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We investigate the potential of neural-network based classifiers for discriminating gravitational wave bursts (GWBs) of a given canonical family (e.g. core-collapse supernova waveforms) from typical transient instrumental artifacts (glitches), in the data of a single detector. The further classification of glitches into typical sets is explored. In order to provide a proof of concept, we use the core-collapse supernova waveform catalog produced by H. Dimmelmeier and co-Workers, and the data base of glitches observed in laser interferometer gravitational wave observatory (LIGO) data maintained by P. Saulson and co-Workers to construct datasets of (windowed) transient waveforms (glitches and bursts) in additive (Gaussian and compound-Gaussian) noise with different signal-to-noise ratios (SNR). Principal component analysis (PCA) is next implemented for reducing data dimensionality, yielding results consistent with, and extending those in the literature. Then, a multilayer perceptron is trained by a backpropagation algorithm (MLP-BP) on a data subset, and used to classify the transients as glitch or burst. A Self-Organizing Map (SOM) architecture is finally used to classify the glitches. The glitch/burst discrimination and glitch classification abilities are gauged in terms of the related truth tables. Preliminary results suggest that the approach is effective and robust throughout the SNR range of practical interest. Perspective applications pertain both to distributed (network, multisensor) detection of GWBs, where some intelligence at the single node level can be introduced, and instrument diagnostics/optimization, where spurious transients can be identified, classified and hopefully traced back to their entry points.

The fields, created from quantum fluctuations during inflation era, are known to be in squeezed quantum states. And recent studies show that the Planck scale physics can have observable cosmological effects. We investigate here how the squeezed quantum states are influenced by the trans-Planckian cutoff which modifies the dispersion relation on subhorizon scales, and calculate the particle production at the end of the inflation.

We propose TS-like class of gravitational wave solutions in 4D Einstein gravity. TS1-like gravitational wave solution is analyzed in detail. On the axis, the gauge potential changes from a finite value to zero at t = τ. The spacetime on the axis approaches the flat one as t → ∞. It is found that by an appropriate parameter substitution and coordinate transformation TS-like gravitational wave solutions in 4D Einstein gravity may be obtained from TS solutions.

Gravity-induced quantum interference is an experiment that exhibits how a gravitational effect appears in quantum mechanics.¹ In this famous experiment, gravity was added to the system just classically. In our study, we will do the related calculations on a gravitational wave background. We will argue that the effect of gravitational wave would be detectable in this quantum mechanical effect.

Gravitational waves result from various spacetime-perturbing events which are due to various kinds of motions and changing distributions of mass. Most studies on the source of gravitational waves were derived from the dynamic character of two binary compacted massive objects such as black holes and neutron stars, therefore gravitational waves which originated from a single event source would be of interest. In this paper, we derive the stress–energy tensor (SET) of a braneworld wormhole and demonstrate how the bulk-induced gravitational waves influence the SET of the wormhole. Thus, this study not only suggests a single source of gravitational waves, but also proves the existence of higher dimensional space by providing a formulation, namely, the SET at the wormhole throat affected by the bulk-induced gravitational waves.

We are trying to make a hardware logic-circuit for pipelines of fast Fourier transformation (FFT) with a field programmable gate array (FPGA) for data analyses of an interferometric gravitational-wave detector. That FFT processor is connected to a personal computer (PC) through PCI bus and will increase the calculation speed of FFT which is the most time-consuming step for typical gravitational-wave analyses.

Thermal conductance and light scattering were measured for two bonded sapphire samples. A sample with adhesion free bonding (AFB) showed the same thermal conductivity as that of the bulk at cryogenic temperatures. In contrast, a finite thermal resistance was observed in the sample with hydroxide-catalysis bonding (HCB). Light scattering at λ = 488 nm from bonded region was about 10% larger than the bulk part and was about 800 ppm of an incident laser power for AFB sample.

An ultra-small vibration cryocooler system for a cryogenic interferometric gravitational wave detector has been developed. The system consists of a pulse tube cryocooler and a vibration-reduction system. Its vibration level was about 50 nm for the vertical direction at 1 Hz, which was three orders of magnitude smaller than that of an original pulse tube cryocooler.

The CLIO project in Japan consists of two kinds of interferometric detectors in a tunnel of Kamioka mine. One is a geophysical strain meter and the other one is a gravitational wave (GW) detector. The GW detector is called Cryogenic Laser Interferometer Observatory (CLIO). The characteristics of CLIO are the use of cryogenic to reduce the thermal noises and an underground site for low seismic vibration. CLIO is under construction, and installation of the first cryogenic system was completed in the autumn of 2004.

Advanced Virgo is the French–Italian second generation laser gravitational wave detector, successor of the Initial Virgo. This new interferometer keeps only the infrastructure of its predecessor and aims to be ten times more sensitive, with its first science run planned for 2017. This article gives an overview of the Advanced Virgo design and the technical choices behind it. Finally, the up-to-date progresses and the planned upgrade for the following years are detailed.

We consider two realistic models for a scale invariant extension of the standard model, which couples with a hidden non-Abelian gauge sector. At energies around TeV, the hidden sector becomes strongly interacting, thereby generating a robust energy scale, which is transferred to the standard model sector, triggering the electroweak symmetry breaking. At a finite temperature, i.e. in the early Universe, the generation of the robust energy scale appears as a strong first-order phase transition. We calculate the gravitational wave background spectrum for both models, which is produced by the first-order phase transition. We compare the results with the experimental sensitivity of LISA and DECIGO and find the gravitational wave signal may be detected at DECIGO.

We consider a relation between the Huygens Principle (HP) in gravity and the self-interaction force. We show that the self-force for an electric particle in the plane gravitational wave space-time has no tail term even the vector Green function does not obey the HP. The reason for this observation is that even vector potential does not obey the HP, the electromagnetic field does obey.

We review potential low-frequency gravitational-wave sources, which are expected to be detected by Taiji, a Chinese space-based gravitational-wave detector, estimate the detection rates of these gravitational-wave sources and present the parameter estimation of massive black hole binaries.

The “Taiji-1” satellite is a test satellite for the verification of those key technologies involved in the “Taiji Program in Space”, China’s space gravitational wave detection project; and the spacecraft drag-free control technology is one of its key technologies used to improve the microgravity level of spacecraft. Thus, a demand for a high-precision and continuously adjustable micronewton-level thrust has been proposed on the spacecraft micro-propulsion system. In allusion to such a task, a set of micronewton-level RF ion propulsion system was designed based on the principle of self-sustained discharge of RF plasma so as to conduct studies on the parameter optimization and engineering of RF ion thruster, and an engineering prototype of the micronewton-level continuously adjustable RF ion thruster was successfully developed to meet the design index requirements. The operating parameters have been solidified through further studies on the extreme operating conditions of the engineering prototype, and a series of ground simulation tests of space environment were successfully passed. The ground test and calibration experiment results of the micro-propulsion engineering prototype show that the engineering prototype has fully met the requirements of the Taiji-1 mission, thus having laid a solid foundation for the successful space verification of the key technologies for the “Taiji-1” satellite.

TAIJI-1 is a micro-gravity experiment spacecraft. The mission target is to verify some key techniques of the spacecraft payloads for the gravitational wave detection, which involve laser interferometer, gravity reference sensor, drag-free control technology, micro-propulsion system, super-quiescent spacecraft platform, etc. The verification of the data processing pipeline required by the next stage of TAIJI Program is also performed. In order to benefit from the joint observatory between TAIJI and LISA in the future, as a space mission, the science operations refer to the existing ESA and NASA standard models, which include the Mission Operations Center (MOC), the Science Operations Center (SOC), the Data Processing Center (DPC), etc. The data processing pipeline connects between SOC and DPC. The SOC obtains the level-0 data from MOC and DPC performs the data processing and distributes the level-2 and level-3 data to SOC. For TAIJI-1 mission, SOC and DPC are two subsystems, which are included into the named science application system (SAS). That is the one of the six-function systems, which operate Chinese space mission. MOC is relevant to the ground support system (GSS) and spacecraft control system, that are also the ones of six-function systems of Chinese space mission. The on-orbit experiment plannings are transported from SAS to GSS, that is similar to from SOC to MOC in NASA standard models. The computer construction and computer software are the basic elements of the SAS, that are constructed completely, before the TAIJI-1 was launched. After TAIJI-1 enters the orbit, the data processing pipeline begins to work and the experimental items of TAIJI-1 are performed in the pipeline. The basic functions, performances and optimization functions of the detection devices in the payloads are verified completely 3 months after launch. In the same time, the methods of data analysis and processing are also verified. As a result, the required indicators of key techniques of the spacecraft for the gravitational wave detection are justified. The data processing pipeline is also reasonable. The relevant codes for data analysis and processing will benefit the next stage of TAIJI Program.

We have investigated a model of colliding plain gravitational waves, proposed by Szekeres, whose structure of singularities is determined. We have evaluated a total energy of matter as a volume integral of the energy–momentum tensor (EMT), whose contributions arise only at these singularities. The total matter energy is conserved before a collision of two plane gravitational waves but decreases during the collision and becomes zero at the end of the collision. We thus interpret that this model of colliding plane gravitational waves is a space–time describing a pair annihilation of plan gravitational waves. We have also calculated a matter conserved charge proposed by the present author and his collaborators. The matter charge is indeed conserved but is zero due to a cancelation between two plain gravitational waves. This seems natural since nothing remains after a pair annihilation, and gives a hint on a physical interpretation of the conserved charge, which we call the gravitational charge. By modifying the space–time for the pair annihilation, we newly construct two types of a scattering plane gravitational wave and a pair creation of plane gravitational waves, and combining all, a Minkowski vacuum bottle, a Minkowski space–time surrounded by two moving plane gravitational waves.

We discuss, in this work, new aspects related to the emission of gravitational waves by neutron stars, which undergo a phase transition, from nuclear to quark matter, in its inner core. Such a phase transition would liberate around 10^52–53 erg of energy in the form of gravitational waves which, if detected, may shed some light in the structure of these compact objects and provide new insights on the equation of state of nuclear matter.

The success of LISA is dependent on the precision with which the test masses, the interferometer mirrors, can maintain pure geodesic motion. Their accumulation of charge from cosmic rays and solar wind particles can give rise to spurious Lorentz and Coulomb forces. Coherent Fourier components, which appear due to the time dependence of the amount of charge accrued, are estimated to exceed the acceleration noise target. The general forms of these signals are derived. It is shown that for typical parameter values, coherent signals with significant signal-to-noise ratios can result from Coulomb interactions, while the signal from Lorentz interactions is expected to fall below the instrumental noise target. In this description, the signals' peak magnitudes are shown to increase with decreasing frequency. Hence their impact may be greater for missions that aim to look for gravitational waves at frequencies below the nominal LISA band. It is expected that the accuracy with which these signals can be removed from the data will depend on deviations from the predictable temporal behavior of the parameters on which they are dependent. Methods to substantially decrease these signals for LISA are discussed.

We study the problem of all-sky search in reference to a continuous gravitational wave (CGW) whose wave-form is known in advance. We employ the concept of fitting factor and study the variation in the bank of search templates with different Earth azimuth at t = 0. We found that the number of search templates varies significantly. Hence, accordingly, the computational demand for the search may be reduced up to two orders by time shifting the data.

A pulsars spins down due to magnetic torque reducing its radius and increasing the central energy density. Some pulsars which are born with central densities close to the critical value of quark deconfinement may undergo a phase transition and suffer a structural re-arrangement. This process may excite oscillation modes and emit gravitational waves. We determine the rate of quark core formation in neutron stars using a realistic population synthesis code.