arXiv subjects

Shuaibo Geng

Publications and source records attributed to Shuaibo Geng.

14 recordsLinked to original sources

arXiv2026

Hierarchical cosmological constraints through strong lensing distance ratio

Strong gravitational lensing provides an independent and powerful probe of cosmic expansion by directly linking observables to cosmological distances. Upcoming surveys such as LSST will discover large number of galaxy-galaxy strong lensing systems, offering a new route to precise cosmological constraints. In this paper, we propose a Fisher-like sensitivity factor to map how the cosmological information of strong-lensing distances changes across the lens-source redshift plane. Applying such factor to the distance ratio $D_{ls}/D_s$, the time-delay distance $D_{Δt}$, and the double-source-plane ratio, we determine the ``sensitivity valleys'' where an observable becomes insensitive to a given parameter. The realistically simulated LSST lens population, which largely lies outside the distance-ratio valleys, covers the most sensitive region for $(w_0,w_a)$ parameter space. We then develop a new hierarchical framework, which could calibrate the redshift evolution of lens mass-density slopes and constrain cosmological parameters simultaneously. Focusing on the LSST mock data, we demonstrate that ignoring mass-profile evolution can bias $Ω_m$ by up to $\sim 10σ$, while modeling the lens evolution could perfectly recovers the fiducial cosmology and yield stringent cosmological constraints (e.g., $ΔΩ_m \simeq 0.01$ and $Δw \simeq 0.1$ for $\sim 10^4$ lenses).

astro-ph.CO↗

arXiv2025

Investigating the Redshift Evolution of Lensing Galaxy Density Slopes via Model-Independent Distance Ratios

Strong lensing systems, expected to be abundantly discovered by next-generation surveys, offer a powerful tool for studying cosmology and galaxy evolution. The connection between galaxy structure and cosmology through distance ratios highlights the need to examine the evolution of lensing galaxy mass density profiles. We propose a novel, dark energy-model-independent method to investigate the mass density slopes of lensing galaxies and their redshift evolution using an extended power-law (EPL) model. We employ a non-parametric approach based on Artificial Neural Networks (ANNs) trained on Type Ia Supernovae (SNIa) data to reconstruct distance ratios of strong lensing systems. These ratios are compared with theoretical predictions to estimate the evolution of EPL model parameters. Analyses conducted at three levels, including the combined sample, individual lenses, and binned groups, ensure robust and reliable estimates. A negative trend in the mass density slope with redshift is observed, quantified as $\partialγ/\partial z = -0.20 \pm 0.12$ under a triangular prior for anisotropy. This study demonstrates that the redshift evolution of density slopes in lensing galaxies can be determined independently of dark energy models. Simulations based on LSST Rubin Observatory forecasts, which anticipate 100,000 strong lenses, show that spectroscopic follow-up of just 10 percent of these systems can constrain the redshift evolution coefficient with uncertainty ($Δ\partialγ/\partial z$) to 0.021. This precision distinguishes evolving and non-evolving density slopes, providing new insights into galaxy evolution and cosmology.

astro-ph.CO↗

arXiv2021

The velocity dispersion function of early-type galaxies and its redshift evolution: the newest results from lens redshift test

The redshift distribution of galactic-scale lensing systems provides a laboratory to probe the velocity dispersion function (VDF) of early-type galaxies (ETGs) and measure the evolution of early-type galaxies at redshift z ~ 1. Through the statistical analysis of the currently largest sample of early-type galaxy gravitational lenses, we conclude that the VDF inferred solely from strong lensing systems is well consistent with the measurements of SDSS DR5 data in the local universe. In particular, our results strongly indicate a decline in the number density of lenses by a factor of two and a 20% increase in the characteristic velocity dispersion for the early-type galaxy population at z ~ 1. Such VDF evolution is in perfect agreement with the $Λ$CDM paradigm (i.e., the hierarchical build-up of mass structures over cosmic time) and different from "stellar mass-downsizing" evolutions obtained by many galaxy surveys. Meanwhile, we also quantitatively discuss the evolution of the VDF shape in a more complex evolution model, which reveals its strong correlation with that of the number density and velocity dispersion of early-type galaxies. Finally, we evaluate if future missions such as LSST can be sensitive enough to place the most stringent constraints on the redshift evolution of early-type galaxies, based on the redshift distribution of available gravitational lenses.

astro-ph.GA↗

arXiv2020

Model-independent constraints on cosmic curvature: implication from the future gravitational wave observation DECIGO

A model-independent test of the cosmic curvature parameter $Ω_k$ is very important in cosmology. In order to estimate cosmic curvature from cosmological probes like standard candles, one has to be able to measure the luminosity distance $D_L(z)$, it's derivative with respect to redshift $D'_L(z)$ and independently know the expansion rate $H(z)$ at the same redshift. In this paper, we study how such an idea could be implemented with the future generation of space-based DECi-hertz Interferometer Gravitational-wave Observatory (DECIGO), in combination with cosmic chronometers providing cosmology-independent $H(z)$ data. Our results show that for the Hubble diagram of simulated DECIGO data acting as a new type of standard siren, it would be able to constrain cosmic curvature with the precision of $ΔΩ_k= 0.09$ with the currently available sample of 31 measurements of Hubble parameters. In the framework of the third generation ground-based gravitational wave detectors, the spatial curvature is constrained to be $ΔΩ_k= 0.13$ for Einstein Telescope (ET). More interestingly, compared to other approaches aiming for model-independent estimations of spatial curvature, our analysis also achieves the reconstruction of the evolution of $Ω_k(z)$, in the framework of a model-independent method of Gaussian processes (GP) without assuming a specific form. Therefore, one can expect that the newly emerged gravitational wave astronomy can become useful in local measurements of cosmic curvature using distant sources.

astro-ph.CO↗

arXiv2020

Gravitational-wave constraints on the cosmic opacity at $z\sim 5$: forecast from space gravitational-wave antenna DECIGO

Since gravitational waves (GWs) propagate freely through a perfect fluid, coalescing compact binary systems as standard sirens allow to measure the luminosity distance directly and provide distance measurements unaffected by the cosmic opacity. DECi-hertz Interferometer Gravitational-wave Observatory (DECIGO) is a future Japanese space gravitational-wave antenna sensitive to frequency range between target frequencies of LISA and ground-based detectors. Combining the predicted future GW observations from DECIGO and three current popular astrophysical probes (HII regions, SNe Ia Pantheon sample, quasar sample) in electromagnetic (EM) domains, one would be able to probe the opacity of the Universe at different redshifts. In this paper, we show that the cosmic opacity parameter can be constrained to a high precision ($Δε\sim 10^{-2}$) out to high redshifts ($z\sim$5). In order to reconstruct the evolution of cosmic opacity without assuming any particular functional form of it, the cosmic opacity tests should be applied to individual redshift bins independently. Therefore, we also calculate the optical depth at individual redshifts and averaged $τ(z)$ within redshift bins. Our findings indicate that, compared with the results obtained from the HII galaxies and Pantheon SNe Ia, there is an improvement in precision when the quasar sample is considered. While non-zero optical depth is statistically significant only for redshift ranges $0<z<0.5$, $1<z<2$, and $2.5<z<3.5$, such tendency is different from that obtained in the framework of its parametrized form. Therefore the importance of cosmic-opacity test without a prescribed phenomenological function should be emphasized.

astro-ph.CO↗

arXiv2020

A model-independent constraint on the Hubble constant with gravitational waves from the Einstein Telescope

In this paper, we investigate the expected constraints on the Hubble constant from the gravitational-wave standard sirens, in a cosmological-model-independent way. In the framework of the well-known Hubble law, the GW signal from each detected binary merger in the local universe ($z<0.10$) provides a measurement of luminosity distance $D_L$ and thus the Hubble constant $H_0$. Focusing on the simulated data of gravitational waves from the third-generation gravitational wave detector (the Einstein Telescope, ET), combined with the redshifts determined from electromagnetic counter parts and host galaxies, one can expect the Hubble constant to be constrained at the precision of $\sim 10^{-2}$ with 20 well-observed binary neutron star (BNS) mergers. Additional standard-siren measurements from other types of future gravitational-wave sources (NS-BH and BBH) will provide more precision constraints of this important cosmological parameter. Therefore, we obtain that future measurements of the luminosity distances of gravitational waves sources will be much more competitive than the current analysis, which makes it expectable more vigorous and convincing constraints on the Hubble constant in a cosmological-model-independent way.

astro-ph.CO↗

arXiv2020

Model-independent constraints on cosmic curvature: implication from updated Hubble diagram of high-redshift standard candles

The cosmic curvature ($Ω_k$) is a fundamental parameter for cosmology. In this paper, we propose an improved model-independent method to constrain the cosmic curvature, which is geometrically related to the Hubble parameter $H(z)$ and luminosity distance $D_L(z)$. Using the currently largest $H(z)$ sample from the well-known cosmic chronometers, as well as the luminosity distance $D_L(z)$ from the relation between the UV and X-ray luminosities of 1598 quasars and the newly-compiled Pantheon sample including 1048 SNe Ia, 31 independent measurements of the cosmic curvature $Ω_k(z)$ can be expected covering the redshift range of $0.07<z<2$. Our estimation of $Ω_k(z)$ is fully compatible with flat Universe at the current level of observational precision. Meanwhile, we find that, for the Hubble diagram of 1598 quasars as a new type of standard candle, the spatial curvature is constrained to be $Ω_k=0.08\pm0.31$. For the latest Pantheon sample of SNe Ia observations, we obtain $Ω_k= -0.02\pm0.14$. Compared to other approaches aiming for model-independent estimations of spatial curvature, our analysis also achieves constraints with competitive precision. More interestingly, it is suggested that the reconstructed curvature $Ω_k$ is negative in the high redshift region, which is also consistent with the results from the model-dependent constraints in the literature. Such findings are confirmed by our reconstructed evolution of $Ω_k(z)$, in the framework of a model-independent method of Gaussian processes (GP) without assuming a specific form.

astro-ph.CO↗

arXiv2020

Testing the cosmic opacity at higher redshifts: implication from quasars with available UV and X-ray observations

In this paper, we present a cosmological model-independent test for the cosmic opacity at high redshifts ($z\sim5$). We achieve this with the opacity-dependent luminosity distances derived from nonlinear relation between X-ray and UV emissions of quasars, combined with two types of opacity-independent luminosity distances derived from the Hubble parameter measurements and simulated gravitational wave (GW) events achievable with the Einstein Telescope (ET). In the framework of two phenomenological parameterizations adopted to describe cosmic opacity at high redshifts, our main results show that a transparent universe is supported by the current observational data at 2$σ$ confidence level. However, the derived value of the cosmic opacity is slightly sensitive to the parametrization of $τ(z)$, which highlights the importance of choosing a reliable parametrization to describe the optical depth $τ(z)$ in the early universe. Compared with the previous works, the combination of the quasar data and the $H(z)$/GW observations in similar redshift ranges provides a novel way to confirm a transparent universe ($ε=0$ at higher redshifts $z\sim 5$), with an accuracy of $Δε\sim 10^{-2}$. More importantly, our findings indicate that a strong degeneracy between the cosmic opacity parameter and the parameters characterizing the $L_{UV}-L_X$ relation of quasars, which reinforces the necessity of proper calibration for such new type of high-redshift standard candle (in a cosmological model-independent way).

astro-ph.CO↗

arXiv2020

Quantum fluctuation of entanglement for accelerated two-level detectors

Quantum entanglement as the one of the most general quantum resources, can be quantified by von Neumann entropy. However, as we know, the von Neumann entropy is only statistical quantity or operator, it therefore has fluctuation. The quantum fluctuation of entanglement (QFE) between Unruh-Dewitt detector modeled by a two-level atom is investigated in a relativistic setting. The Unruh radiation and quantum fluctuation effects affect the precise measurement of quantum entanglement. Inspired by this we present how the relativistic motion effects QFE for two entangled Unruh-Dewitt detectors when one of them is accelerated and interacts with the neighbor external scalar field. We find that QFE first increases by the Unruh thermal noise and then suddenly decays when the acceleration reaches at a considerably large value, which indicates that relativistic effect will lead to non-negligible QFE effect. We also find that the initial QFE (without acceleration effect) is minimum with the maximally entangled state. Moreover, although QFE has a huge decay when the acceleration is greater than $\sim0.96$, concurrence also decays to a very low value, the ratio $ΔE/C$ therefore still large. According to the equivalence principle, our findings could be in principle applied to dynamics of QFE under the influence of gravitation field.

quant-ph↗

arXiv2020

Model-independent constraints on Lorentz invariance violation: implication from updated Gamma-ray burst observations

Astrophysical observations provide a unique opportunity to test possible signatures of Lorentz Invariance Violation (LIV), due to the high energies and long distances involved. In quantum theory of gravity, one may expect the modification of the dispersion relation between energy and momentum for photons, which can be probed with the time-lag (the arrival time delay between light curves in different energy bands) of Gamma-ray bursts (GRBs). In this paper, by using the detailed time-delay measurements of GRB 160625B at different energy bands, as well as 23 time-delay GRBs covering the redshifts range of $z=0.168-2.5$ (which were measured at different energy channels from the light curves), we propose an improved model-independent method (based on the newly-compiled sample of $H(z)$ measurements) to probe the energy-dependent velocity due to the modified dispersion relation for photons. In the framework of a more complex and reasonable theoretical expression to describe the time delays, our results imply that the intrinsic time lags can be better described with more GRBs time delay data. More importantly, through direct fitting of the time-delay measurements of a sample of GRBs, our limit on the LIV energy scale is comparable to that with unknown constant for the intrinsic time lag, much lower than the Planck energy scale in both linear LIV and quadratic LIV cases.

astro-ph.CO↗

arXiv2019

Exploring the "$L$--$σ$" relation of HII galaxies and giant extragalactic HII regions acting as standard candles

Cosmological applications of HII galaxies (HIIGx) and giant extragalactic HII regions (GEHR) to construct the Hubble diagram at higher redshifts require knowledge of the "$L$--$σ$" relation of the standard candles used. In this paper, we study the properties of a large sample of 156 sources (25 high-$z$ HII galaxies, 107 local HII galaxies, and 24 giant extragalactic HII regions) compiled by Terlevich et al.(2015). Using the the cosmological distances reconstructed through two new cosmology-independent methods, we investigate the correlation between the H$β$ emission-line luminosity $L$ and ionized-gas velocity dispersion $σ$. The method is based on non-parametric reconstruction using the measurements of Hubble parameters from cosmic clocks, as well as the simulated data of gravitational waves from the third-generation gravitational wave detector (the Einstein Telescope, ET), which can be considered as standard sirens. Assuming the emission-line luminosity versus ionized gas velocity dispersion relation, $\log L ($H$β) = α\log σ($H$β)+κ$, we find the full sample provides a tight constraint on the correlation parameters. However, similar analysis done on three different sub-samples seems to support the scheme of treating HII galaxies and giant extragalactic HII regions with distinct strategies. Using the corrected "$L$--$σ$" relation for the HII observational sample beyond the current reach of Type Ia supernovae, we obtain a value of the matter density parameter, $Ω_{m}=0.314\pm0.054$ (calibrated with standard clocks) and $Ω_{m}=0.311\pm0.049$ (calibrated with standard sirens), in the spatially flat $Λ$CDM cosmology.

astro-ph.CO↗

arXiv2019

Testing cosmic opacity with the combination of strongly lensed and unlensed supernova Ia

In this paper, we present a scheme to investigate the opacity of the Universe in a cosmological-model-independent way, with the combination of current and future measurements of type Ia supernova sample and galactic-scale strong gravitational lensing systems with SNe Ia acting as background sources. The observational data include the current newly-compiled SNe Ia data (Pantheon sample) and simulated sample of SNe Ia observed by the forthcoming Large Synoptic Survey Telescope (LSST) survey, which are taken for luminosity distances ($D_L$) possibly affected by the cosmic opacity, as well as strongly lensed SNe Ia observed by the LSST, which are responsible for providing the observed time-delay distance ($D_{Δt}$) unaffected by the cosmic opacity. Two parameterizations, $τ(z)=2βz$ and $τ(z)=(1+z)^{2β}-1$ are adopted for the optical depth associated to the cosmic absorption. Focusing on only one specific type of standard cosmological probe, this provides an original method to measure cosmic opacity at high precision. Working on the simulated sample of strongly lensed SNe Ia observed by the LSST in 10 year $z$-band search, our results show that, with the combination of the current newly-compiled SNe Ia data (Pantheon sample), there is no significant deviation from the transparency of the Universe at the current observational data level. Moreover, strongly lensed SNe Ia in a 10 year LSST $z$-band search would produce more robust constraints on the validity of cosmic transparency (at the precision of $Δβ=10^{-2}$), with a larger sample of unlensed SNe Ia detected in future LSST survey. We have also discussed the ways in which our methodology could be improved, with the combination of current and future available data in gravitational wave (GW) and electromagnetic (EM) domain.

astro-ph.CO↗

arXiv2019

Implications from simulated strong gravitational lensing systems: constraining cosmological parameters using Gaussian Processes

Strongly gravitational lensing systems (SGL) encodes cosmology information in source/lens distance ratios $\mathcal{D}_{\rm obs}=\mathcal{D}_{\rm ls}/\mathcal{D}_{\rm s}$, which can be used to precisely constrain cosmological parameters. In this paper, based on future measurements of 390 strong lensing systems from the forthcoming LSST survey, we have successfully reconstructed the distance ratio $\mathcal{D}_{\rm obs}$ (with the source redshift $z_s\sim 4.0$), directly from the data without assuming any parametric form. A recently developed method based on model-independent reconstruction approach, Gaussian Processes (GP) is used in our study of these strong lensing systems. Our results show that independent measurement of the matter density parameter ($Ω_m$) could be expected from such strong lensing statistics. More specifically, one can expect $Ω_m$ to be estimated at the precision of $ΔΩ_m\sim0.015$ in the concordance $Λ$CDM model, which provides comparable constraint on $Ω_m$ with Planck 2015 results. In the framework of the modified gravity theory (DGP), 390 detectable galactic lenses from future LSST survey would lead to stringent fits of $ΔΩ_m\sim0.030$. \textbf{Finally, we have discussed three possible sources of systematic errors (sample incompleteness, the determination of length of lens redshift bin, and the choice of lens redshift shells), and quantified their effects on the final cosmological constraints. Our results strongly indicate that future strong lensing surveys, with the accumulation of a larger and more accurate sample of detectable galactic lenses, will considerably benefit from the methodology described in this analysis. }

astro-ph.CO↗

arXiv2019

Implications of the lens redshift distribution of strong lensing systems: cosmological parameters and the global properties of early-type galaxies

In this paper, we assemble a well-defined sample of early-type gravitational lenses extracted from a large collection of 158 systems, and use the redshift distribution of galactic-scale lenses to test the standard cosmological model ($Λ$CDM) and the modified gravity theory (DGP). Two additional sub-samples are also included to account for possible selection effect introduced by the detectability of lens galaxies. Our results show that independent measurement of the matter density parameter ($Ω_m$) could be expected from such strong lensing statistics. Based on future measurements of strong lensing systems from the forthcoming LSST survey, one can expect $Ω_m$ to be estimated at the precision of $ΔΩ_m\sim 0.006$, which provides a better constraint on $Ω_m$ than \textit{Planck} 2015 results. Moreover, use the lens redshift test is also used to constrain the characteristic velocity dispersion of the lensing galaxies, which is well consistent with that derived from the optical spectroscopic observations. A parameter $f_E$ is adopted to quantify the relation between the lensing-based velocity dispersion and the corresponding stellar value. Finally, the accumulation of detectable galactic lenses from future LSST survey would lead to more stringent fits of $Δf_E\sim10^{-3}$, which encourages us to test the global properties of early-type galaxies at much higher accuracy.

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