Detection Of Gravitational Waves Research Articles

Stable configuration design for libration point gravitational wave observatory

The Sun-Earth L2 libration point configuration is one of the options for space-based gravitational wave detection. Long-term configuration stability is crucial for high-precision measurements, challenged by the strong nonlinear dynamics of the Sun-Earth three-body system. This paper proposes an efficient design method and determines the feasible parameter domain for the libration point gravitational wave observatory. First, the dynamic model for the libration point configuration is established, and the stability indexes are defined. The sensitive parameters that affect the relative geometric configuration are discussed and the phase angle is found to be the key factor. Then, an efficient design method is proposed, and the procedure is divided into two steps. The phase angle of the Earth phase offset orbit and the libration point configuration are optimized successively. Finally, the proposed method is applied to the LAGRANGE mission concept. The results show that the three stability indexes decrease by 59%, 42% and 23%, respectively. Moreover, a mapping between configuration parameters and stability indexes is established. The feasible parameter domain for the stable libration point configuration is discussed. The feasible amplitudes domain in the x and z directions of the libration point orbit should be less than 6200 km and 42000 km, respectively, to guarantee configuration stability. This research could provide a reference for the stable design and implementation of gravitational wave detection missions utilizing libration point configuration in the future.

Higgs inflation via a metastable standard model potential, generalised renormalisation frame prescriptions and predictions for primordial gravitational waves

Higgs Inflation via a metastable Standard Model Higgs Potential is possible if the effective Planck mass in the Jordan frame increases after inflation ends. Here we consider the predictions of this model independently of the dynamics responsible for the Planck mass transition. The classical predictions are the same as for conventional Higgs Inflation. The quantum corrections are dependent upon the conformal frame in which the effective potential is calculated. We generalise beyond the usual Prescription I and II renormalisation frame choices to include intermediate frames characterised by a parameter α. We find that the model predicts a well-defined correlation between the values of the scalar spectral index ns and tensor-to-scalar ratio r. For values of ns varying between the 2-σ Planck observational limits, we find that r varies between 0.002 and 0.005 as ns increases, compared to the classical prediction of 0.003. Therefore significantly larger or smaller values of r are possible, which are correlated with larger or smaller values of ns . In addition, the model can be compatible with the larger values of ns predicted by Early Dark Energy solutions to the Hubble tension, with correspondingly larger values of r. The model can be tested via the detection of primordial gravitational waves by the next generation of CMB polarisation experiments.

Searching for the Highest-z Dual Active Galactic Nuclei in the Deepest Chandra Surveys

We present an analysis searching for dual active galactic nuclei (AGN) among 62 high-redshift (2.5 < z < 3.5) X-ray sources selected from the X-UDS, AEGIS-XD, CDF-S, and COSMOS-Legacy Chandra surveys. We aim to quantify the frequency of dual AGN in the high-redshift Universe, which holds implications for black hole merger timescales and low-frequency gravitational wave detection rates. We analyze each X-ray source using BAYMAX, an analysis tool that calculates the Bayes factor for whether a given archival Chandra AGN is more likely a single or dual point source. We find no strong evidence for dual AGN in any individual source in our sample. We increase our sensitivity to search for dual AGN across the sample by comparing our measured distribution of Bayes factors to that expected from a sample composed entirely of single point sources and find no evidence for dual AGN in the sample distribution. Although our analysis utilizes one of the largest Chandra catalogs of high-z X-ray point sources available to study, the findings remain limited by the modest number of sources observed at the highest spatial resolution with Chandra and the typical count rates of the detected sources. Our nondetection allows us to place an upper limit on the X-ray dual AGN fraction at 2.5 < z < 3.5 of 4.8% at the 95% confidence level. Expanding substantially on these results at X-ray wavelengths will require future surveys spanning larger sky areas and extending to fainter fluxes than has been possible with Chandra. We illustrate the potential of the AXIS mission concept in this regard.

Einstein–Podolsky–Rosen conditional squeezing for next generation Gravitational-Wave detectors

Frequency-dependent squeezing (FDS) represents a well established way to address quantum noise (QN) in Gravitational-Wave (GW) Earth-based detectors, such as LIGO, Virgo, and KAGRA. This technique is realized with the use of an external detuned optical resonator, the filter cavity. The experiment we present here is a table-top prototype that will probe a cheaper, more compact and more flexible strategy for broadband QN reduction (Ma et al., 2017). This scheme is based on two-mode Einstein–Podolsky–Rosen (EPR) entangled squeezed light, and it works without any filter cavity. The EPR-entangled beams will propagate in a small-scale suspended interferometer with high-finesse arm-cavities. This experiment aims at validating the EPR conditional squeezing at audio frequencies, suited for GW detection, implementing also innovative optical techniques.

Compact advanced pure tilt actuator for testing tilt-to-length coupling in space-based gravitational wave detection

Tilt-to-length (TTL) coupling, caused by the jitter of test masses or satellites, is a major noise source in space-based gravitational wave detection. Calibrating and suppressing TTL coupling noise at the sub-nanometer level is essential. A key challenge in current ground-based TTL coupling testing is the residual translational movement of the tilt actuator. This paper presents the development of a compact advanced pure tilt actuator (APTA) specifically designed for testing TTL coupling. The APTA enables precise tilt motion, monitored by a four-beam interferometer measuring the displacement of attached retroreflectors. Detailed theoretical models and experimental setups are given. Experimental results demonstrate that the APTA test bed can achieve sub-nanometer-level TTL coupling calibration. Additionally, a typical test-mass interferometer tested by the APTA test bed demonstrated that the imaging system effectively suppresses TTL coupling errors. The TTL coupling coefficients were reduced from over ±30 μm/rad to within ±5 μm/rad across a range of ±200 μrad. The APTA test bed offers a compact, high-precision solution for ground-based TTL coupling tests and has the potential for broader application in related experimental setups.

ENTROPY OF GRAVITATIONAL WAVES

Gravitational waves (GWs), the propagating perturbations within the structure of spacetime, provide a unique window into the dynamics of massive celestial objects and their cataclysmic events such as binary black hole (BBH), black hole – neutron star, binary neutron star (BNS) merger. While the detection and analysis of GWs have significantly advanced our understanding of the universe, the exploration of their information content, specifically their entropy, is not well studied and remains an intriguing avenue of research. This article presents an application of the concept of entropy to GWs and its implications for astrophysics. By using masses of the detected GW sources provided by open-source Gravitational Wave Open Science Center (GWOSC) and the PyCBC library, we generated GWs using different models and approximations. Specifically, we employed three different waveform models: IMRPhenomPv3, IMRPhenomPv2_NRTidal, and IMRPhenomXPHM. After generating GWs with different models we investigated the relationship between entropy and the masses of GW sources. Besides varying values in different models, entropy nearly exponentially decreases while the total mass of the systems providing those GWs increases. Additionally, different waveform models demonstrated varying levels of entropy. This study opens avenues for further research on the underlying physics of GWs and their detection and classification methods.

Analysis of laser interference backward stray light based on TianQin space gravitational wave detection

Analysis of laser interference backward stray light based on TianQin space gravitational wave detection

Inferring Binary Properties from Gravitational-Wave Signals

This review provides a conceptual and technical survey of methods for parameter estimation of gravitational-wave signals in ground-based interferometers such as Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo. We introduce the framework of Bayesian inference and provide an overview of models for the generation and detection of gravitational waves from compact binary mergers, focusing on the essential features that are observable in the signals. Within the traditional likelihood-based paradigm, we describe various approaches for enhancing the efficiency and robustness of parameter inference. This includes techniques for accelerating likelihood evaluations, such as heterodyne/relative binning, reduced-order quadrature, multibanding, and interpolation. We also cover methods to simplify the analysis to improve convergence, via reparameterization, importance sampling, and marginalization. We end with a discussion of recent developments in the application of likelihood-free (simulation-based) inference methods to gravitational-wave data analysis.

Experimental demonstration of bi-directional laser ranging and data communication for space gravitational wave detection

In this study, we designed ranging parameters and refined a loop filtering algorithm to solve the problem of parameter compatibility with the phasemeter and low ranging accuracy under bidirectional communication conditions. This enables the ranging and communication system to be integrated directly into the phasemeter as an auxiliary module. Experimental results compare fiber measurement lengths under different clock sources, indicating that the system achieves an ranging accuracy of 82.1 cm with an rms error of 9.14 cm. Additionally, the data communication rate reaches 19.5 kbps with a bit error rate below 10−6, all while ensuring that the implementation of the laser ranging and data communication system utilizes only 1% of the optical power to avoid introducing excessive phase noise to the scientific interferometer.

Pushing the boundaries of gravitational wave detection

Broadband reduction of quantum noise should accelerate discovery

Listening to dark sirens from gravitational waves : Combined effects of fifth force, ultralight particle radiation, and eccentricity

We analyse the orbital period decay in compact binary systems influenced by a fifth force and ultralight particle radiation, considering a general eccentric Keplerian orbit. The analysis provides constraints on the axion decay constant when orbital period decay involves axionic fifth force and axion radiation. The bound on axion coupling improves by an order of magnitude for high eccentricity binaries like the Hulse–Taylor binary. These bounds become stronger when considering both axion mediation and radiation. We also derive constraints on the strengths of the fifth force and radiation from GW170817 by measuring the Chirp mass, which depends on initial eccentricity. The coalescence time increases with higher initial eccentricity compared to the gravity-only scenario, highlighting the importance of accurately selecting initial eccentricity for setting bounds on fifth force searches in precision gravitational wave detection. Additionally, we provide model-independent estimates for dark matter capture by a binary system. The derived constraints can be further strengthened with the use of second and third generation gravitational wave detectors.

Charging and Discharging Modeling of Inertial Sensors Based on Ultraviolet Charge Management

Inertial sensors act as inertial references in space gravitational wave detection missions, necessitating that their internal test mass (TM) maintains minimal residual acceleration noise. High-energy particles and cosmic rays in space, along with ion pumps in ground-based torsion pendulum experiments, can cause charge accumulation on the TM surface, leading to increased residual acceleration noise. Consequently, a charge management system was introduced to control the TM’s charge. The complex light path propagation within the electrode housing (EH) makes the TM’s charging and discharging process difficult to theoretically calculate and fully simulate. To address this issue, we propose a simulation method for charging and discharging inertial sensors within ultraviolet (UV) charge management systems. This method innovatively considers the impact of photoelectron emission angle and the TM’s position offset from symmetry on performance. The method also simulates charging and discharging rates over time under conditions of symmetry and preliminarily examines factors affecting the TM’s equilibrium potential. Simulation results indicate that this method effectively models the charge management system’s operation, providing a valuable reference for system design.

Superluminal propagation of light in a atomic medium

We manipulated and adjusted the absorption, dispersion, group index, and group velocity in a sodium atomic medium by controlling the strength and collective phase of the driving fields. The group index in these regions is calculated to be [Formula: see text]250,000. The group velocity [Formula: see text] in these locations is measured to be [Formula: see text][Formula: see text]m/s. An investigation is conducted on a negative delay of [Formula: see text]s in the sodium medium. The presence of negative delay and negative group velocity indicates the occurrence of superluminal propagation of light pulses within the medium. The negative group index is increased from [Formula: see text] to [Formula: see text], and the negative delay time is increased from [Formula: see text]s to [Formula: see text]s, with the driving field [Formula: see text] having a Rabi frequency. The work presented in this paper has substantial implications for the fields of gravitational wave detection, radar technology, and temporal cloaks.

The Evolution of Massive Binary Stars

Massive stars play a major role in the evolution of their host galaxies and serve as important probes of the distant Universe. It has been established that the majority of massive stars reside in close binaries and interact with their companion stars during their lifetimes. Such interactions drastically alter their life cycles and complicate our understanding of their evolution, but are also responsible for the production of interesting and exotic interaction products. ▪Extensive observation campaigns with well-understood detection sensitivities have enabled the conversion of observed properties into intrinsic characteristics, facilitating a direct comparison to theory.▪Studies of large samples of massive stars in our Galaxy and the Magellanic Clouds have unveiled new types of interaction products, providing critical constraints on the mass transfer phase and the formation of compact objects.▪The direct detection of gravitational waves has revolutionized the study of stellar mass compact objects, providing a new window to study massive star evolution. Their formation processes are, however, still unclear. The known sample of compact object mergers will increase by orders of magnitude in the coming decade, which is vastly outgrowing the number of stellar-mass compact objects detected through electromagnetic radiation.

Gravitational wave signal extraction against non-stationary instrumental noises with deep neural network

Sapce-borne gravitational wave antennas, such as LISA and LISA-like mission (Taiji and Tianqin), will offer novel perspectives for exploring our Universe while introduce new challenges, especially in data analysis. Aside from the known challenges like high parameter space dimension, superposition of large number of signals etc., gravitational wave detections in space would be more seriously affected by anomalies or non-stationarities in the science measurements. Considering the three types of foreseeable non-stationarities including data gaps, transients (glitches), and time-varying noise auto-correlations, which may come from routine maintenance or unexpected disturbances during science operations, we developed a deep learning model for accurate signal extractions confronted with such anomalous scenarios. Our model exhibits the same performance as the current state-of-the-art models do for the ideal and anomaly free scenario, while shows remarkable adaptability in extractions of coalescing massive black hole binary signal against all three types of non-stationarities and even their mixtures. This also provide new explorations into the robustness studies of deep learning models for data processing in space-borne gravitational wave missions.

Study on temperature noise suppression characteristics of passive thermal control materials in gravitational wave detection

Study on temperature noise suppression characteristics of passive thermal control materials in gravitational wave detection

Dual-barrier detector design improves chances of gravitational wave detection

An antimony-based Type II superlattice with a dual-barrier structure minimizes dark-current background noise in detected photocurrents.

Feasibility of ultrarelativistic bubbles in SMEFT

A first order electroweak phase transition probes physics beyond the Standard Model on multiple frontiers and therefore is of immense interest for theoretical exploration. We conduct a model-independent study of the effects of relevant dimension 6 and dimension 8 operators, of the Standard Model effective field theory, on electroweak phase transition. We use a thermally corrected and renormalization group improved potential and study its impact on nucleation temperature. We then outline bubble dynamics that lead to ultrarelativistic bubble wall velocities which are mainly motivated from the viewpoint of gravitational wave detection. We highlight the ranges of the Wilson coefficients that give rise to such bubble wall velocities and predict gravitational wave spectra generated by such transitions which can be tested in future experiments. Published by the American Physical Society 2024

Clock noise evaluation of space-based gravitational wave detectors based on time-delay interferometry

The heterodyne measurements are adopted in space-based gravitational wave detectors to detect gravitational wave signals in the millihertz range. Due to the difficulty in maintaining the equal distance between these spacecrafts in the detector, laser phase noise is a main noise in the detection process, so time-delay interferometry combination is adopted to eliminate this noise by synthesizing virtual equal arm interferometry. However, when conducting heterodyne laser interferometry measurements in space-based gravitational wave detection, clock noise is also introduced into the measurement, but the analytical results of clock noise have been ignored in previous studies. Based on time-delay interferometry combination, we analyze the impact of clock noise and provide analytical results of the total noise in various data combinations. Through this result, we evaluate the required clock accuracy of 10−16 for the gravitational wave detector when clock noise is not reduction, so the analytical result can more intuitively reflect how the clock noise effects the sensitivity of the detector.

Low dark current Sb-based short-wavelength infrared photodetector

We have theoretically and experimentally demonstrated the feasibility of achieving ultra-low dark current in CpBnn type detectors based on a double-barrier InAs/GaSb/AlSb type-II superlattice. By employing a structure that separates the absorption region and depletion region, the diffusion, recombination, tunneling, and surface dark currents of the photodetector (PD) have been suppressed. Experimental validation has shown that a detector with a diameter of 500 µm at a bias voltage of −0.5 V exhibits a dark current density of 2.5 × 10−6 A/cm2 at the operating temperature of 300 K. The development of PD with low dark current has paved the way for applications with high demands for low noise in the fields of gravitational wave detection and astronomical observation.