Detection Of Gravitational Waves Research Articles

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.

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 disks

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 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 disks 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 disks around supermassive stars with quasars. We show that, even though these stars tend to form black holes, their rapid rotation leads to disks 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.

Low-noise laser intensity noise evaluation system at Hz frequency band for ground-based gravitational wave detection

The direct detection of gravitational waves has opened a new window for understanding the universe and trailblazed multi-messenger astronomy. The frequency band of gravitational waves generated by various astronomical events can cover broadband range, and it is various for detection mechanism and scheme of gravitational waves in different frequency band. For example, The ground-based gravitational wave detection has the frequency band for 10 Hz to 10 kHz to mainly detect which based on Michelson interferometer; The space gravitational wave detection has the frequency band of 0.1 mHz to 1 Hz to mainly detect which based on space interferometer; The pulsar gravitational wave detection has the frequency band for 1×10<sup>-9</sup> Hz to 1×10<sup>-7</sup>Hz to mainly detect which based on pulsar timing array. The next generation ground-based gravitational wave project demands higher sensitivity to detect faint signals, necessitating an assessment system with minimal background noise to accurately measure the laser relative intensity noise. At present, the detection frequency band of ground-based gravitational wave detection devices in operation is mainly concentrated in the range of 10 Hz - 10 kHz. To satisfying the detection sensitivity requirements, the laser relative intensity noise should be accurately evaluated and suppressed to ≤2.0×10<sup>-9</sup>Hz<sup>-1/2</sup>@10 Hz and ≤4.0×10<sup>-7</sup>Hz<sup>-1/2</sup>@10 kHz by photoelectric feedback. This paper constructed an evaluation and characterization system for ground-based gravitational wave band laser intensity noise which based on low noise and high sensitivity photoelectric detection device and combined with LabVIEW and MATLAB algorithm programming for instrument control and data processing. This low noise evaluation system is used to test the background noise of FFT analyzer SR760, preamplifier SR560, photoelectric detector electronics noise and intensity noise of self-developed optical fiber amplifier, and then the data extraction and image processing are carried out by LabVIEW and MATLAB algorithms, and finally the evaluation of ground-based gravitational wave frequency band system is obtained. The experimental results show that the whole electronic noise for the preamplifier SR560 and FFT analyzer SR760 is lower than 3.8×10<sup>-9</sup> Hz<sup>-1/2</sup>@(10 Hz-10 kHz). The electronic noise for the photodetector is lower than 1.4×10<sup>-8</sup>V/√Hz@10 Hz&8.1×10<sup>-9</sup>V/√Hz@10 kHz and the accuracy of the system is calibrated and tested by the standard sinusoidal signal. Finally, the noise of commercial laser is evaluated and compared with the factory data to verify the accuracy of the evaluation system. Related research, device and system development provide hardware, software and theoretical basis for the preparation of high-power low-noise laser light source and gravitational wave detection and provide theoretical basis and evaluation criteria for ground-based gravitational wave detection in China.

Primordial black holes in SB SUSY Gauss-Bonnet inflation

Here, we explore the formation of primordial black holes (PBHs) within a scalar field inflationary model coupled to the Gauss-Bonnet (GB) term, incorporating the low-scale spontaneously broken supersymmetric (SB SUSY) potential.The coupling function amplifies the curvature perturbations, consequently leading to the formation of PBHs and detectable secondary gravitational waves (GWs).Through the adjustment of the model parameters, the inflaton can be decelerated during an ultra-slow-roll (USR) phase, thereby augmenting curvature perturbations. Beside the observational constraints, the swampland criteria are investigated.Our computations forecast the formation of PBHs with masses around 𝒪(10)M ⊙, aligning with the observational data of LIGO-Virgo, and PBHs with masses 𝒪(10-6)M ⊙ as potential explanation for the ultrashort-timescale microlensing events recorded in the OGLE data.Additionally, our proposed mechanism can generate PBHs with masses around 𝒪(10-13)M ⊙, constituting roughly 99% of the dark matter.The density parameters of the produced GWs (ΩGW 0) intersect with the sensitivity curves of GW detectors. Two cases of our model fall within the nano-Hz frequency regime. One of them satisfies the power-law scaling as ΩGW(f) ∼ f 5-γ, with the γ = 3.51, which is consistent with the data of NANOGrav 15-year.

Gravitational waveforms from periodic orbits around a quantum-corrected black hole

Extreme mass-ratio inspirals are crucial sources for future space-based gravitational wave detections. Gravitational waveforms emitted by extreme mass-ratio inspirals are closely related to the orbital dynamics of small celestial objects, which vary with the underlying spacetime geometry. Despite the tremendous success of general relativity, there are unsolved issues such as singularities in both black holes and cosmology. Loop quantum gravity, a theory addressing these singularity problems, offers a framework for regular black holes. In this paper, we focus on periodic orbits of a small celestial object around a supermassive quantum-corrected black hole in loop quantum gravity and compute the corresponding gravitational waveforms. We view the small celestial object as a massive test particle and obtain its four-velocity and effective potential. We explore the effects of quantum corrections on marginally bound orbits, innermost stable circular orbits, and other periodic orbits. Using the numerical kludge scheme, we further explore the gravitational waveforms of the small celestial object along different periodic orbits. The waveforms exhibit distinct zoom and whirl phases in a complete orbital period, closely tied to the quantum parameter α̂. We also perform a spectral analysis of the gravitational waves from these periodic orbits and assess their detectability. With the steady progress of space-based gravitational wave detection programs, our findings will contribute to utilizing extreme mass-ratio inspirals to test and understand the properties of quantum-corrected black holes.

Merging Black Holes: Insights from Gravitational Wave Observations

Before the first formal and direct detection of gravitational waves happened in 2015 by LIGO, Einstein had already predicted its presence in 1916 through his theory of general relativity. These gravitational waves are produced in cosmic events such as colliding and merging black holes, which means that their detection and investigation can be used to study the characteristics and properties of Black Hole Mergers. Studying black hole mergers can enable us to gain a deeper understanding of the universe’s cosmic history and structure. This paper provides a brief summary on the insights of Black Hole mergers from Gravitational Wave Observations, while also exploring some of the observational technique used, such as the technique of interferometry and Pulsar Timing arrays.

Analysis of laser spot centroiding errors for laser acquisition system in gravitational wave detection missions.

In space-based gravitational wave detection, establishing ultra-long-distance and ultra-high-precision laser links between satellites is achieved through the laser acquisition and tracking system. The laser spot centroid positioning method, which offers low computational complexity and strong adaptability to beam shape, is currently the core measurement method during the laser acquisition phase. However, due to various interference factors encountered in practical tests, this algorithm often falls short of meeting the extremely high requirements. To address this challenge, this paper first defines the specific performance criteria for the centroid positioning method based on the needs of laser acquisition in gravitational wave detection. It then comprehensively analyzes how detector noise, window truncation effects, and beam wavefront aberrations impact the accuracy of angular measurements. Using derived analytical expressions, an improved centroiding algorithm is proposed to mitigate the effects of detector noise and wavefront aberrations simultaneously. Numerical simulations are conducted to design the specific parameters for the algorithm and the system, resulting in the ability to achieve an angular measurement accuracy of 60 nrad at the telescope front end.

Constraining the Binarity of Massive Black Holes in the Galactic Center and Some Nearby Galaxies via Pulsar Timing Array Observations of Gravitational Waves

Massive black holes (MBHs) exist in the Galactic center (GC) and other nearby galactic nuclei. As a natural outcome of galaxy mergers, some MBHs may have a black hole (BH) companion. In this paper, assuming that the MBHs in the GC and some nearby galaxies are in binaries with orbital periods ranging from months to years (gravitational-wave frequency ∼1–100 nHz), we investigate the detectability of gravitational waves from these binary MBHs (BBHs) and constraints on the parameter space for the existence of BBHs in the GC, Large Magellanic Cloud (LMC), M31, M32, and M87 that may be obtained by current/future pulsar timing array (PTA) observations. We find that a BBH in the GC, if any, can be revealed by the Square Kilometre Array PTA (SKA-PTA) if it has mass ratio q ≳ 10−4–10−3 and semimajor axis a ∼ 20–103 au. The existence of a BH companion of the MBH can be revealed by SKA-PTA with ∼20 yr observations in M31 if q ≳ 10−4 and a ∼ 102–104 au or in M87 if q ≳ 10−5 and a ∼ 103–2 × 104 au, but not in the LMC and M32 if q ≪ 1. If a number of millisecond stable pulsars with distances ≲0.1–1 pc away from the central MBH in the GC, the LMC, M32, or M31 can be detected in future and applied to PTAs, a BH companion with mass even down to ∼100 M ⊙, close to stellar masses, can be revealed by such PTAs. Future PTAs are expected to provide an independent way to reveal BBHs and low-mass MBH companions in the GC and nearby galaxies, improving our understandings of the formation and evolution of MBHs and galaxies.

Design and test of the electrostatic actuation system of the inertial sensor for space gravitational wave detection

Design and test of the electrostatic actuation system of the inertial sensor for space gravitational wave detection

Large-scale dual AGN in large-scale cosmological hydrodynamical simulations

Abstract Detecting dual active galactic nuclei (DAGN) in observations and understanding theoretically which massive black holes (MBHs) compose them and in which galactic and large-scale environment they reside are becoming increasingly important questions as we enter the multi-messenger era of MBH astronomy. This paper presents the abundance and properties of DAGN produced in nine large-scale cosmological hydrodynamical simulations. We focus on DAGN powered by AGN with $L_{\rm bol}\geqslant 10^{43}\, \rm erg\, s^{-1}$ and belonging to distinct galaxies, i.e. pairs that can be characterised with current and near-future electromagnetic observations. We find that the number density of DAGN separated by a few to 30 proper kpc varies from 10−8 (or none) to $10^{-3} \, \rm comoving\, Mpc^{3}$ in the redshift range z = 0–7. At a given redshift, the densities of the DAGN numbers vary by up to two orders of magnitude from one simulation to another. However, for all simulations, the DAGN peak is in the range z = 1–3, right before the peak of cosmic star formation or cosmic AGN activity. The corresponding fractions of DAGN (with respect to the total number of AGN) range from 0 to 6 %. We find that simulations could produce too few DAGN at z = 0 (or merge pairs too quickly) compared to current observational constraints while being consistent with preliminary constraints at high redshift (z ∼ 3). Next-generation observatories (e.g., AXIS) will be of paramount importance to detect DAGN across cosmic times. We predict the detectability of DAGN with future X-ray telescopes and discuss DAGN as progenitors for future LISA gravitational wave detections.