Detection Of Gravitational Waves Research Articles

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.

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.

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.

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.

Gravitational wave signatures of first-order phase transition in two-component dark matter model

Here, we consider a classically scale-invariant extension of the Standard Model (SM) with two-component dark matter (DM) candidates, including a Dirac spinor and a scalar DM. We probe the parameter space of the model, constrained by relic density and direct detection, and investigate the generation of gravitational waves (GWs) produced by an electroweak first-order phase transition. The analysis demonstrates that there are points in the parameter space, leading to a detectable GW spectrum arising from the first-order phase transition, which is also consistent with the DM relic abundance and direct detection bounds. These GWs could be observed by forthcoming space-based interferometers such as the Big Bang Observer, Decihertz Interferometer Gravitational-wave Observatory, and Ultimate-Decihertz Interferometer Gravitational-wave Observatory. Published by the American Physical Society 2024

Gravitational Wave Detectors—Past, Present, and Future

Since the beginning of my career, I have been fascinated by the phenomenon of gravitational waves—ripples in space and time that spread at the speed of light. At first, my interest was simply in understanding the concepts, but once I realized there was a possibility to actually detect gravitational waves, I was hooked. I decided to join the efforts to design and build gravitational wave detectors, and I worked on that challenge for a few decades until the first successful detection in 2015. In this article, I will tell you about how a gravitational wave detection instrument called LIGO came about, how my students and I helped improve it, and what the future holds for LIGO and for other gravitational wave detectors that could revolutionize our understanding of the universe.

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

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

Building a Semi-analytic Black Hole Seeding Model using IllustrisTNG Host Galaxies

ABSTRACT A major open question in astrophysics is the mechanisms by which massive black holes (BHs) form in the early Universe, which pose constraints on seeding models. We study BH formation and evolution in a flexible model combining the cosmological IllustrisTNG (TNG) simulations with semi-analytic modelling in post-processing. We identify our TNG model hosts based on various criteria including a minimum gas mass of $10^7$–$10^9$${\rm M}_{\odot }$, total host mass of $10^{8.5}$–$10^{10.5}$${\rm M}_{\odot }$, and a maximum gas metallicity of 0.01–0.1 $\mathrm{Z}_{\odot }$. Each potential host is assigned a BH seed with a probability of 0.01–1. The populations follow the TNG galaxy merger tree. This approach improves upon the predictive power of the simple TNG BH seeding prescription, narrowing down plausible seeding parameter spaces, and it is readily adaptable to other cosmological simulations. Several model realizations predict $z\lesssim 4$ BH mass densities that are consistent with empirical data as well as the TNG BHs. However, high-redshift BH number densities can differ by factors of $\sim$ 10 to $\gtrsim$ 100 between seeding parameters. In most model realizations, $\lesssim 10^5$${\rm M}_{\odot }$ BHs substantially outnumber heavier BHs at high redshifts. Mergers between such BHs are prime targets for gravitational-wave detection with Laser Interferometer Space Antenna. The $z=0$ BH mass densities in most realizations of the model agree well with observations, but our strictest seeding criteria fail at high redshift. Our findings strongly motivate the need for better empirical constraints on high-z BHs, and they underscore the significance of recent active galactic nucleus discoveries with JWST.

Optimal input excitations for suppressing nonlinear instabilities in multimode fibers

Wavefront shaping has become a powerful tool for manipulating light propagation in various complex media undergoing linear scattering. Controlling nonlinear optical interactions with spatial degrees of freedom is a relatively recent but fast growing area of research. A wavefront-shaping-based approach can be used to suppress nonlinear stimulated Brillouin scattering (SBS) and transverse mode instability (TMI), which are the two main limitations to power scaling in high-power narrowband fiber amplifiers. Here we formulate both SBS and TMI suppression as optimization problems with respect to coherent multimode input excitation in a given multimode fiber. We develop an efficient method using linear programming for finding the globally optimal input excitation for minimizing SBS and TMI individually or jointly. The theory shows that optimally exciting a standard multimode fiber leads to roughly an order of magnitude enhancement in instability-free output power compared to fundamental-mode-only excitation. We find that the optimal mode content is robust to small perturbations and our approach works even in the presence of mode-dependent loss and gain. When such optimal mode content is excited in real experiments using spatial light modulators, the stable range of ultrahigh-power fiber lasers can be substantially increased, enabling applications in gravitation wave detection, advanced manufacturing, and defense.

Researching the detection of continuous gravitational waves based on signal processing and ensemble learning

Researching the detection of continuous gravitational waves based on signal processing and ensemble learning

Amplitude stability research and experimental investigation of the actuation circuit of the inertial sensor for space gravitational wave detection

Abstract The primary measure of scientific performance for inertial sensors used in space gravitational wave detection is the residual acceleration noise of the test mass (TM). This residual noise arises from both the internal circuit and the external environment. The actuation circuit, a crucial component of the internal circuit, significantly affects the TM’s residual acceleration noise through its amplitude stability, thereby impacting the scientific performance of the inertial sensor. In this study, we designed the actuation circuit for an inertial sensor, developed a mathematical model to describe its amplitude stability, and experimentally verified the model's accuracy. Experimental results demonstrate that the current design enables the actuation circuit to achieve an amplitude stability of 3.6 ppm/Hz1/2 at 1 mHz, thereby offering theoretical support for achieving a higher amplitude stability in the millihertz frequency band.

Torsion Pendulum Apparatus for Ground Testing of Space Inertial Sensor.

The precise movement of the test mass along a geodesic is crucial for gravitational wave detection in space. To maintain this motion, the core payload-inertial sensor incorporates multiple functional units designed to mitigate various sources of stray force noise affecting the test mass. Understanding the limits of these noise sources is essential for enhancing the inertial sensor system design. Additionally, thorough ground-based verification of these functional units is necessary to ensure their reliability for space missions. To address these challenges, we developed a low-frequency torsion pendulum apparatus that utilizes a commercial autocollimator as the optical readout element for testing this type of space inertial sensor. This paper provides a comprehensive overview of the apparatus's operating principle, structural characteristics, and the results of laboratory tests of its background noise. Experimental data demonstrate that the torsion pendulum achieves a sensitivity of 1 × 10-11 Nm/Hz1/2 within the measurement band from 1 mHz to 0.1 Hz, confirming its suitability for various inertial sensor tests. Furthermore, the insights gained from constructing the torsion pendulum will inform future system upgrades.

Primordial Black Holes and Gravitational Waves in the U(1)B−L extended inert doublet model: a first-order phase transition perspective

We conduct an analysis of a U(1)B−L extended inert doublet model and obtained the parameter space allowing strong first order phase transitions. We show that a large part of the parameter space can cause double first-order phase transitions. Whereas both of these phase transitions can generate a detectable stochastic gravitational wave background, one of them can create primordial black holes with appreciable abundance. The primordial black holes generated at the high scale transition can account for the dark matter maintaining the correct relic abundance. We also show specific benchmark cases and their consequences from the aspect of primordial black holes and gravitational waves.

The MeerKAT Pulsar Timing Array: the first search for gravitational waves with the MeerKAT radio telescope

ABSTRACT Pulsar timing arrays search for nanohertz-frequency gravitational waves by regularly observing ensembles of millisecond pulsars over many years to look for correlated timing residuals. Recently the first evidence for a stochastic gravitational wave background has been presented by the major arrays, with varying levels of significance (${\sim} 2\sigma \!-\! 4\sigma$). In this paper, we present the results of background searches with the MeerKAT Pulsar Timing Array. Although of limited duration (4.5 yr), the ${\sim} 250\,000$ arrival times with a median error of just $3 \, \mu {\rm s}$ on 83 pulsars make it very sensitive to spatial correlations. Detection of a gravitational wave background requires careful modelling of noise processes to ensure that any correlations represent a fit to the underlying background and not other misspecified processes. Under different assumptions about noise processes, we can produce either what appear to be compelling Hellings–Downs correlations of high significance ($3\sigma \!-\! 3.4\sigma$) with a spectrum close to that which is predicted, or surprisingly, under slightly different assumptions, ones that are insignificant. This appears to be related to the fact that many of the highest precision MeerKAT Pulsar Timing Array pulsars are in close proximity and dominate the detection statistics. The sky-averaged characteristic strain amplitude of the correlated signal in our most significant model is $h_{{\rm c}, {\rm yr}} = 7.5^{+0.8}_{-0.9} \times 10^{-15}$ measured at a spectral index of $\alpha =-0.26$, decreasing to $h_{{\rm c}, {\rm yr}} = 4.8^{+0.8}_{-0.9} \times 10^{-15}$ when assessed at the predicted $\alpha =-2/3$. These data will be valuable as the International Pulsar Timing Array project explores the significance of gravitational wave detections and their dependence on the assumed noise models.

Constraints on the primordial black hole abundance through scalar-induced gravitational waves from Advanced LIGO and Virgo's first three observing runs

As a promising dark matter candidate, primordial black holes (PBHs) lighter than ∼ 10-18 M ⊙ are supposed to have evaporated by today through Hawking radiation. This scenario is challenged by the memory burden effect, which suggests that the evaporation of black holes may slow down significantly after they have emitted about half of their initial mass. We explore the astrophysical implications of the memory burden effect on the PBH abundance by today and the possibility for PBHs lighter than ∼ 10-18 M ⊙ to persist as dark matter. Our analysis utilizes current LIGO-Virgo-KAGRA data to constrain the primordial power spectrum and infer the PBH abundance. We find a null detection of scalar-induced gravitational waves that accompanied the formation of the PBHs. Then we find that PBHs are ruled out within the mass range ∼ [10-24,10-19]M ⊙. Furthermore, we expect that next-generation gravitational wave detectors, such as the Einstein Telescope and the Cosmic Explorer, will provide even more stringent constraints. Our results indicate that future detectors can reach sensitivities that could rule out PBH as dark matter within ∼ [10-29 M ⊙,10-16 M ⊙] in the null detection of scalar-induced gravitational waves.