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Wen Zhao

Publications and source records attributed to Wen Zhao.

At least 109 records · Page 6Linked to original sources
arXiv2023

Labels Need Prompts Too: Mask Matching for Natural Language Understanding Tasks

Textual label names (descriptions) are typically semantically rich in many natural language understanding (NLU) tasks. In this paper, we incorporate the prompting methodology, which is widely used to enrich model input, into the label side for the first time. Specifically, we propose a Mask Matching method, which equips an input with a prompt and its label with another, and then makes predictions by matching their mask representations. We evaluate our method extensively on 8 NLU tasks with 14 datasets. The experimental results show that Mask Matching significantly outperforms its counterparts of fine-tuning and conventional prompt-tuning, setting up state-of-the-art performances in several datasets. Mask Matching is particularly good at handling NLU tasks with large label counts and informative label names. As pioneering efforts that investigate the label-side prompt, we also discuss open issues for future study.

cs.CL↗
arXiv2023

Measuring the Hubble constant with coalescences of binary neutron star and neutron star-black hole: bright sirens \& dark sirens

The observations of gravitational wave (GW) provide us a new probe to study the universe. GW events can be used as standard sirens if their redshifts are measured. Normally, stardard sirens can be divided into bright/dark sirens according to whether the redshifts are measured by electromagnetic (EM) counterpart observations. Firstly, we investigate the capability of the 2.5-meter Wide-Field Survey Telescope (WFST) to take follow-up observations of kilonova counterparts. For binary neutron star (BNS) bright sirens, WFST is expected to observe 10-20 kilonovae per year in the second-generation (2G) GW detection era. As for neutron star-black hole (NSBH) mergers, when a BH spin is extremely high and the NS is stiff, the observation rate is $\sim10$ per year. Combining optical and GW observations, the bright sirens are expected to constrain the Hubble constant $H_0$ to $\sim2.8\%$ in five years of observations. As for dark sirens, tidal effects of neutron stars (NSs) during merging time provide us a cosmological model-independent approach to measure the redshifts of GW sources. Then we investigate the applications of tidal effects in redshift measurements. We find in 3G era, the host galaxy groups of around 45\% BNS mergers at $z<0.1$ can be identified through this method, if the EOS is ms1, which is roughly equivalent to the results from luminosity distant constraints. Therefore, tidal effect observations provide a reliable and cosmological model-independent method of identifying BNS mergers' host galaxy groups. Using this method, the BNS/NSBH dark sirens can constrain $H_0$ to 0.2\%/0.3\% over a five-year observation period.

astro-ph.HE↗
arXiv2023

Constraints on the ghost-free parity-violating gravity from Laser-ranged Satellites

This paper explores the evolutionary behavior of the Earth-satellite binary system within the framework of the ghost-free parity-violating gravity and the corresponding discussion on the parity-violating effect from the laser-ranged satellites. For this purpose, we start our study with the Parameterized Post-Newtonian (PPN) metric of this gravity theory to study the orbital evolution of the satellites in which the spatial-time sector of the spacetime is modified due to the parity violation. With this modified PPN metric, we calculate the effects of the parity-violating sector of metrics on the time evolution of the orbital elements for an Earth-satellite binary system. We find that among the five orbital elements, the parity violation has no effect on the semi-latus rectum, while the eccentricity and ascending node are affected only in a periodic manner. These three orbital elements are the same as the results of general relativity and are also consistent with the observations of the present experiment. In particular, parity violation produces non-zero corrections to the eccentricity and pericenter, which will accumulate with the evolution of time, indicating that the parity violation of gravity produces observable secular effects. The observational constraint on the parity-violating effect is derived by confronting the theoretical prediction with the observation by the LAGEOS II pericenter advance, giving a constraint on the parity-violating parameter space from the satellite experiments.

gr-qc↗
arXiv2023

Synergy between CSST galaxy survey and gravitational-wave observation: Inferring the Hubble constant from dark standard sirens

Gravitational waves (GWs) from compact binary coalescences encode the absolute luminosity distances of GW sources. Once the redshifts of GW sources are known, one can use the distance-redshift relation to constrain cosmological parameters. One way to obtain the redshifts is to localize GW sources by GW observations and then use galaxy catalogs to determine redshifts from a statistical analysis of redshift information of the potential host galaxies, commonly referred to as the dark siren method. The third-generation (3G) GW detectors are planned to work in the 2030s and will observe numerous compact binary coalescences. Using these GW events as dark sirens requires high-quality galaxy catalogs from future sky survey projects. The China Space Station Telescope (CSST) will be launched in 2024 and will observe billions of galaxies within a 17500 deg$^2$ survey area with redshift up to $z\sim 4$, providing photometric and spectroscopic galaxy catalogs. In this work, we simulate the CSST galaxy catalogs and the 5-year GW data from the 3G GW detectors and combine them to infer the Hubble constant ($H_0$). Our results show that the measurement precision of $H_0$ could reach the sub-percent level, meeting the standard of precision cosmology. We conclude that the synergy between CSST and the 3G GW detectors is of great significance in measuring the Hubble constant.

astro-ph.CO↗
arXiv2023

Recovery of phase constant from two-photon interference pattern by phase retrieval algorithm

For a HOM interferometer with two independent incident pulses, the interference pattern can be affected by adding a dispersion medium on one of the incident directions, but there hasn't been a method to reconstruct the phase constant of the medium from the interference pattern. To solve it, we adapted two phase retrieval algorithms and used them to recover the phase difference function between the two incident fields, from which the phase constant can be derived. Through simulations, we verified the convergence, accuracy, and robustness of the algorithms, indicating that this phase recovery process can be completed well with negligible error. Our research finds a new application direction for the phase recovery algorithm, provides an algorithmic tool for high-order dispersion measurement using two-photon interference, and paves the way for a higher resolution and phase-sensitive quantum tomography.

quant-ph↗
arXiv2023

Sciences with the 2.5-meter Wide Field Survey Telescope (WFST)

The Wide Field Survey Telescope (WFST) is a dedicated photometric surveying facility being built jointly by the University of Science and Technology of China and the Purple Mountain Observatory. It is equipped with a 2.5-meter diameter primary mirror, an active optics system, and a mosaic CCD camera with 0.73 gigapixels on the primary focal plane for high-quality image capture over an FOV of 6.5-square-degree. It is anticipated that WFST will be set up at the Lenghu site in the summer of 2023 and begin to observe the northern sky in four optical bands (u, g, r, and i) with a range of cadences, from hourly/daily in the Deep High-Cadence Survey (DHS) program to semiweekly in the Wide-Field Survey (WFS) program, three months later. During a photometric night, a nominal 30 s exposure in the WFS program will reach a depth of 22.27, 23.32, 22.84, and 22.31 (AB magnitudes) in these four bands, respectively, allowing for the detection of a tremendous amount of transients in the low-z universe and a systematic investigation of the variability of Galactic and extragalactic objects. In the DHS program, intranight 90 s exposures as deep as 23 (u) and 24 mag (g), in combination with target of opportunity follow-ups, will provide a unique opportunity to explore energetic transients in demand for high sensitivities, including the electromagnetic counterparts of gravitational wave events, supernovae within a few hours of their explosions, tidal disruption events and fast, luminous optical transients even beyond a redshift of unity. In addition, the final 6-year co-added images, anticipated to reach g=25.8 mag in WFS or 1.5 mags deeper in DHS, will be of fundamental importance to general Galactic and extragalactic science. The highly uniform legacy surveys of WFST will serve as an indispensable complement to those of LSST that monitor the southern sky.

astro-ph.IM↗
arXiv2023

Detector induced anisotropies on the angular distribution of gravitational wave sources and opportunities of constraining horizon scale anisotropies

The cosmological principle has been verified using electromagnetic (EM) observations. However its verification with high accuracy is challenging due to various foregrounds and selection effects, and possible violation of the cosmological principle has been reported in the literature. In contrast, gravitational wave (GW) observations are free of these foregrounds and related selection biases. This may enable future GW experiments to test the cosmological principle robustly with full sky distribution of millions of standard bright/dark sirens. However, the sensitivities of GW detectors are highly anisotropic, resulting in significant instrument induced anisotropies in the observed GW catalog. We investigate these instrumental effects for 3rd generation detector networks in term of multipoles $a_{\ell m}$ of the observed GW source distribution, using Monte Carlo simulations. (1) We find that the instrument induced anisotropy primarily exists at the $m=0$ modes on large scales ($\ell \lesssim 10$), with amplitude $\langle |a_{\ell 0}|^2 \rangle \sim 10^{-3}$ for two detectors (ET-CE) and $\sim 10^{-4}$ for three detectors (ET-2CE). This anisotropy is correlated with the sky distribution of signal-to-noise ratio (SNR) and localization accuracy. Such anisotropy sets a lower limit on the detectable cosmological $a_{\ell 0}$. (2) However, we find that the instrument induced anisotropy is efficiently canceled by rotation of the Earth in $m\neq 0$ components of $a_{\ell m}$. Therefore $a_{\ell m}$ ($m\neq 0$) are clean windows to detect cosmological anisotropies. (3) We investigate the capability of 3rd generation GW experiments to measure the cosmic dipole. Through Monte Carlo simulations, we find that cosmic dipole with an amplitude of $\sim 10^{-2}$ reported in the literature can be detected/ruled out by ET-CE and ET-2CE robustly, through the measurement of $a_{11}$.

astro-ph.CO↗
arXiv2023

Multi-mode quantum correlation generated from an unbalanced SU(1,1) interferometer using ultra-short laser pulses as pump

Multi-mode entanglement is one of the critical resource in quantum information technology. Generating large scale multi-mode entanglement state by coherently combining time-delayed continuous variables Einstein-Podolsky-Rosen pairs with linear beam-splitters has been widely studied recently. Here we theoretically investigate the multi-mode quantum correlation property of the optical fields generated from an unbalanced SU(1,1) interferometer pumped ultra-short pulses, which generates multi-mode entangled state by using a non-degenerate parametric processes to coherently combine delayed Einstein-Podolsky-Rosen pairs in different frequency band. The covariance matrix of the generated multi-mode state is derived analytically for arbitrary mode number $M$ within adjacent timing slot, which shows a given mode is maximally correlated to 5 other modes. Based on the derived covariance matrix, both photon number correlation and quadrature amplitude correlation of the generated state is analyzed. We also extend our analyzing method to the scheme of generating entangled state by using linear beam splitter as a coherent combiner of delayed EPR pairs, and compare the states generated by the two coherently combining schemes. Our result provides a comprehensive theoretical description on the quantum correlations generated from an unbalanced SU(1,1) interferometer within Gaussian system range, and will offer more perspectives to quantum information technology.

quant-ph↗
arXiv2023

Constraints Based on Non-detection of Kilonova Optical Searching

Mergers of binary neutron stars are multimessenger sources of gravitational waves that have an optical luminous counterpart, commonly referred to as 'kilonova'. Inspired by the detection of GW170817, intensive searches have been conducted during the LIGO/Virgo O3 run. However, despite these efforts, no verified kilonova was detected. In this work, we present a parameter constraint method based on non-detection of optical searching considering both GW skymap, limited sky coverage, cadence, limiting magnitudes and the probability of astrophysical origin. We use our method to place constraints on EoS of neutron star based on follow-up during O3 run and obtain $M_{\rm TOV} = 2.170^{+0.120}_{-0.108}\ M_{\odot}$ at 90\% confidence level with the combination of other observations. And we also take outlook for WFST targeting kilonova throughout the LIGO/Virgo O4 run. With more events handled, we will obtain more stringent constraints on EoS and kilonova populations.

astro-ph.HE↗
arXiv2023

Gravitational waveforms from the inspiral of compact binaries in the Brans-Dicke theory in an expanding Universe

In modified gravity theories, such as the Brans-Dicke theory, the background evolution of the Universe and the perturbation around it are different from that in general relativity. Therefore, the gravitational waveforms used to study standard sirens in these theories should be modified. The modifications of the waveforms can be classified into two categories: wave generation effects and wave propagation effects. Hitherto, the waveforms used to study standard sirens in the modified gravity theories incorporate only the wave propagation effects and ignore the wave generation effects; while the waveforms focusing on the wave generation effects, such as the post-Newtonian waveforms, do not incorporate the wave propagation effects and cannot be directly applied to the sources with non-negligible redshifts in the study of standard sirens. In this work, we construct the consistent waveforms for standard sirens in the Brans-Dicke theory. The wave generation effects include the emission of the scalar breathing polarization $h_b$ and the corrections to the tensor polarizations $h_+$ and $h_\times$; the wave propagation effect is the modification of the luminosity distance for the gravitational waveforms. Using the consistent waveforms, we analyze the parameter estimation biases due to the ignorance of the wave generation effects. Considering the observations by the Einstein Telescope, we find that the ratio of the theoretical bias to the statistical error of the redshifted chirp mass is two orders of magnitude larger than that of the source distance. For black hole-neutron star binary systems like GW191219, the theoretical bias of the redshifted chirp mass can be several times larger than the statistical error.

gr-qc↗
arXiv2023

Evaluating ChatGPT's Information Extraction Capabilities: An Assessment of Performance, Explainability, Calibration, and Faithfulness

The capability of Large Language Models (LLMs) like ChatGPT to comprehend user intent and provide reasonable responses has made them extremely popular lately. In this paper, we focus on assessing the overall ability of ChatGPT using 7 fine-grained information extraction (IE) tasks. Specially, we present the systematically analysis by measuring ChatGPT's performance, explainability, calibration, and faithfulness, and resulting in 15 keys from either the ChatGPT or domain experts. Our findings reveal that ChatGPT's performance in Standard-IE setting is poor, but it surprisingly exhibits excellent performance in the OpenIE setting, as evidenced by human evaluation. In addition, our research indicates that ChatGPT provides high-quality and trustworthy explanations for its decisions. However, there is an issue of ChatGPT being overconfident in its predictions, which resulting in low calibration. Furthermore, ChatGPT demonstrates a high level of faithfulness to the original text in the majority of cases. We manually annotate and release the test sets of 7 fine-grained IE tasks contains 14 datasets to further promote the research. The datasets and code are available at https://github.com/pkuserc/ChatGPT_for_IE.

cs.CL↗
arXiv2023

Target of Opportunity Observations Detectability of Kilonovae with WFST

Kilonovae are approximately thermal transients, produced by mergers of binary neutron stars (BNSs) and NS-black hole binaries. As the optical counterpart of the gravitational wave event GW170817, AT2017gfo is the first kilonova detected with smoking-gun evidence. Its observation offers vital information for constraining the Hubble constant, the source of cosmic $r$-process enrichment, and the equation of state of neutron stars. The 2.5-meter Wide-Field Survey Telescope (WFST) operates at six bands (u, g, r, i, z, w), spanning from 320 to 925 nm. It will be completed in the first half of 2023, and with a field-of-view diameter of 3 degrees, aims to detect kilonovae in the near future. In this article, considering the influence of the host galaxies and sky brightness, we generate simulated images to investigate WFST's ability to detect AT2017gfo-like kilonovae. Due to their spectra, host galaxies can significantly impact kilonova detection at a longer wavelength. When kilonovae are at peak luminosity, we find that WFST performs better in the g and r bands and can detect 90\% (50\%) kilonovae at a luminosity distance of 248 Mpc (338 Mpc) with 30 s exposures. Furthermore, to reflect actual efficiency under target-of-opportunity observations, we calculate the total time of follow-up under various localization areas and distances. We find that if the localization areas of most BNS events detected during the fourth observing (O4) run of LIGO and Virgo are hundreds of deg$^2$, WFST is expected to find $\sim$30\% kilonovae in the first two nights during O4 period.

astro-ph.HE↗
arXiv2023

The luminosity functions of kilonovae from binary neutron star mergers under different equation of states

Kilonovae produced by mergers of binary neutron stars (BNSs) are important transient events to be detected by time domain surveys with the alerts from the ground-based gravitational wave detectors. The observational properties of these kilonovae depend on the physical processes involved in the merging processes and the equation of state (EOS) of neutron stars (NSs). In this paper, we investigate the dependence of kilonova luminosities on the parameters of BNS mergers, and estimate the distribution functions of kilonova peak luminosities (KLFs) at the u, g, r, i, y, and z bands as well as its dependence on the NS EOS, by adopting a comprehensive semi-analytical model for kilonovae (calibrated by the observations of GW170817), a population synthesis model for the cosmic BNSs, and the ejecta properties of BNS mergers predicted by numerical simulations. We find that the kilonova light curves depend on both the BNS properties and the NS EOS, and the KLFs at the considered bands are bimodal with the bright components mostly contributed by BNS mergers with total mass $\lesssim 3.2M_\odot$/$2.8M_\odot$ and fainter components mostly contributed by BNS mergers with total mass $\gtrsim 3.2M_\odot$/$2.8M_\odot$ by assuming a stiff/soft (DD2/SLy) EOS. The emission of the kilonovae in the KLF bright components is mostly due to the radiation from the wind ejecta by the remnant discs of BNS mergers, while the emission of the kilonovae in the KLF faint components is mostly due to the radiation from the dynamical ejecta by the BNS mergers.

astro-ph.HE↗
arXiv2023

Forecasts of CMB lensing reconstruction of AliCPT-1 from the foreground cleaned polarization data

Cosmic microwave background radiation (CMB) observations are unavoidably contaminated by emission from various extra-galactic foregrounds, which must be removed to obtain reliable measurements of the cosmological signal. In this paper, we demonstrate CMB lensing reconstruction in AliCPT-1 after foreground removal, combine the two bands of AliCPT-1 (90 and 150~GHz) with Planck HFI bands (100, 143, 217 and 353~GHz) and with the WMAP-K band (23~GHz). In order to balance contamination by instrumental noise and foreground residual bias, we adopt the Needlet Internal Linear Combination (NILC) method to clean the E-map and the constrained Internal Linear Combination (cILC) method to clean the B-map. The latter utilizes additional constraints on average frequency scaling of the dust and synchrotron to remove foregrounds at the expense of somewhat noisier maps. Assuming 4 modules observing 1 season from simulation data, the resulting effective residual noise in E- and B-map are roughly $15~μ{\rm K}\cdot{\rm arcmin}$ and $25~μ{\rm K}\cdot{\rm arcmin}$, respectively. As a result, the CMB lensing reconstruction signal-to-noise ratio (SNR) from polarization data is about SNR$\,\approx\,$4.5. This lensing reconstruction capability is comparable to that of other stage-III small aperture millimeter CMB telescopes.

astro-ph.CO↗
arXiv2023

Testing Lorentz Invariance of Gravity in the Standard Model Extension with GWTC-3

Successful detection of gravitational waves has presented a new avenue to explore the nature of gravity. With the cumulative catalog of detected events, we can perform tests on General Relativity from various aspects with increasing precision. In this work, we focus on Lorentz symmetry during propagation of gravitational waves. Considering the dispersion relation in the gauge-invariant linearized gravity sector of the Standard-Model Extension, the anisotropy, birefringence, and dispersion effects will be induced during propagation of gravitational waves because of the Lorentz violating modification, and cause dephasings in waveform received by detectors. With the distorted waveform, we perform full Bayesian inference with confident events in the last gravitational wave catalog. We consider two cases associated with the lowest mass dimension $d=5,6$ which are supposed to have the most significant effects, and place the constraints on the expansion coefficients characterizing the Lorentz violating behavior which have 16 independent components for $d=5$ and 18 components for $d=6$. We do not find any evidence for Lorentz violation in the gravitational wave data, the constraints on the coefficients are on the order of $10^{-15}{\rm m}$ for $d=5$ and $10^{-10}{\rm m^2}$ for $d=6$ respectively.

gr-qc↗
arXiv2023

Is the Observable Universe Consistent with the Cosmological Principle?

The Cosmological Principle (CP) -- the notion that the Universe is spatially isotropic and homogeneous on large scales -- underlies a century of progress in cosmology. It is conventionally formulated through the Friedmann-Lemaître-Robertson-Walker (FLRW) cosmologies as the spacetime metric, and culminates in the successful and highly predictive $Λ$-Cold-Dark-Matter ($Λ$CDM) model. Yet, tensions have emerged within the $Λ$CDM model, most notably a statistically significant discrepancy in the value of the Hubble constant, $H_0$. Since the notion of cosmic expansion determined by a single parameter is intimately tied to the CP, implications of the $H_0$ tension may extend beyond $Λ$CDM to the CP itself. This review surveys current observational hints for deviations from the expectations of the CP, highlighting synergies and disagreements that warrant further study. Setting aside the debate about individual large structures, potential deviations from the CP include variations of cosmological parameters on the sky, discrepancies in the cosmic dipoles, and mysterious alignments in quasar polarizations and galaxy spins. While it is possible that a host of observational systematics are impacting results, it is equally plausible that precision cosmology may have outgrown the FLRW paradigm, an extremely pragmatic but non-fundamental symmetry assumption.

astro-ph.CO↗
arXiv2023

Gravitational wave constraints on spatial covariant gravities

The direct discovery of gravitational waves (GWs) from the coalescence of compact binary components by the LIGO/Virgo/KAGRA Collaboration provides an unprecedented opportunity for exploring the underlying theory of gravity that drives the coalescence process in the strong and highly dynamical field regime of gravity. In this paper, we consider the observational effects of spatial covariant gravities on the propagation of GWs in the cosmological background and obtain the observational constraints on coupling coefficients in the action of spatial covariant gravities from GW observations. We first decompose the GWs into the left- and right-hand circular polarization modes and derive the effects of the spatial covariant gravities on the propagation equation of GWs. We find that these effects can be divided into three classes: 1) frequency-independent effects on GW speed and friction, 2) parity-violating amplitude and velocity birefringences, and 3) a Lorentz-violating damping rate and dispersion of GWs. With these effects, we calculate the corresponding modified waveform of GWs generated by the coalescence of compact binaries. By comparing these new effects with the publicly available posterior samples or results from various tests of gravities with LIGO/Virgo/KAGRA data in the literature, we derive the observational constraints on coupling coefficients of the spatial covariant gravities. These results represent the most comprehensive constraints on the spatial covariant gravities in the literature.

gr-qc↗
arXiv2023

Gravitational wave constraints on non-birefringent dispersions of gravitational waves due to Lorentz violations with GWTC-3

The standard model extension (SME) is an effective field theory framework that can be used to study the possible violations of Lorentz symmetry in the gravitational interaction. In the SME's gauge invariant linearized gravity sector, the dispersion relation of GWs is modified, resulting in anisotropy, birefringence, and dispersion effects in the propagation of GWs. In this paper, we mainly focus on the non-birefringent and anisotropic dispersion relation in the propagation of GWs due to the violation of Lorentz symmetry. With the modified dispersion relation, we calculate the corresponding modified waveform of GWs generated by the coalescence of compact binaries. We consider the effects from the operators with the lowest mass dimension $d=6$ in the gauge invariant linearized gravity sector of the SME which are expected to have the dominant Lorentz-violating effect on the propagation of GWs. For this case, the Lorentz-violating effects are presented by 25 coefficients and we constrain them independently by the ``maximal-reach" approach. We use 90 high-confidence GW events in the GWTC-3 catalog and use {\tt Bilby}, an open source software, and {\tt Dynest}, a nested sampling package, to perform parameter estimation with the modified waveform. We do not find any evidence of Lorentz violation in the GWs data and give a $90\%$ confidence interval for each Lorentz violating coefficient.

gr-qc↗