arXiv subjects

Hai-Nan Lin

Publications and source records attributed to Hai-Nan Lin.

At least 37 records · Page 2Linked to original sources

arXiv2021

Machine learning forecasts of the cosmic distance duality relation with strongly lensed gravitational wave events

We use simulated strongly lensed gravitational wave events from the Einstein Telescope to demonstrate how the luminosity and angular diameter distances, $d_L(z)$ and $d_A(z)$ respectively, can be combined to test in a model independent manner for deviations from the cosmic distance duality relation and the standard cosmological model. In particular, we use two machine learning approaches, the Genetic Algorithms and Gaussian Processes, to reconstruct the mock data and we show that both approaches are capable of correctly recovering the underlying fiducial model and can provide percent-level constraints at intermediate redshifts when applied to future Einstein Telescope data.

astro-ph.CO↗

arXiv2020

Model-independently calibrating the luminosity correlations of gamma-ray bursts using deep learning

Gamma-ray bursts (GRBs) detected at high redshift can be used to trace the Hubble diagram of the Universe. However, the distance calibration of GRBs is not as easily as that of type Ia supernovae (SNe Ia). For the calibrating method based on the empirical luminosity correlations, there is an underlying assumption that the correlations should be universal over the whole redshift range. In this paper, we investigate the possible redshift dependence of six luminosity correlations with a completely model-independent deep learning method. We construct a network combining the Recurrent Neural Networks (RNN) and the Bayesian Neural Networks (BNN), where RNN is used to reconstruct the distance-redshift relation by training the network with the Pantheon compilation, and BNN is used to calculate the uncertainty of the reconstruction. Using the reconstructed distance-redshift relation of Pantheon, we test the redshift dependence of six luminosity correlations by dividing the full GRB sample into two subsamples (low-$z$ and high-$z$ subsamples), and find that only the $E_p-E_γ$ relation has no evidence for redshift dependence. We use the $E_p-E_γ$ relation to calibrate GRBs, and the calibrated GRBs give tight constraint on the flat $Λ$CDM model, with the best-fitting parameter $Ω_{\rm M}$=0.307$^{+0.065}_{-0.073}$.

astro-ph.CO↗

arXiv2020

Strongly lensed gravitational waves as the probes to test the cosmic distance duality relation

The cosmic distance relation (DDR) associates the angular diameters distance ($D_A$) and luminosity distance ($D_L$) by a simple formula, i.e., $D_L=(1+z)^2D_A$. The strongly lensed gravitational waves (GWs) provide a unique way to measure $D_A$ and $D_L$ simultaneously to the GW source, hence can be used as probes to test DDR. In this paper, we prospect the use of strongly lensed GW events from the future Einstein Telescope to test DDR. We write the possible deviation of DDR as $(1+z)^2D_A/D_L=η(z)$, and consider two different parametrizations of $η(z)$, namely, $η_1(z)=1+η_0 z$ and $η_2(z)=1+η_0 z/(1+z)$. Numerical simulations show that, with about 100 strongly lensed GW events observed by ET, the parameter $η_0$ can be constrained at $1.3\%$ and $3\%$ levels for the first and second parametrizations, respectively.

gr-qc↗

arXiv2020

A new method to test the cosmic distance duality relation using the strongly lensed gravitational waves

We propose a new method to test the cosmic distance duality relation using the strongly lensed gravitational waves. The simultaneous observations of image positions, the relative time delay between different images, the redshift measurements of lens and source, together with the mass modelling of the lens galaxy, provide the angular diameter distance to the gravitational wave source. On the other hand, from the observation of gravitational wave signals the luminosity distance to the source can be obtained. This is to our knowledge the first method to simultaneously measure both the angular diameter distance and luminosity distance from the same source. Thus, the strongly lensed gravitational waves provide a unique way to test the cosmic distance duality relation. With the construction of the third generation gravitational detectors such as the Einstein Telescope in the future, it is possible to test the cosmic distance duality relation at an accuracy of several percent.

gr-qc↗

arXiv2019

Scale-invariance in the repeating fast radio burst 121102

The statistical properties of the repeating fast radio burst FRB 121102 are investigated. We find that the cumulative distributions of fluence, flux density, total energy and waiting time can be well fitted by the bent power law. In addition, the probability density functions of fluctuations of fluence, flux density and total energy well follow the Tsallis $q$-Gaussian distribution. The $q$ values keep steady around $q\sim 2$ for different scale intervals, indicating a scale-invariant structure of the bursts. The statistical properties of FRB 121102 are very similar to that of the soft gamma repeater SGR J1550-5418. The underlying physical implications need to be further investigated.

astro-ph.HE↗

arXiv2019

The Dark Matter Profiles in the Milky Way

We investigate the dark matter profile of the Milky Way using the observed rotation curve data out to 100 kpc. The baryonic matter of the Milky Way is divided into bulge, disk and gas components, and each component is modelled using various possible mass profiles available in literature. The arbitrary combination of seven bulge profiles, four disk profiles and two gas profiles results in fifty-six baryon models. These baryon models are combined with one of the four dark matter profiles: Burkert profile, core-modified profile, pseudo-isothermal profile and NFW profile, to fit the observed rotation curve data. Results show that in general the NFW profile fits the data better than the Burkert profile, while the core-modified profile and the pseudo-isothermal profile are essentially ruled out. The best-fitting NFW model has the scale length $r_0=8.1\pm 0.7$ kpc, and the corresponding local density of dark matter is $ρ_{\rm dm}(R=R_\odot)=0.51\pm0.09~{\rm GeV}/{\rm cm}^3$.

astro-ph.GA↗

arXiv2019

Non-parametric reconstruction of dark energy and cosmic expansion from the Pantheon compilation of type Ia supernovae

The equation of state (EoS) of dark energy plays an important role in the evolution of the universe and arouses great interests in recent years. With the progress on observational technique, precise constraint on the EoS of dark energy becomes possible. In this paper, we reconstruct the EoS of dark energy and cosmic expansion using Gaussian processes (GP) from the most up-to-date Pantheon compilation of type Ia supernovae (SNe Ia), which consists of 1048 finely calibrated SNe Ia. The reconstructed EoS of dark energy has large uncertainty due to its dependence on the second order derivative of the construction. Adding the direct measurements of Hubble parameters $H(z)$ as an additional constraint on the first order derivative can partially reduce the uncertainty, but is still not precise enough to distinguish between evolving and constant dark energy. Besides, the results heavily rely on the prior of Hubble constant $H_0$. The $H_0$ value inferred from SNe+$H(z)$ without prior is $H_0=70.5\pm 0.5~{\textrm{km}~\textrm{s}^{-1}~\textrm{Mpc}^{-1}}$. Moreover, the matter density $Ω_M$ has an unnegligible effect on the reconstruction of dark energy. Therefore, more accurate determinations on $H_0$ and $Ω_M$ are needed to tightly constrain the EoS of dark energy.

gr-qc↗

arXiv2019

The prospects of gravitational waves on constraining the anisotropy of the Universe

The observation of GW150914 indicated a new independent measurement of the luminosity distance of a gravitational wave event. In this paper, we constrain the anisotropy of the Universe by using gravitational wave events. We simulate hundreds of events of binary neutron star merging that may be observed by Einstein Telescope. Full simulation for producing process of gravitational wave data is employed. We find that 200 of binary neutron star merging in redshift $(0,1)$ observed by Einstein Telescope may constrain the anisotropy with an accuracy comparable to the result from Union2.1 supernovae. This result shows that gravitational waves can be a powerful tool in investigating the cosmological anisotropy.

gr-qc↗

arXiv2018

Testing the anisotropy of the Universe with the distance duality relation

The distance duality relation (DDR) is valid in Riemannian spacetime. The astronomical data hint that the universe may have certain preferred direction. If the universe is described by anisotropic cosmological models based on Riemannian spacetime, then DDR still valid. If the anisotropy universe is described by other models which are not based on Riemannian spacetime, then DDR is violated. Thus, DDR could be used to test the validity of these anisotropic cosmological models. In this paper, we perform anisotropic DDR parametrization with the dipolar structures. The DDR is tested by comparing the luminosity distance from type-Ia supernovae (Union 2.1 and JLA compilations) and the angular diameter distance from strong gravitational lensing (SL) systems at the same redshift. It is shown that, the DDR is valid with the Union2.1 compilation, while is violated more than 1$σ$ confidence level with the JLA compilation. Additionally, we verify the statistical signification of our method with Monte Carlo simulations. Due to the large uncertainty of available data, no strong evidence is found to violate the DDR in the anisotropic models.

gr-qc↗

arXiv2018

An anti-correlation between barycentre offsets and velocity dispersion for highest overdensity subhalos in cosmological simulations

In this paper, we use two hydrodynamic simulations to study the barycentre offsets $r_{\rm off}$ between the entire halo and the gas or dark matter subhalo with largest overdensity. We restrict our analysis to those halos with large rescaled offsets, i.e. $r_{\rm off}/r_{200}\gtrsim 0.05$. The halos which are less massive and at higher redshifts are more likely to have larger $r_{\rm off}/r_{200}$. The 3D velocity dispersion of the subhalos with largest overdensity is found to have a similar mass and redshift dependence as $r_{\rm off}/r_{200}$. We also find that the gas subhalos with maximum overdensity and larger gas velocity dispersion $σ_{v}^{\rm ICM,sub}/σ_{200}$ tend to have smaller barycentre offsets $r_{\rm off}/r_{200}$. Similar result is found for the highest overdensity dark matter subhalos but with less significance. This anti-correlation is more significant for the snapshot $z=0$ than $z=0.2$ and $0.5$. The underlying physical mechanism for this anti-correlation remains to be explored.

astro-ph.GA↗

arXiv2018

Testing the variation of the fine structure constant with strongly lensed gravitational waves

The possible variation of the electromagnetic fine structure constant $α_e$ on cosmological scales arouses great interests in recent years. The strongly lensed gravitational waves and the electromagnetic counterparts could be used to test this variation. Under the assumption that the speed of photon could be modified, while the speed of GW is the same as GR predicated, and they both propagate in a flat Friedman-Robertson-Walker universe, we investigate the difference of time delays of the images and derive the upper bound of the variation of $α_e$. For a typical lensing system in the standard cosmological models, we obtain $B\cosθ\leq 1.85\times10^{-5}$, where $B$ is the dipolar amplitude and $θ$ is the angle between observation and the preferred direction. Our result is consistent with the most up-to-date observations on $α_e$. In addition, the observations of strongly lensed gravitational waves and the electromagnetic counterparts could be used to test which types of alternative theories of gravity can account for the variation of $α_e$.

gr-qc↗

arXiv2018

New constraints on the distance duality relation from the local data

The cosmic distance duality relation (DDR), which connects the angular diameter distance and luminosity distance through a simple formula $D_A(z)(1+z)^2/D_L(z)\equiv1$, is an important relation in cosmology. Therefore, testing the validity of DDR is of great importance. In this paper, we test the possible violation of DDR using the available local data including type Ia supernovae (SNe Ia), galaxy clusters and baryon acoustic oscillations (BAO). We write the modified DDR as $D_A(z)(1+z)^2/D_L(z)=η(z)$, and consider two different parameterizations of $η(z)$, namely $η_1(z)=1+η_0 z$ and $η_2(z)=1+η_0 z/(1+z)$. The luminosity distance from SNe Ia are compared with the angular diameter distance from galaxy clusters and BAO at the same redshift. Two different cluster data are used here, i.e. elliptical clusters and spherical clusters. The parameter $η_0$ is obtained using the Markov chain Monte Carlo methods. It is found that $η_0$ can be strictly constrained by the elliptical clusters + BAO data, with the best-fitting values $η_0=-0.04\pm 0.12$ and $η_0=-0.05\pm 0.22$ for the first and second parametrizations, respectively. However, the spherical clusters + BAO data couldn't strictly constrain $η_0$ due to the large intrinsic scatter. In any case studied here, no evidence for the violation of DDR is found.

astro-ph.CO↗

arXiv2018

Local probes strongly favor $Λ$CDM against power-law and $R_h=ct$ universe

We constrain three cosmological models, i.e. the concordance cold dark matter plus a cosmological constant ($Λ$CDM) model, Power-law (PL) model, and $R_h=ct$ model using the available local probes, which includes the JLA compilation of type-Ia supernovae (SNe Ia), the direct measurement of Hubble constant (H(z)), and the baryon acoustic oscillations (BAO). For $Λ$CDM model, we consider two different cases, i.e. zero and non-zero spatial curvature. We find that by using the JLA alone, it is indistinguishable between $Λ$CDM and PL models, but the $R_h=ct$ model is strongly disfavored. If we combine JLA+H(z), the $Λ$CDM model is strongly favored against the other two models. The combination of all the three datasets also supports $Λ$CDM as the best model. We also use the low-redshift ($z<0.2$) data to constrain the deceleration parameter using cosmography method, and find that only the $Λ$CDM model is consistent with cosmography. However, there is no strong evidence to distinguish between flat and non-flat $Λ$CDM models by using the local data alone.

astro-ph.CO↗

arXiv2018

Searching for a possible dipole anisotropy on acceleration scale with 147 rotationally supported galaxies

We report a possible dipole anisotropy on acceleration scale $g_†$ with 147 rotationally supported galaxies in local Universe. It is found that a monopole and dipole correction for the radial acceleration relation can better describe the SPARC data set. The monopole term is negligible but the dipole magnitude is significant. It is also found that the dipole correction is mostly induced by the anisotropy on the acceleration scale. The magnitude of $\hat{g}_†$-dipole reaches up to $0.25\pm0.04$, and its direction is aligned to $(l,b) = (171.30^{\circ}\pm7.18^{\circ}, -15.41^{\circ}\pm4.87^{\circ})$, which is very close to the maximum anisotropy direction from the hemisphere comparison method. Furthermore, robust check shows that the dipole anisotropy couldn't be reproduced by isotropic mock data set. However, it is still premature to claim that the Universe is anisotropic due to the small data samples and uncertainty in the current observations.

astro-ph.CO↗

arXiv2018

A tomographic test of cosmological principle using the JLA compilation of type Ia supernovae

We test the cosmological principle by fitting a dipolar modulation of distance modulus and searching for an evolution of this modulation with respect to cosmological redshift. Based on a redshift tomographic method, we divide the Joint Light-curve Analysis compilation of supernovae of type Ia into different redshift bins, and employ a Markov-Chain Monte-Carlo method to infer the anisotropic amplitude and direction in each redshift bin. However, we do not find any significant deviations from the cosmological principle, and the anisotropic amplitude is stringently constrained to be less than a few thousandths at $95\%$ confidence level.

astro-ph.CO↗

arXiv2018

Testing the anisotropy of the universe using the simulated gravitational wave events from advanced LIGO and Virgo

The detection of gravitational waves (GWs) provides a powerful tool to constrain the cosmological parameters. In this paper, we investigate the possibility of using GWs as standard sirens in testing the anisotropy of the universe. We consider the GW signals produced by the coalescence of binary black hole systems and simulate hundreds of GW events from the advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo. It is found that the anisotropy of the universe can be tightly constrained if the redshift of the GW source is precisely known. The anisotropic amplitude can be constrained with an accuracy comparable to the Union2.1 complication of type-Ia supernovae if $\gtrsim 400$ GW events are observed. As for the preferred direction, $\gtrsim 800$ GW events are needed in order to achieve the accuracy of Union2.1. With 800 GW events, the probability of pseudo anisotropic signals with an amplitude comparable to Union2.1 is negligible. These results show that GWs can provide a complementary tool to supernovae in testing the anisotropy of the universe.

astro-ph.CO↗

arXiv2017

Testing the distance duality relation using type Ia supernovae and ultracompact radio sources

We test the possible deviation of the cosmic distance duality relation $D_A(z)(1+z)^2/D_L(z)\equiv 1$ using the standard candles/rulers in a fully model-independent manner. Type-Ia supernovae are used as the standard candles to derive the luminosity distance $D_L(z)$, and ultra-compact radio sources are used as the standard rulers to obtain the angular diameter distance $D_A(z)$. We write the deviation of distance duality relation as $D_A(z)(1+z)^2/D_L(z)=η(z)$. Specifically, we use two parameterizations of $η(z)$, i.e. $η_1(z)=1+η_0 z$ and $η_2(z)=1+η_0 z/(1+z)$. The parameter $η_0$ is obtained using the Markov chain Monte Carlo methods by comparing $D_L(z)$ and $D_A(z)$ at the same redshift. The best-fitting results are $η_0=-0.06\pm 0.05$ and $-0.18\pm 0.16$ for the first and second parameterizations, respectively. Our results depend on neither the cosmological models, nor the matter contents or the curvature of the universe.

astro-ph.CO↗

arXiv2017

Scale-invariance in soft gamma repeaters

The statistical properties of the soft gamma repeater SGR J1550--5418 are investigated carefully. We find that the cumulative distributions of fluence, peak flux and duration can be well fitted by a bent power law, while the cumulative distribution of waiting time follows a simple power law. In particular, the probability density functions of fluctuations of fluence, peak flux, and duration have a sharp peak and fat tails, which can be well fitted by a $q$-Gaussian function. The $q$ values keep approximately steady for different scale intervals, indicating a scale-invariant structure of soft gamma repeaters. Those results support that the origin of soft gamma repeaters is crustquakes of neutron stars with extremely strong magnetic fields.

astro-ph.HE↗