Detection Of Gravitational Waves Research Articles

Gravitational Wave Signal Prediction Technique based on Advanced Seasonal-Trend decomposition using Loess

Abstract Gravitational wave (GW) analysis is attracting widespread attention as an emerging research field. As the presence of substantial noise in GW signals, and the characteristics of inspiral and merger stage are different, coupled with the sidelobe effect caused by window length, traditional time-frequency analysis methods face significant challenges in accurately analyzing the frequency variations of GW signals. This poses a major limitation in the precise analysis stage following GW detection. Therefore, we proposed a novel method of Seasonal-Trend decomposition using Loess with Multilayer Perceptron (STLMLP), for predicting and validating the accuracy and effectiveness of GW frequency variations. Experiment results on three noiseless GW templates demonstrate that STLMLP exhibits the adaptability and highest prediction accuracy for the dynamic frequency variations of GW signals compared to five state-of-the-art machine learning and deep learning methods. Furthermore, experiments conducted on three noisy actual GW data compared with the state-of-the-art method of Fourier-based synchrosqueezing transform (FSST) in the signal processing domain confirm that STLMLP maintains lower error in predicting frequency change over the whole duration of the actual noisy GW signals.

Quantum Technologies for the Einstein Telescope

Quantum technology is central to the operation of modern gravitational-wave detectors and will play crucial role in the success of next-generation observatories, such as the Einstein Telescope. There, quantum squeezed light will be utilized to suppress quantum noise across the entire detection band, a task that demands advancements in several areas of quantum technology. This review provides an introduction to the quantum technologies employed in gravitational-wave detection and explores in detail their properties, challenges, and the potential they hold for the Einstein Telescope.

Long-term Evolution of Sco X-1: Implications for the Current Spin Frequency and Ellipticity of the Neutron Star

Abstract Sco X-1 is the brightest observed extrasolar X-ray source, which is a neutron star (NS) low-mass X-ray binary (LMXB) and is thought to have a strong potential for continuous gravitational waves (CW) detection due to its high accretion rate and relative proximity. Here, we compute the long-term evolution of its parameters, particularly the NS spin frequency (ν) and the surface magnetic field (B), to probe its nature and its potential for CW detection. We find that Sco X-1 is an unusually young (∼7 × 106 yr) LMXB and constrain the current NS mass to ∼1.4–1.6 M ⊙. Our computations reveal a rapid B decay, with the maximum current value of ∼1.8 × 108 G, which can be useful to constrain the decay models. Note that the maximum current ν value is ∼550 Hz, implying that, unlike what is generally believed, a CW emission is not required to explain the current source properties. However, ν will exceed an observed cutoff frequency of ∼730 Hz, and perhaps even the NS breakup frequency, in the future without a CW emission. The minimum NS mass quadrupole moment (Q) to avoid this is ∼(2–3) × 1037 g cm2, corresponding to a CW strain of ∼10−26. Our estimation of current ν values can improve the CW search sensitivity.

Mass oscillations in superconducting junctions for gravitational wave emission and detection

Mass oscillations in superconducting junctions for gravitational wave emission and detection

Measuring remanent magnetic moment of test masses by a compound pendulum in a magnetic shielding room.

In space-borne gravitational wave detection, the remanent magnetic moment of test masses is one of the primary contributors to residual acceleration noise. During the ground test phase, precisely measuring the remanent magnetic moment of the test masses under an ultra-weak magnetic field is crucial for assessing its suitability for the space mission. In this work, we developed a compound pendulum apparatus within the magnetic shielding room, utilizing the pendulum's periodic motion to convert the remanent magnetic moment into a modulated magnetic field. The measurement resolution of remanent magnetic moment reaches a level of 0.2nAm2.

Next-Generation Gravitational Wave Detectors: Advancements, Challenges, and Scientific Potential

Abstract: Gravitational wave (GW) detection has revolutionized our understanding of the universe, opening a new observational window into astrophysical and cosmological phenomena. The next generation of GW detectors, such as the Einstein Telescope (ET), Cosmic Explorer (CE), and Laser Interferometer Space Antenna (LISA), promise unprecedented scientific discoveries. This review explores the advancements driving these detectors, the scientific potential they offer, and the challenges associated with their development, including technological, financial, and environmental constraints. Furthermore, it highlights their role in probing the early universe, testing fundamental physics, and advancing multi-messenger astronomy. These projects herald a new era of discovery, paving the way for transformative insights into the nature of space, time, and matter.

Exploring the Role of Gravitational Waves in the Evolution of the Universe: Tracing Origins in Overlapping Gravitational Waves

Gravitational wave detections have revolutionized astrophysics, enabling observations of cosmic phenomena beyond electromagnetic waves. These new observation techniques allow us to see through dense regions where light can’t provide enough information, such as black hole mergers. However, the transient noise and the overlapping signals pose a challenge, significantly hindering the trace of the origin. This study investigates potential overlapping circumstances as well as solutions for addressing them. One proposed solution to resolve overlapping signals is the comparison of detected frequencies using a Bayesian Inference and template matching technique. Possible approaches include improving sensitivity and signal processing techniques in current detectors such as LIGO and VIRGO. Space-based detectors like LISA, Taiji, and TianQin are set to launch, but techniques to interpret the signals are still under development. This methodology allows astrophysicists to distinguish high strain and provide a pre-collision stage. Furthermore, extensive research into gravitational waves and signal characteristics can improve signal interpretation and advance our understanding of the evolution of the universe. The improvement holds a potential benefit in examining the properties of astrophysical sources, particularly in differentiating the overlapping gravitational background, and thus will improve multi-messenger astronomy.

Singlet-doublet fermionic dark matter in gauge theory of baryons

We are considering a minimal U(1)B extension of the Standard Model (SM) by promoting the baryon number as a local gauge symmetry to accommodate a stable dark matter (DM) candidate. The gauge theory of baryons induces non-trivial triangle gauge anomalies, and we provide a simple anomaly-free solution by adding three exotic fermions. A scalar S spontaneously breaks the U(1)B symmetry, leaving behind a discrete Z2 symmetry that ensures the stability of the lightest exotic fermion originally introduced to cancel the triangle gauge anomalies. Scenarios with weakly interacting DM candidates having non-zero hypercharge usually face stringent constraints from experimental bounds on the DM spin-independent direct-detection (SIDD) cross-section. In this work, we consider a two-component singlet-doublet fermionic dark matter scenario, which significantly relaxes the constraints from bounds on the DM SIDD cross-section for suppressed single-doublet mixing. We show that the model offers a viable parameter space for a cosmologically consistent DM candidate that can be probed through direct detection searches, collider experiments, and gravitational wave (GW) experiments.

Reliability evaluation of the grabbing, positioning, and release mechanism for gravitational wave detection

Predicting reliability is an essential part of the design phase for ensuring mission success. In the realm of gravitational wave detection, the integrity and dependability of the Grabbing, Positioning, and Release Mechanism (GPRM) are paramount for its effective space-based deployment. However, predicting reliability of a complex mechanical system like the GPRM during the design phase poses significant challenges due to the harsh and variable conditions of the space environment. This paper addresses these challenges by proposing a reliability evaluation method that combines the stochastic and degradation characteristics of the GPRM, according to which both randomness of the stud position and the degradation of the piezoelectric coefficient are considered. Failure criteria are established based on mission performance indicators, and the Kaplan-Meier estimator is used to analyze the mechanism reliability of the GPRM over time. The result predicts that the reliability of the GPRM is around 0.8 after 107 operating cycles. This finding demonstrates that our proposed method is an effective approach for evaluating reliability, offering valuable insights for ensuring the long-term performance and successful operation of precision mechanisms.

Performance comparison of two telescope configurations for backscattered light in space gravitational wave detection

Performance comparison of two telescope configurations for backscattered light in space gravitational wave detection

Optical design of gravitational wave detection telescope based on suppression of tilt to length coupling noise

Spaceborne telescopes are vital components in space-based gravitational wave (GW) detection observatories, utilized for receiving and emitting laser signals to facilitate heterodyne interferometric displacement measurements. The coupling of wavefront aberrations with tilt-to-length (TTL) noise in space gravitational wave telescopes is a pivotal factor impacting measurement accuracy and warrants thorough attention. This research endeavors to achieve a telescope design with high optical path stability by reducing non-geometric TTL coupling noise, aiming to keep such noise beneath the threshold of 0.025 nm/µrad. We propose a method utilizing tolerance analysis to generate random wavefront samples and have conducted an analysis of the impact of various types of aberrations on TTL coupling noise. Research indicates that constraining the proportion of coma in the telescope's wavefront aberrations can lead to rapid convergence of TTL noise, thereby successfully guiding the improved design of the telescope. When the pointing jitter angle of the telescope is within the range of ±300µrad, the output RMS wavefront error is controlled within λ/300 (λ=1064 nm), and the coupling coefficient has shown a significant decrease compared to the initial design. The method proposed offers a reliable tool for the suppression of TTL noise in space-based GW detection.

On the "direct detection" of gravitational waves.

In this paper, I provide an account of direct (vs. indirect) detection in gravitational-wave astrophysics. In doing so, I highlight the epistemic considerations that lurk behind existing debates over the application of the term "direct". According to my analysis, there is an epistemically significant distinction between direct and indirect detections in this context. Roughly, our justification for trusting a direct detection depends mainly on the reliability of instruments that are under our control, rather than on the reliability of our models of separate target systems. In contrast, indirect detections rely on confidence in such models. Overall, this paper solves a puzzle about what counts as a "direct" detection of gravitational waves in a way that is true to scientific usage, and (more importantly) both philosophically precise and epistemically perspicuous. Having done so, this paper provides a foundation for a broader project of analyzing the epistemic situation of (gravitational-wave) astrophysics.

Polarization modes of gravitational waves in scalar-tensor-Rastall theory

Rastall theory, originally introduced in 1972, suggests a violation of the usual conservation law. We consider two generalizations of Rastall theory: Brans–Dicke–Rastall theory and the newly established scalar-tensor-Rastall theory, the latter being a further generalization of the former. The field equations in these two generalized theories are studied across different parameter spaces, and the polarization modes of gravitational waves, as a key focus, are subsequently investigated. The results show that the polarization modes of gravitational waves in Brans–Dicke–Rastall theory are the same as those in Brans–Dicke theory; specifically, both theories exhibit the plus, cross, and breathing modes. However, in scalar-tensor-Rastall theory, the polarization modes of gravitational waves depend on the parameter space of the theory. Particularly, over a broad range of the parameter space, regardless of some special values of the parameters, it allows only two tensor modes, just as in general relativity, without introducing any additional degrees of freedom. This indicates that Rastall theory offers a novel approach to constructing modified gravity theories that propagate only two tensor degrees of freedom. In the remaining regions of the parameter space, there is also one scalar mode in addition to the two tensor modes. The scalar mode can be either a mixture of the breathing and longitudinal modes or just a pure breathing mode, depending on the parameter space. These results will play a crucial role in constraining the theoretical parameters through future gravitational wave detection projects, such as LISA, Taiji, and TianQin.

Dual-Loop Charge Management for Space-Based Gravitational Wave Detection

In space-based gravitational wave detection missions, inertial sensors act as the inertial reference, requiring the test mass (TM) to maintain exceptionally low residual acceleration noise. High-energy particles, cosmic rays, and ion pumps during ground tests can quickly lead to charge accumulation on the TM surface, necessitating a charge management system to regulate surface charges. To manage the TM surface potential, this paper develops a mathematical model of the charge management system using established ultraviolet (UV) discharge simulation methods. The model describes how photoelectron emission or absorption on the TM surface varies with UV light-emitting diodes (LEDs) power and bias voltage. For the first time, a dual-loop control method is implemented for charge control, highlighting its practical significance. The controller precisely regulates the TM surface potential and residual charges to specified values, achieving a control accuracy of 1.1×106e, meeting the stringent requirements of space-based gravitational wave detection missions. This approach offers a closed-loop charge management solution and provides valuable insights for designing future charge management systems.

Progress in the development of space inertial sensor for TianQin project

The TianQin project is a space gravitational wave detection program proposed by China, imposing strict requirements on inertial sensors. This paper introduces the basic principle and development progress of the TianQin project inertial sensor. At present, key technologies such as test mass, capacitance displacement sensing, and charge management have been developed, with some performance exceeding requirements. Ground-based test systems utilizing torsion pendulums have initially investigated the patch effect, magnetic field effect, residual gas damping, and temperature gradient effect. The inertial sensor is currently undergoing system integration and ground performance tests, and will be tested on TQ-2.

Stellar population and metal production in AGN discs

ABSTRACT As gravitational wave detections increase the number of observed compact binaries (consisting of neutron stars or blacks), we begin to probe the different conditions producing these binaries. Most studies of compact remnant formation focus either on stellar collapse from the evolution of field binary stars in gas-free environments or on the formation of stars in clusters where dynamical interactions capture the compact objects, forming binaries. But a third scenario exists. In this paper, we study the fate of massive stars formed, accrete gas, and evolve in the dense discs surrounding supermassive black holes. We calculate the explosions produced and compact objects formed by the collapse of these massive stars. Nucleosynthetic yields may provide an ideal, directly observable, diagnostic of the formation and fate of these stars in active galactic nuclei. We present a first study of the explosive yields from these stars, comparing these yields with the observed nucleosynthetic signatures in the discs around supermassive stars with quasars. We show that, even though these stars tend to form black holes, their rapid rotation leads to discs that can eject a considerable amount of iron during the collapse of the star. The nucleosynthetic yields from these stars can produce constraints on the number of systems formed in this manner, but further work is needed to exploit variations from the initial models presented in this paper.

Atom interferometer as a freely falling clock for time-dilation measurements

Abstract Light-pulse atom interferometers based on single-photon transitions are a promising tool for gravitational-wave detection in the mid-frequency band and the search for ultralight dark-matter fields. Here we present a novel measurement scheme that enables their use as freely falling clocks directly measuring relativistic time-dilation effects. The proposal is particularly timely because it can be implemented with no additional requirements in Fermilab’s MAGIS-100 experiment or even in the 10 m prototypes that are expected to start operating very soon. This will allow the unprecedented measurement of gravitational time dilation in a local experiment with freely falling atoms, which is beyond reach even for the best atomic-fountain clocks based on microwave transitions. The results are supported by a comprehensive treatment of relativistic effects in this kind of interferometer as well as a detailed analysis of the main systematic effects. Furthermore, the theoretical methods developed here constitute a valuable tool for modelling light-pulse atom interferometers based on single-photon transitions in general.

Gravitational Wave and Quantum Graviton Interferometer Arm Detection of Gravitons

This paper explores the quantum and classical descriptions of gravitational wave detection in interferometers like LIGO. We demonstrate that a graviton scattering and quantum optics model succeeds in explaining the observed arm displacements, while the classical gravitational wave approach and a quantum graviton energy method also successfully predict the correct results. We provide a detailed analysis of why the quantum graviton energy approach succeeds, highlighting the importance of collective behavior and the quantum–classical correspondence in gravitational wave physics. Our findings contribute to the ongoing discussion about the quantum nature of gravity and its observable effects in macroscopic physics.

Research on Mass Center Identification for Gravitational Wave Detection Spacecraft with Guaranteed Laser Link Pointing Accuracy

The deviation of the center of mass of a gravitational wave detection satellite from its calibrated position can severely impact the accuracy of gravitational wave detection. Therefore, there is an urgent need to develop effective identification methods to achieve precise center of mass identification while ensuring the alignment of the laser link. To address this issue, this paper proposes a method for the center of mass identification of gravitational wave detection spacecraft that ensures the pointing accuracy of the laser link. A study on the relative attitude dynamics modeling of gravitational wave detection spacecraft is conducted, and the conditions for small, periodic spacecraft maneuvers that maintain laser link alignment are analyzed. A high-precision, high-stability center of mass identification method based on dual-model data fusion is proposed and simulated. The results show that this method can maintain the alignment precision of the laser interferometer arms within 10 nrad, while achieving a center of mass identification accuracy of 25 μm. Compared to existing methods, this method improves the identification accuracy by an order of magnitude, demonstrating its feasibility for application in gravitational wave detection constellations. It provides theoretical support for the center of mass identification of gravitational wave detection spacecraft.

Design and alignment of a space gravitational wave detection telescope based on aberration scale control.

Regulating the proportion of low-order aberrations within total aberrations can effectively alter the tilt-to-length (TTL) coupling noise in a space gravitational wave telescope. Nevertheless, the low-order aberration ratio is disrupted during the actual manufacturing of the telescope. To address this issue, we analyzed the impacts of wavefront errors and low-order aberration proportions on the TTL coupling noise, determined the design requirements, and designed a 400 mm-aperture space gravitational wave telescope optical system. Subsequently, a nonlinear function matrix between the misalignment and Zernike polynomial coefficients was constructed, and an accurate alignment algorithm based on the low-order aberration ratio was proposed to predict the misalignment of optical systems. Finally, 500 sets of misalignment files were randomly generated using the Monte Carlo method, and the degree of misalignment of the optical system was predicted through the algorithm. The results indicated that 90.6% of the misalignment files satisfied the design requirements after a single alignment, whereas the remaining files satisfied the requirements after two alignments. This study offers an effective scheme for designing and installing a space gravitational wave telescope.