Media

A mathematical model of evolution of the space–time spectra of nonparaxial few-cycle optical waves in isotropic dielectric media with an arbitrary dispersion of the refractive index and the inertialess third-order nonlinearity has been discussed. It has been shown that, at the self-focusing of a wave single-cycle at the input to a nonlinear medium into an optical filament with transverse dimensions comparable with the central radiation wavelength, the strength of the increased longitudinal component of its electric field can become larger than the initial longitudinal component by a factor of 7 and can be 18% of the transverse component of the input wave field. Errors of the calculations of the self-action of radiation with superwide time and spatial spectra within simplified mathematical models have been estimated.     

On Gravitational Nonmetricity Plane Waves in an Affine-Metric Space

Russian Physics Journal -     

On the Transverse Shift of the Reflection and Refract ion of Electromagnetic Waves on the Interface of Dielectric Media

Based on the transformation properties of a constrained system under the conformal group, we show that the transverse shift (TS) exists. Some mistakes in Ref [5] are corrected     

Gravitational Waves and the Conformal Transformation

We study the problem of the behaviour of cosmological gravitational waves under conformal transformations. In spite of the apparent triviality of this question, the informations we can obtain from gravitational waves in the so-called Einstein's and Jordan's frame are not the same, mainly with respect to the choice of the initial conditions and of graviton production. The only exception seems to occur in string cosmology due to the duality properties.     

On the Sub-Doppler Spectroscopy of Optically Excited Atoms in a Thin Gas Cell

This work continues a theoretical investigation of the capabilities of the well-known method based on using a monochromatic probe light beam in combination with optical pumping of atoms (molecules) of a rarefied-gas medium by a broadband radiation in a thin cell the diameter of which is much larger than its internal thickness. In contrast to calculations carried out in the previous publications on this method of spectroscopy, here, we consider the case of arbitrary values of pump intensity and thickness of a cylindrical gas cell. Thus, all the possible mechanisms and specificities of velocity selection of atoms in optically excited levels caused by transit-time relaxation of such atoms in gas cells of this kind are analyzed. Within the framework of this approach, sub-Doppler absorption resonances of the probe light beam corresponding to quantum transitions from the upper level excited by optical pumping are investigated. The obtained results can be used in high-resolution spectroscopy of atoms (molecules), as well as for laser-frequency stabilization to established narrow spectral resonances.     

On the Matter of the Gravitational Waves' Detection

The interaction of a gravitational wave (G.W.) with substances causes periodical changes of their density. These changes may be fixed either by means of piezocrystals (just as in Weber's arrangement [1], for example) or by means of the light scattering on the sound aroused by G.W. It is of great interest the utilization of substances' critical states as a detector; the large compressibility of the former affords the maximum of possible changes of their density in a definite gravitational field. They have discussed one kind of experiment in [4] (denoted here as I) in which the presence of the gravitational flow caused periodical changes of the freguency of the light scattered on the fluctuations of one of the components of the two – component solution in its critical state of stratification.     

Quantization of Gravitational Waves and Squeezing

The question whether gravitational waves are quantised or not can in principle be answered by the help of correlation measurements. If the gravitational waves are quantised and they are generated by the change of the background metrics then they can be squeezed. In a squeezed state there is a correlation between the phase of the wave and the quantum uctuations. It is proposed to analyse the data to be obtained by the gravitational detectors from the point of view of such correlations. Explicit formulae are derived for the squeezing parameters of the quantised gravitational waves. The head on collision of two identical black holes is analysed as a possible source of squeezed gravitational waves.     

On the Boltzmann Equation for Diffusively Excited Granular Media

We study the Boltzmann equation for a space-homogeneous gas of inelastic hard spheres, with a diffusive term representing a random background forcing. Under the assumption that the initial datum is a nonnegative L²(^N) function, with bounded mass and kinetic energy (second moment), we prove the existence of a solution to this model, which instantaneously becomes smooth and rapidly decaying. Under a weak additional assumption of bounded third moment, the solution is shown to be unique. We also establish the existence (but not uniqueness) of a stationary solution. In addition we show that the high-velocity tails of both the stationary and time-dependent particle distribution functions are overpopulated with respect to the Maxwellian distribution, as conjectured by previous authors, and we prove pointwise lower estimates for the solutions.     

Superenergy of Gravitational Waves in the Exact Theory

Gravitational waves and radiation in the exact theory are studied in a unique framework. The observer's point of view is introduced. Some results by Lichnerowicz are generalized and interpreted in terms of reference frames. This allows us to recognize the role played by the gravitational force field in the exact generalization of Bel's superenergy flux theorem. It is also possible to recover the usual concept of wave as energy transmission, by means of a suitable superenergy scalar.     

Numerical Relativity and the Discovery of Gravitational Waves

Solving Einstein's equations precisely for strong‐field gravitational systems is essential to determining the full physics content of gravitational wave detections. Without these solutions it is not possible to infer precise values for initial and final‐state system parameters. Obtaining these solutions requires extensive numerical simulations, as Einstein's equations governing these systems are much too difficult to solve analytically. These difficulties arise principally from the curved, non‐linear nature of spacetime in general relativity. Developing the numerical capabilities needed to produce reliable, efficient calculations has required a Herculean 50‐year effort involving hundreds of researchers using sophisticated physical insight, algorithm development, computational technique, and computers that are a billion times more capable than they were in 1964 when computations were first attempted. The purpose of this review is to give an accessible overview for non‐experts of the major developments that have made such dramatic progress possible.     

On the Properties of Stationary Distributions of Gravitational Vortex Fields and Continuous Media

Russian Physics Journal - Properties of an ideal self-gravitating fluid with a barotropic equation of state in the equilibrium configurations and its vortex physical fields have been studied within...