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 ~ 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 H0could 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.

Taiji-TianQin-LISA network:Precisely measuring the Hubble constant using both bright and dark sirens

In the coming decades,the space-based gravitational-wave(GW)detectors such as Taiji,TianQin,and LISA are expected to form a network capable of detecting millihertz GWs emitted by the mergers of massive black hole binaries(MBHBs).In this work,we investigate the potential of GW standard sirens from the Taiji-TianQin-LISA network in constraining cosmological parameters.For the optimistic scenario in which electromagnetic(EM)counterparts can be detected,we predict the number of detectable bright sirens based on three different MBHB population models,i.e.,popⅢ,Q3d,and Q3nod.Our results show that the TaijiTianQin-LISA network alone could achieve a constraint precision of 0.9%for the Hubble constant,meeting the standard of precision cosmology.Moreover,the Taiji-TianQin-LISA network could effectively break the cosmological parameter degeneracies generated by the CMB data,particularly in the dynamical dark energy models.When combined with the CMB data,the joint CMB+Taiji-TianQin-LISA data offerσ(w)=0.036 in the wCDM model,which is close to the latest constraint result obtained from the CMB+SN data.We also consider a conservative scenario in which EM counterparts are not available.Due to the precise sky localizations of MBHBs by the Taiji-TianQin-LISA network,the constraint precision of the Hubble constant is expected to reach 1.2%.In conclusion,the GW standard sirens from the Taiji-TianQin-LISA network will play a critical role in helping solve the Hubble tension and shedding light on the nature of dark energy.

Gravitational wave standard sirens and cosmological parameter measurement

The first detection of gravitational waves (GWs) produced by the binary neutron star (BNS) merger in August 17, 2017[1] is fairly meaningful because it initiated the new era of multi-messenger astronomy. In this BNS merger event, we not only detected the gravitational waves.

Forecast for cosmological parameter estimation with gravitational-wave standard sirens from the LISA-Taiji network

LISA and Taiji are expected to form a space-based gravitational-wave(GW)detection network in the future.In this work,we make a forecast for the cosmological parameter estimation with the standard siren observation from the LISA-Taiji network.We simulate the standard siren data based on a scenario with configuration angle of 40°between LISA and Taiji.Three models for the population of massive black hole binary(MBHB),i.e.,popⅢ,Q3d,and Q3nod,are considered to predict the events of MBHB mergers.We find that,based on the LISA-Taiji network,the number of electromagnetic(EM)counterparts detected is almost doubled compared with the case of single Taiji mission.Therefore,the LISA-Taiji network’s standard siren observation could provide much tighter constraints on cosmological parameters.For example,solely using the standard sirens from the LISA-Taiji network,the constraint precision of H;could reach 1.3%.Moreover,combined with the CMB data,the GW-EM observation based on the LISA-Taiji network could also tightly constrain the equation of state of dark energy,e.g.,the constraint precision of w reaches about 4%,which is comparable with the result of CMB+BAO+SN.It is concluded that the GW standard sirens from the LISA-Taiji network will become a useful cosmological probe in understanding the nature of dark energy in the future.

基于Siren函数改进的循环神经网络机器阅读理解

由于现有的循环神经网络存在着梯度消失与梯度爆炸的问题,会影响模型精度。为提升机器阅读理解模型的效率,采用了一种新型正弦激活函数Siren函数,结合注意力机制对循环神经网络进行改进。使用循环神经网络对文本数据进行特征提取,同时引入注意力机制,可以进一步抓住文本中的重点信息。经由Siren激活函数层对神经网络的输出进行处理后,传递至Softmax层与全连接层返回问题所需答案。采用该网络所实现的机器阅读理解模型,相较于原有的模型在精准度上有大幅度提升。实验数据采用SQuAD英文问答数据集,在对比实验中,相较于仅使用注意力机制的RNN版DrQA模型,EM指数提升了6.1,F1指数提升了5.9,同时Siren函数也在与其他激活函数的对比实验中均取得了较好的效果。

磁-浮工艺在舞阳红山选厂的应用

舞阳矿业公司红山选矿厂入选赤铁矿原矿铁品位27.35%左右。根据该选厂原矿特点,结合国内其他选厂的赤铁矿选矿技术,应用磁-重-反浮选流程,获得了铁精矿品位63%以上、回收率58%以上的良好选别指标。

建立基本单位名录库构想

The paper points out the shortcomings of the existing name list database and forwards some good suggestions by using foreign experiences for reference.

SIRENE——欧洲铁路通讯上层服务系统

欧洲的铁路运输业拥有悠久的光荣传统,它以多年一贯的准时安全的服务为欧洲近百年来的繁荣作出了很大的贡献。但是近三十年来它的陆上运输霸主的地位受到了来自航空业及公路运输业的挑战。为保住霸主地位,适应新的形势发展及变化。

Joint constraints on cosmological parameters using future multi-band gravitational wave standard siren observations

Gravitational waves(GWs)from compact binary coalescences can be used as standard sirens to explore the cosmic expansion history.In the next decades,it is anticipated that we could obtain the multi-band GW standard siren data(from nanohertz to a few hundred hertz),which are expected to play an important role in cosmological parameter estimation.In this work,we provide,for the first time to the best of our knowledge,joint constraints on cosmological parameters using the future multi-band GW standard siren observations.We simulate the multi-band GW standard sirens based on the SKA-era pulsar timing array(PTA),Taiji observatory,and Cosmic Explorer(CE)to perform cosmological analysis.In theΛCDM model,we find that the joint PTA+Taiji+CE data could provide a tight constraint on the Hubble constant with a 0.5%precision.Moreover,PTA+Taiji+CE could break the cosmological parameter degeneracies generated by CMB,especially in the dynamical dark energy models.When combining the PTA+Taiji+CE data with the CMB data,the constraint precisions of?_(m)and H_(0)are 1.0%and 0.3%,respectively,meeting the standard of precision cosmology.The joint CMB+PTA+Taiji+CE data giveσ(_(w))=0.028 in the wCDM model andσ(w_(0))=0.11 andσ(w_(a))=0.32 in the w_(0)w_(a)CDM model,which are comparable with or close to the latest constraint results by CMB+BAO+SN.In conclusion,the future multi-band GW observations are expected to be used for exploring the nature of dark energy and measuring the Hubble constant.

Impacts of gravitational-wave standard siren observations from Einstein Telescope and Cosmic Explorer on weighing neutrinos in interacting dark energy models

Multi-messenger gravitational wave(GW)observation for binary neutron star merger events could provide a rather useful tool to explore the evolution of the Universe.In particular,for the third-generation GW detectors,i.e.the Einstein Telescope(ET)and the Cosmic Explorer(CE),proposed to be built in Europe and the U.S.,respectively,lots of GW standard sirens with known redshifts could be obtained,which would exert great impacts on the cosmological parameter estimation.The total neutrino mass could be measured by cosmological observations,but such a measurement is model-dependent and currently only gives an upper limit.In this work,we wish to investigate whether the GW standard sirens observed by ET and CE could help improve the constraint on the neutrino mass,in particular in the interacting dark energy(IDE)models.We find that the GW standard siren observations from ET and CE can only slightly improve the constraint on the neutrino mass in the IDE models,compared to the current limit.The improvements in the IDE models are weaker than those in the standard cosmological model.Although the limit on neutrino mass can only be slightly updated,the constraints on other cosmological parameters can be significantly improved by using the GW observations.

Constraining the Hubble constant to a precision of about 1% using multi-band dark standard siren detections

Gravitational wave signal from the inspiral of stellar-mass binary black hole can be used as standard sirens to perform cosmological inference.This inspiral covers a wide range of frequency bands,from the millihertz band to the audio-band,allowing for detections by both space-borne and ground-based gravitational wave detectors.In this work,we conduct a comprehensive study on the ability to constrain the Hubble constant using the dark standard sirens,or gravitational wave events that lack electromagnetic counterparts.To acquire the redshift information,we weight the galaxies within the localization error box with photometric information from several bands and use them as a proxy for the binary black hole redshift.We discover that Tian Qin is expected to constrain the Hubble constant to a precision of roughly 30%through detections of 10 gravitational wave events;in the most optimistic case,the Hubble constant can be constrained to a precision of<10%,assuming Tian Qin I+II.In the optimistic case,the multi-detector network of Tian Qin and LISA is capable of constraining the Hubble constant to within 5%precision.It is worth highlighting that the multi-band network of Tian Qin and Einstein Telescope is capable of constraining the Hubble constant to a precision of about 1%.We conclude that inferring the Hubble constant without bias from photo-z galaxy catalog is achievable,and we also demonstrate self-consistency using the P-P plot.On the other hand,high-quality spectroscopic redshift information is crucial for improving the estimation precision of Hubble constant.

Wife-Subduing Air Raid Siren Confiscated

德国的一对夫妇家中不和。为了让妻子屈服,73岁的Vladimir R.居然用 拉响警报的办法。妻子沉默了,而安装在屋顶上的警报却让四邻不安,最后警察 没收了此警报器。