arXiv subjects

Yi-Fan Wang

Publications and source records attributed to Yi-Fan Wang.

At least 19 recordsLinked to original sources

arXiv2026

Testing Source Dependence in Gravitational-Wave Tests of General Relativity with Mutual Information

Phenomenological deviation parameters used in gravitational-wave tests of general relativity need not represent universal fundamental properties of the sources. Instead, a deviation parameter can be a derived quantity that depends on source properties. Apparent violations of general relativity arising from waveform systematics or data-quality issues can also depend on source properties. In addition to diagnosing individual events, it is helpful to identify systematic trends at the population level. We introduce a nonparametric framework that uses mutual information to test whether the deviations depend on source properties. We validate the framework using simulations with massive graviton waveforms. Assuming we do not have prior knowledge of the underlying theory, massive graviton effects can be captured by a parameterized post-Einstein coefficient that is expected to depend on the luminosity distance and source mass. The results show that the mass and distance dependencies become clear for graviton masses of $\geq 1\times10^{-22}\,\mathrm{eV}$ at detector sensitivities representative of the current fourth observing run, while the controlled general relativity simulations yield null results. We then analyze public real-data products for tests of general relativity from GWTC-4.0 and 4-OGC, including phenomenological parameterized tests, modified dispersion tests, and parity violation tests. The phenomenological deviation parameters have tentative correlations with effective spin, and correlations of modified-dispersion or parity-violation parameters with source mass are visible. These results demonstrate that catalog-level dependence can identify patterns and thus be used to diagnose the origin of deviations in testing general relativity. The framework therefore complements single-event analyses and parameterized hierarchical population tests.

gr-qc↗

arXiv2026

Robust Deepfake Detection, NTIRE 2026 Challenge: Report

Robustness is a long-overlooked problem in deepfake detection. However, detection performance is nearly worthless in the real world if it suffers under exposure to even slight image degradation. In addition to weaker degradations that can accidentally occur in the image processing pipeline, there is another risk of malicious deepfakes that specifically introduce degradations, purposefully exploiting the detector's weaknesses in that regard. Here, we present an overview of the NTIRE 2026 Robust Deepfake Detection Challenge, which specifically addresses that problem. Participants were tasked with building a detector that would later be tested on an unknown test-set, which included both common and uncommon degradations of various strengths. With a total number of 337 participants and 57 submissions to the final leaderboard, the first edition of the challenge was well received. To ensure the reliability of the results, participants were given only 24h to complete the test run with no labels provided, limiting the possibility of training on the test data. Furthermore, the top solutions were scored on a private test-set to detect any such overfitting. This report presents the competition setting, dataset preparation, as well as details and performance of methods. Top methods rely on large foundation models, ensembles, and degradation training to combine generality and robustness.

cs.CV↗

arXiv2026

A nonlinear voice from GW250114 ringdown

The detection of quadratic quasi-normal modes would provide a direct probe into black hole nonlinear perturbations. We report the first observational evidence of a set of quadratic quasi-normal modes in the gravitational-wave ringdown of a binary black hole merger. Analyzing the signal from GW250114, we detect six nonlinear modes from the quadratic coupling of the fundamental $(2,2,0)$ mode and its first two overtones. At 5 final mass ($M_\mathrm{f}$) after the merger, the evidence for these nonlinear modes reaches a Bayes factor of 74. To single out these contributions, we employ recent theoretical progress to compute the waveforms and subtract the corresponding nonlinear modes from a numerical relativity surrogate waveform. Our data analysis uses a novel method that incorporates inspiral-merger inference results as a highly constraining prior for the ringdown inference. We further perform a test allowing for phenomenological deviations for the theoretically predicted amplitudes of the quadratic modes. The results show that an amplitude of zero is excluded at $3.0~\sigma$ significance level, while the theoretical expectation is consistent with the inference. This detection marks a first step towards observationally characterizing nonlinear perturbations in the ringdown of a black hole.

gr-qc↗

arXiv2025

Photometric and Spectroscopic Studies of Four Low Mass-ratio Contact Binaries with Period Longer than 0.7 days

Photometric and spectroscopic studies of four long-period low mass-ratio contact binaries, V0508 And, V0844 Aur, V0699 Cep, and NSVS 6259046, are performed. V0508 And, V0844 Aur, and V0699 Cep are found to be A-type low-mass-ratio medium-contact binaries, while NSVS 6259046 is found to be an A-type deep-contact binary. O - C analysis indicates no long-term variation in V0844 Aur. However, the orbital periods of the other three targets are increasing. We conclude that V0844 Aur, V0699 Cep and NSVS 6259046 are magnetically active, as evidenced by the presence and variable nature of the O'Connell effect in these systems. By analyzing the LAMOST spectroscopic data, we find out that NSVS 6259046 and V0508 And exhibit no chromospheric activity on the dates the LAMOST spectra were taken, while the low signal-to-noise ratio in LAMOST data for V0844 Aur prevents us from obtaining reliable results. We discover that V0699 Cep is an early-type contact binary with chromospheric activity. Their initial masses and ages are calculated. All four systems are determined to be currently stable. We collect 217 contact binaries with both spectroscopic and photometric observations, and compare the differences between short-period and long-period systems in terms of mass-luminosity relation and mass-radius relation, using 0.7 days as the period boundary.

astro-ph.SR↗

arXiv2025

Search for gravitational waves from eccentric binary black holes with an effective-one-body template

As gravitational wave astronomy has entered an era of routine detections, it becomes increasingly important to precisely measure the physical parameters of individual events and infer population properties. Eccentricity is a key observable, suggesting that binaries form in a dense stellar environment through dynamical encounters. This work performs the first matched-filtering search for gravitational waves from eccentric binary black holes (BBHs) covering the mass range $[5, 200]~M_\odot$ and eccentricity at 20 Hz up to 0.5 with a newly developed effective-one-body waveform model. Throughout the third observation run of LIGO, Virgo, and KAGRA, we identify 28 BBH events with a false alarm rate below once per 100 yr; all of which were previously reported in the GWTC-3 and 4-OGC catalogs. Additional candidates with false alarm rates between once per 1 and 100 yr are also reported. We perform an injection campaign to characterize the sensitive volume time of our search pipeline. Assuming that none of the eccentric BBH events were missed by previous searches, our results provide constraints on the event rate of eccentric BBHs in the mass range [5, 30] $M_\odot$. For a 30-30 $M_\odot$ BBH with eccentricity 0.5, the event rate is limited to less than 0.06 Gpc$^{-3}$ yr$^{-1}$; this marks an order of magnitude improvement for sensitive volume compared with the previous search with a minimally modeled algorithm without using templates.

gr-qc↗

arXiv2025

A gating-and-inpainting perspective on GW150914 ringdown overtone: understanding the data analysis systematics

We revisit the recent debate on the evidence for an overtone in the black hole ringdown of GW150914 using an independent data-analysis pipeline. By gating and inpainting the data, we discard the contamination from earlier parts of the gravitational wave signal before ringdown. This enables parameter estimation to be conducted in the frequency domain, which is mathematically equivalent to the time domain method. We keep the settings as similar as possible to the previous studies by Cotesta et al. arXiv:2201.00822 and Isi et al. arXiv:1905.00869 arXiv:2202.02941 which yielded conflicting results on the Bayes factor of the overtone. Our aim is to understand how different data analysis systematics, including sampling rates, erroneous timestamps, and the frequency resolution of the noise power spectrum, would influence the statistical significance of an overtone. Our main results indicate the following: (i) a low-resolution estimation of the noise power spectrum tends to diminish the significance of overtones, (ii) adjusting the start time to a later digitized point reduces the significance of overtones, and (iii) overtone evidence varies with different sampling rates if the start time is too early, indicating that the overtone is a poor model, hence we propose a convergence test to verify the validity of an overtone model. With these issues addressed, we find the Bayes factors for the overtone to range from $10$ to $26$ in a range of times centered at the best-fit merger time of GW150914, which supports the existence of an overtone in agreement with the conclusions of Isi et al. arXiv:1905.00869 arXiv:2202.02941. These results are obtained by keeping the start time and sky location fixed, enabling a direct comparison with other work. Marginalizing over these parameters would lower the Bayes factor to 1 for the evidence of an overtone.

gr-qc↗

arXiv2025

Extremely Low Mass Ratio Contact Binaries. II. The First Photometric and Spectroscopic Investigations of Six Systems with Orbital Periods Longer than 0.5 days

The photometric and spectroscopic studies of six contact binaries were performed for the first time. The orbital periods of all the six targets are longer than 0.5d, and we discovered that their mass ratios are smaller than 0.15. So, they are extremely low mass-ratio contact binaries. Only one target is a W-subtype contact binary (ASASSN-V J105032.88+420829.0), while the others are A-subtype contact binaries. From orbital period analysis, ASASSN-V J075442.44+555623.2 shows no orbital period change. Three of the six targets demonstrate a secular period increase, and two targets for a secular period decrease. We investigated the LAMOST spectra employing the spectral subtraction method. All six contact binaries show no chromospheric emission line, implying no chromospheric activity. Their absolute parameters, initial masses, ages, energy transfer parameters, and instability parameters were calculated. The bolometric luminosity ratios ($(L_2/L_1)_{bol}$), the energy transfer parameters ($β$), the contact degrees ($f$), and the mass ratios ($q$) were collected for a sample of 218 contact binaries and we analyzed and discussed some correlations. The results by analyzing the relation between $β$, $f$ and $q$ indicate that the energy transfer parameter between the two components of extremely low mass-ratio contact binaries is independent of the contact degree. And the predicted cutoff mass ratio was estimated as 0.021 by analyzing the relation between $f$ and $q$.

astro-ph.SR↗

arXiv2025

Public Opinion and The Rise of Digital Minds: Perceived Risk, Trust, and Regulation Support

Governance institutions must respond to societal risks, including those posed by generative AI. This study empirically examines how public trust in institutions and AI technologies, along with perceived risks, shape preferences for AI regulation. Using the nationally representative 2023 Artificial Intelligence, Morality, and Sentience (AIMS) survey, we assess trust in government, AI companies, and AI technologies, as well as public support for regulatory measures such as slowing AI development or outright bans on advanced AI. Our findings reveal broad public support for AI regulation, with risk perception playing a significant role in shaping policy preferences. Individuals with higher trust in government favor regulation, while those with greater trust in AI companies and AI technologies are less inclined to support restrictions. Trust in government and perceived risks significantly predict preferences for both soft (e.g., slowing development) and strong (e.g., banning AI systems) regulatory interventions. These results highlight the importance of public opinion in AI governance. As AI capabilities advance, effective regulation will require balancing public concerns about risks with trust in institutions. This study provides a foundational empirical baseline for policymakers navigating AI governance and underscores the need for further research into public trust, risk perception, and regulatory strategies in the evolving AI landscape.

cs.CY↗

arXiv2024

The first exploration of the correlations between \textit{WISE} 12 \micron\ and CO emission in early-type galaxies

We present the analysis of a comprehensive sample of 352 early-type galaxies using public data, to investigate the correlations between CO luminosities and mid-infrared luminosities observed by \textit{Wide-field Infrared Survey Explorer} (\textit{WISE}). We find strong correlations between both CO (1-0) and CO (2-1) luminosities and 12 \micron\ luminosity, boasting a correlation coefficient greater than 0.9 and an intrinsic scatter smaller than 0.1 dex. The consistent slopes observed for the relationships of CO (1-0) and CO (2-1) suggest that the line ratio R21 lacks correlation with mid-infrared emission in early-type galaxies, which is significantly different from star-forming galaxies. Moreover, the slopes of $L_{\rm CO (1-0)}$--$L_{\mbox{12\micron}}$ and $L_{\rm CO (2-1)}$--$L_{\mbox{12\micron}}$ relations in early-type galaxies are steeper than those observed in star-forming galaxies. Given the absence of correlation with color, morphology or sSFR, the correlation between deviations and the molecular gas mass surface density could be eliminated by correcting the possible 12 \micron\ emission from old stars or adopting a systematically different $α_{\rm CO}$. The latter, on average, is equivalent to adding an constant CO brightness density, specifically ${2.8{_{-0.6}}\!\!\!\!\!\!\!\!\!^{+0.8}}~[\mathrm{K~km~s^{-1}}]$ and ${4.4{_{-1.4}}\!\!\!\!\!\!\!\!\!^{+2.2}}~[\mathrm{K~km~s^{-1}}]$ for CO (1-0) and (2-1) respectively. These explorations will serve as useful tools for estimating the molecular gas content in gas-poor galaxies and understanding associated quenching processes.

astro-ph.GA↗

arXiv2024

Photometric and Spectroscopic Investigations of Three Large Amplitude Contact Binaries

We performed photometric and spectroscopic studies of three large amplitude contact binaries, NSVS 2418361, ATLAS J057.1170+31.2384 and NSVS 7377875. The amplitudes of three systems' light curves are more than 0.7 magnitude. We analyzed the light curves using Wilson-Devinney code to yield physical parameters. The photometric solutions suggested that NSVS 7377875 belongs to an A-subtype contact binary, while the others are classified as W-subtype ones. Furthermore, the mass ratio of NSVS 7377875 is higher than 0.72, so it belongs to H-subtype contact binaries. Since their light curves have unequal height at two maxima which is called O'Connell effect, a dark spot on the primary component for each target was required to get a better fit of light curves. The orbital period investigation shows that the period of NSVS 2418361 is increasing, indicating a mass transfer from the less massive component to the more massive one, while the other targets exhibit no long-term variation. Our spectral subtraction analysis of LAMOST spectra revealed excess emissions in the $H_α$ line, indicating chromospheric activity in all the three targets. The Gaia distance was applied to estimate the absolute parameters of the three targets, and we obtained their evolutionary state. The relationships between the energy transfer parameter of 76 H-subtype contact binaries and their bolometric luminosity ratios, as well as their contact degree, were presented. We discovered that H-subtype systems have less efficient energy transfer rate, which is corresponding to the conclusion proposed by Csizmadia \& Klagyivik.

astro-ph.SR↗

arXiv2024

Estimating False Alarm Rates of Sub-Dominant Quasi-normal Modes in GW190521

A major aim of gravitational wave astronomy is to test observationally the Kerr nature of black holes. The strongest such test, with minimal additional assumptions, is provided by observations of multiple ringdown modes, also known as black hole spectroscopy. For the gravitational wave merger event GW190521, we have previously claimed the detection of two ringdown modes emitted by the remnant black hole. In this paper we provide further evidence for the detection of multiple ringdown modes from this event. We analyse the recovery of simulated gravitational wave signals designed to replicate the ringdown properties of GW190521. We quantify how often our detection statistic reports strong evidence for a sub-dominant $(\ell,m,n)=(3,3,0)$ ringdown mode, even when no such mode is present in the simulated signal. We find this only occurs with a probability $\sim 0.02$, which is consistent with a Bayes factor of $t_{\rm ref} + 6\,\mathrm{ms}$ (1$σ$ uncertainty) found for GW190521. We also quantify our agnostic analysis of GW190521, in which no relationship is assumed between ringdown modes, and find that only 1 in 250 simulated signals without a $(3,3,0)$ mode yields a result as significant as GW190521. Conversely, we verify that when simulated signals do have an observable $(3,3,0)$ mode they consistently yield a strong evidence and significant agnostic results. We also find that constraints on deviations from the $(3,3,0)$ mode on GW190521-like signals with a $(3,3,0)$ mode are consistent with what was obtained from our previous analysis of GW190521. Our results support our previous conclusion that the gravitational wave signal from GW190521 contains an observable sub-dominant $(\ell,m,n)=(3,3,0)$ mode.

gr-qc↗

arXiv2024

Low evidence for ringdown overtone in GW150914 when marginalizing over time and sky location uncertainty

Tests of the no-hair theorem using astrophysical black holes involve the detection of at least two quasi-normal modes (QNMs) in the gravitational wave emitted by a perturbed black hole. A detection of two modes -- the dominant, $(\ell, m, n) = (2,2,0)$, mode and its first overtone, the $(2,2,1)$ mode -- in the post-merger signal of the binary black hole merger GW150914 was claimed in Isi et al. [arXiv:1905.00869], with further evidence provided in Isi & Farr [arXiv:2202.02941]. However, Cotesta et al. [arXiv:2201.00822] disputed this claim, finding that evidence for the overtone only appeared if the signal was analyzed before merger, when a QNM description of the signal is not valid. Due to technical challenges, both of these analyses fixed the merger time and sky location of GW150914 when estimating the evidence for the overtone. At least some of the contention can be attributed to fixing these parameters. Here, we surmount this difficulty and fully marginalize over merger time and sky-location uncertainty while doing a post-merger QNM analysis of GW150914. We find that marginalizing over all parameters yields low evidence for the presence of the overtone, with a Bayes factor of $1.10\pm 0.03$ in favor of a QNM model with the overtone versus one without. The arrival time uncertainty of GW150914 is too large to definitively claim detection of the $(2,2,1)$ mode.

gr-qc↗

arXiv2024

Measurement of three-body recombination coefficient of ultracold lithium and strontium atoms

We report on the observation of a conspicuous loss in an ultracold mixture of $^{7}$Li and $^{88}$Sr atoms confined in a far-off-resonance optical dipole trap. We attribute the trap loss to the three-body inelastic Li-Sr-Sr collision and extract the corresponding three-body recombination coefficient $K_3$ at $T\sim 18.5,45,70,600$ $μK$. The measured three-body recombination coefficient is about two to three orders of magnitude larger than the typical values convenient for realizing quantum degenerate gases. It also indicates a potentially large $s$-wave scattering length between the bosonic $^{7}$Li and $^{88}$Sr atoms, and essentially rules out the prospect of realizing $^7$Li and $^{88}$Sr mixtures of high phase space density.

physics.atom-ph↗

arXiv2024

Targeted Search for Gravitational Waves from Highly Spinning Light Compact Binaries

Searches for gravitational waves from compact-binary mergers, which to date have reported $\sim100$ observations, have previously ignored binaries whose components are both consistent with the mass of neutron stars $(1 M_\odot$ to $ 2 M_\odot)$ and have high dimensionless spin $>0.05$. While previous searches targeted sources that are representative of observed neutron star binaries in the galaxy, it is already known that neutron stars can regularly be spun up to a dimensionless spin of $\sim0.4$, and in principle reach up to $\sim0.7$ before breakup would occur. Furthermore, there may be primordial black hole binaries or exotic formation mechanisms to produce light black holes. In these cases, it is possible for the binary constituent to be spun up beyond that achievable by a neutron star. A single detection of this type of source would reveal a novel formation channel for compact-binaries. To determine if there is evidence for any such sources, we use PyCBC to conduct a targeted search of LIGO and Virgo data for light compact objects with high spin. Our analysis detects previously known observations GW170817 and GW200115; however, we report no additional mergers. The most significant candidate, not previously known, is consistent with the noise distribution, and so we constrain the merger rate of spinning light binaries.

astro-ph.HE↗

arXiv2023

Spectroscopy for asymmetric binary black hole mergers

We study Bayesian inference of black hole ringdown modes for simulated binary black hole signals. We consider to what extent different fundamental ringdown modes can be identified in the context of black hole spectroscopy. Our simulated signals are inspired by the high mass event GW190521. We find strong correlation between mass ratio and Bayes factors of the subdominant ringdown modes. The Bayes factor values and time dependency, and the peak time of the (3,3,0) mode align with those found analyzing the real event GW190521, particularly for high-mass ratio systems.

gr-qc↗

arXiv2023

A multimode quasi-normal spectrum from a perturbed black hole

When two black holes merge, the late stage of gravitational wave emission is a superposition of exponentially damped sinusoids. According to the black hole no-hair theorem, this ringdown spectrum depends only on the mass and angular momentum of the final black hole. An observation of more than one ringdown mode can test this fundamental prediction of general relativity. Here we provide strong observational evidence for a multimode black hole ringdown spectrum using the gravitational wave event GW190521, with a maximum Bayes factor of $56\pm1$ ($1σ$ uncertainty) preferring two fundamental modes over one. The dominant mode is the $\ell=m=2$ harmonic, and the sub-dominant mode corresponds to the $\ell=m=3$ harmonic. The amplitude of this mode relative to the dominant harmonic is estimated to be $A_{330}/A_{220} = 0.2^{+0.2}_{-0.1}$. We estimate the redshifted mass and dimensionless spin of the final black hole as $330_{-40}^{+30}~\mathrm{M}_{\odot}$ and $0.86_{-0.11}^{+0.06}$, respectively. We find that the final black hole is consistent with the no hair theorem and constrain the fractional deviation from general relativity of the sub-dominant mode's frequency to be $-0.01^{+0.08}_{-0.09}$.

gr-qc↗

arXiv2022

Singularities of regular black holes and the monodromy method for asymptotic quasinormal modes

We use the monodromy method to investigate the asymptotic quasinormal modes of regular black holes based on the explicit Stokes portraits. We find that, for regular black holes with spherical symmetry and a single shape function, the analytical forms of the asymptotic frequency spectrum are not universal and do not depend on the multipole number but on the presence of complex singularities and the trajectory of asymptotic solutions along the Stokes lines.

gr-qc↗

arXiv2022

Tests of Gravitational-Wave Birefringence with the Open Gravitational-Wave Catalog

We report the results of testing gravitational-wave birefringence using the largest population of gravitational-wave events currently available. Gravitational-wave birefringence, which can arise from the effective field theory extension of general relativity, occurs when the parity symmetry is broken, causing the left- and right-handed polarizations to propagate following different equations of motion. We perform Bayesian inference on the 94 events reported by the 4th-Open Gravitational-wave Catalog (4-OGC) using a parity-violating waveform. We find no evidence for a violation of general relativity in the vast majority of events. However, the most massive event, GW190521, and the second most massive event, GW191109, show intriguing non-zero results for gravitational-wave birefringence. We find that the probability of association between GW190521 and the possible electromagnetic (EM) counterpart reported by Zwicky Transient Facility (ZTF) is increased when assuming birefringence. Excluding GW190521 and GW191109, the parity-violating energy scale is constrained to $M_\mathrm{PV} > 0.05$ GeV at $90\%$ credible interval, which is an improvement over previous results from twelve events by a factor of five. We discuss the implications of our results on modified gravity and possible alternative explanations such as waveform systematics. More detections of massive binary black hole mergers from the upcoming LIGO/Virgo/KAGRA run will shed light on the true origin of the apparent birefringence.

astro-ph.HE↗