Previous X-ray and optical studies of the galaxy cluster pair A222/223 suggested the possible presence of a=lamentary structure connecting the two clusters,a result that appears to be supported by subsequent weak-lens...Previous X-ray and optical studies of the galaxy cluster pair A222/223 suggested the possible presence of a=lamentary structure connecting the two clusters,a result that appears to be supported by subsequent weak-lensing analyses.This=lament has been reported to host a primordial warm-hot intergalactic medium,which existed prior to being heated by the interactions of the clusters.In this study,we made an attempt to examine the reported emission feature with data from an archival Suzaku observation,taking advantage of its low detector background.Because the emission is expected to be very weak,we=rst carefully examined all potential sources of“contamination,”and then modeled the residual emission.Due to large uncertainties,unfortunately,our results can neither con=rm the presence of the reported emission feature nor rule it out.We discuss the sources of uncertainties.展开更多
In this study,we used thef(T) gravity framework with the energy-momentum tensor for a perfect fluid to derive key cosmological parameters,including the Hubble parameter H,deceleration parameter q and Statefinder diagn...In this study,we used thef(T) gravity framework with the energy-momentum tensor for a perfect fluid to derive key cosmological parameters,including the Hubble parameter H,deceleration parameter q and Statefinder diagnostics.Model parameters were optimized using an R^(2) test,resulting in β=1.312_(-0.014)^(+0.013),ξ=1.273_(-0.0071)^(+0.0065) and H_(0)=72.60_(-0.49)^(+0.50),with an R^(2) of 0.9527.Our model aligns closely with the ACDM model and shows good performance based on AIC and BIC criteria.Analyzing the q(z) curve revealed the transition from deceleration to acceleration in the universe's expansion.Additionally,we examined pressure,energy density,and equation of state parameter for two models,f(T)=λT and f(T)=T+βT^(2),both aligning well with observational data.The r-s and r-q diagnostics further confirm our model's consistency with ΛCDM,making it a strong alternative for explaining cosmic expansion.The evolution of Ω(z) shows strong consistency with the ΛCDM model,with the Om parameter approaching 0.3 at lower redshifts and parameter uncertainties highlighting the model's reliability.展开更多
In this study,we investigate the potential of mark-weighted angular correlation functions,which integrateβ-cosmic-web classification with angular correlation function analysis to improve cosmological constraints.Usin...In this study,we investigate the potential of mark-weighted angular correlation functions,which integrateβ-cosmic-web classification with angular correlation function analysis to improve cosmological constraints.Using SDSS DR12 CMASS-NGC galaxies and mock catalogs withΩ_(m)varying from 0.25 to 0.40,we assess the discriminative power of different statistics via the average improvement in chi-squared,ΔX^(2),across six redshift bins.This metric quantifies how effectively each statistic distinguishes between different cosmological models.Incorporating cosmic-web weights leads to substantial improvements.Using statistics weighted by the mean neighbor distance(Dnei)increasesΔX^(2)by approximately 40%–130%,while applying inverse mean neighbor distance weighting(1/Dnei)yields even larger gains,boostingΔX^(2)by a factor of 2–3 compared to traditional unweighted angular statistics.These enhancements are consistent with previous 3D clustering results,demonstrating the superior sensitivity of theβ-weighted approaches.Our method,based on thin redshift slices,is particularly suitable for slitless surveys(e.g.,Euclid,CSST)where redshift uncertainties limit 3D analyses.This study also offers a framework for applying marked statistics to 2D angular clustering.展开更多
This work aims to investigate the different stability conditions of two scenarios of the inhomogeneous Lemaitre–Tolman–Bond model of the universe with holographic dark energy.We considered the Rényi and Tsallis...This work aims to investigate the different stability conditions of two scenarios of the inhomogeneous Lemaitre–Tolman–Bond model of the universe with holographic dark energy.We considered the Rényi and Tsallis holographic models of interacting dark energy.These holographic models are investigated using the IR cutoff that equals the Hubble horizon.Various stability conditions of these models have been investigated to understand how much these models can tell us about the recent and future epochs of the universe in comparison with the cosmological constant model,orΛCDM model.The conditions of violating the cosmological energy conditions have been studied.The evolution of the entropy and its first and second derivatives have been calculated and plotted for these holographic models.This gives an idea of how far these models satisfy the generalized second law of thermodynamics and hence have thermodynamical stability.The dynamical stability is studied for these evolved models,which give us glimpses of the dynamical stability at different phases of its evolution.We focus on investigating the stability in recent and near future times up to z≤-4.Further investigation of stability has been obtained by studying the evolved sound speed squared parameter for these models,which gave us a final and decisive evaluation of the stability of these models.展开更多
Major interactions are known to trigger star formation in galaxies and alter their color.We study the major interactions in filaments and sheets using SDSS data to understand the influence of large-scale environments ...Major interactions are known to trigger star formation in galaxies and alter their color.We study the major interactions in filaments and sheets using SDSS data to understand the influence of large-scale environments on galaxy interactions.We identify the galaxies in filaments and sheets using the local dimension and also find the major pairs residing in these environments.The star formation rate(SFR) and color of the interacting galaxies as a function of pair separation are separately analyzed in filaments and sheets.The analysis is repeated for three volume limited samples covering different magnitude ranges.The major pairs residing in the filaments show a significantly higher SFR and bluer color than those residing in the sheets up to the projected pair separation of~50 kpc.We observe a complete reversal of this behavior for both the SFR and color of the galaxy pairs having a projected separation larger than 50 kpc.Some earlier studies report that the galaxy pairs align with the filament axis.Such alignment inside filaments indicates anisotropic accretion that may cause these differences.We do not observe these trends in the brighter galaxy samples.The pairs in filaments and sheets from the brighter galaxy samples trace relatively denser regions in these environments.The absence of these trends in the brighter samples may be explained by the dominant effect of the local density over the effects of the large-scale environment.展开更多
We examine the possibility of applying the baryonic acoustic oscillation reconstruction method to improve the neutrino massΣm_νconstraint.Thanks to the Gaussianization of the process,we demonstrate that the reconstr...We examine the possibility of applying the baryonic acoustic oscillation reconstruction method to improve the neutrino massΣm_νconstraint.Thanks to the Gaussianization of the process,we demonstrate that the reconstruction algorithm could improve the measurement accuracy by roughly a factor of two.On the other hand,the reconstruction process itself becomes a source of systematic error.While the algorithm is supposed to produce the displacement field from a density distribution,various approximations cause the reconstructed output to deviate on intermediate scales.Nevertheless,it is still possible to benefit from this Gaussianized field,given that we can carefully calibrate the“transfer function”between the reconstruction output and theoretical displacement divergence from simulations.The limitation of this approach is then set by the numerical stability of this transfer function.With an ensemble of simulations,we show that such systematic error could become comparable to statistical uncertainties for a DESI-like survey and be safely neglected for other less ambitious surveys.展开更多
The improvements in the sensitivity of the gravitational wave(GW) network enable the detection of several large redshift GW sources by third-generation GW detectors. These advancements provide an independent method to...The improvements in the sensitivity of the gravitational wave(GW) network enable the detection of several large redshift GW sources by third-generation GW detectors. These advancements provide an independent method to probe the large-scale structure of the universe by using the clustering of the binary black holes(BBHs). The black hole catalogs are complementary to the galaxy catalogs because of large redshifts of GW events, which may imply that BBHs are a better choice than galaxies to probe the large-scale structure of the universe and cosmic evolution over a large redshift range. To probe the large-scale structure, we used the sky position of the BBHs observed by third-generation GW detectors to calculate the angular correlation function and the bias factor of the population of BBHs. This method is also statistically significant as 5000 BBHs are simulated. Moreover, for the third-generation GW detectors, we found that the bias factor can be recovered to within 33% with an observational time of ten years. This method only depends on the GW source-location posteriors;hence, it can be an independent method to reveal the formation mechanisms and origin of the BBH mergers compared to the electromagnetic method.展开更多
The size distributions of 2D and 3D Voronoi cells and of cells of Vp（2, 3）,--2D cut of 3D Voronoi diagram--are explored, with the slngle-parameter （re-scaled） gamma distribution playing a central role in the analy...The size distributions of 2D and 3D Voronoi cells and of cells of Vp（2, 3）,--2D cut of 3D Voronoi diagram--are explored, with the slngle-parameter （re-scaled） gamma distribution playing a central role in the analytical fitting. Observational evidence for a cellular universe is briefly reviewed. A simulated Vp（2, 3） map with galaxies lying on the cell boundaries is constructed to compare, as regards general appearance, with the observed CfA map of galaxies and voids, the parameters of the simulation being so chosen as to reproduce the largest observed void size.展开更多
We study the super-large-scale structures in the Sloan Digital Sky Survey by cluster analysis, and examine the geometry and the properties of the member galaxies. Two subsamples are selected from the SDSS, Subsample 1...We study the super-large-scale structures in the Sloan Digital Sky Survey by cluster analysis, and examine the geometry and the properties of the member galaxies. Two subsamples are selected from the SDSS, Subsample 1 at the celestial equator and Subsample 2 further north. In Subsample 1 we discover two compact super-large-scale structures： the Sloan Great Wall and the CfA Great Wall. The Sloan Great Wall, located at a median redshift of z= 0.07804, has a total length of about 433 Mpc and a mean galaxy density of about six times that of the whole sample. Most of its member galaxies are of medium size and brightness. The CfA Great Wall, located at a median redshift of z = 0.03058, has a total length of about 251 Mpc and includes large percentages of faint and small galaxies and relatively fewer early-type galaxies.展开更多
A new way of probing the large-scale structure of the universe is proposed. Space is partitioned into cells the shape of rhombic dodecahedron. The cells are labelled 'filled' or 'empty' according as th...A new way of probing the large-scale structure of the universe is proposed. Space is partitioned into cells the shape of rhombic dodecahedron. The cells are labelled 'filled' or 'empty' according as they contain galaxies or not. The cell size is so chosen as to have nearly equal numbers of filled and empty cells for the given galaxy sample. Two observables on each cell are definable: the number of its like neighbors, n1, and a two-suffixed topological type τ, the suffixes being the numbers of its like and unlike neighbor-groups. The frequency distributions of n1 and T in the observed set of filled (empty) cells are then considered as indicators of the morphology of the set. The method is applied to the CfA catalogue of galaxies as an illustration. Despite its limited size, the data offers evidence 1) that the empty cells are more strongly clustered than the filled cells, and 2) that the filled cells, but not the empty cells, have a tendency to occur in sheets. Further directions of development both in theory and application are indicated.展开更多
The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a di...The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a diameter of 1.1 m.JUST provides two Nasmyth platforms for placing science instruments.One Nasmyth focus fits a field of view of 10′and the other has an extended field of view of 1.2°with correction optics.A tertiary mirror is used to switch between the two Nasmyth foci.JUST will be installed at a site at Lenghu in Qinghai Province,China,and will conduct spectroscopic observations with three types of instruments to explore the dark universe,trace the dynamic universe,and search for exoplanets:(1)a multi-fiber(2000 fibers)medium-resolution spectrometer(R=4000-5000)to spectroscopically map galaxies and large-scale structure;(2)an integral field unit(IFU)array of 500 optical fibers and/or a long-slit spectrograph dedicated to fast follow-ups of transient sources for multi-messenger astronomy;(3)a high-resolution spectrometer(R~100000)designed to identify Jupiter analogs and Earth-like planets,with the capability to characterize the atmospheres of hot exoplanets.展开更多
Using a uniform partitioning of cubic cells,we cover the total volume of aΛCDM cosmological simulation based on particles.We define a visualization cell as a spatial extension of the cubic cell,so that we collect all...Using a uniform partitioning of cubic cells,we cover the total volume of aΛCDM cosmological simulation based on particles.We define a visualization cell as a spatial extension of the cubic cell,so that we collect all simulation particles contained in this visualization cell to create a series of Cartesian plots in which the overdensity of matter is clearly visible.We then use these plots as input to a convolutional neural network(CNN)based on the Keras library and TensorFlow for image classification.To assign a class to each plot,we approximate the Hessian of the gravitational potential in the center of the cubic cells.Each selected cubic cell is then assigned a label of 1,2 or 3,depending on the number of positive eigenvalues obtained for the Householder reduction of the Hessian matrix.We apply the CNN to several models,including two models with different visualization volumes,one with a cell size of type L(large)and the other with a cell type S(small).A third model combines the plots of the previous L and S cell types.So far,we have mainly considered a slice parallel to the XY plane to make the plots.The last model is considered based on visualizations of cells that also include slices parallel to the ZX and ZY planes.We find that the accuracy in classification plots is acceptable,and the ability of the models to predict the class works well.These results allow us to demonstrate the aim of this paper,namely that the usual Cartesian plots contain enough information to identify the observed structures of the cosmic web.展开更多
Gamma-ray bursts(GRBs) are among the brightest objects in the Universe and, hence, can be observed up to a very high redshift. Properly calibrated empirical correlations between intensity and spectral correlations of ...Gamma-ray bursts(GRBs) are among the brightest objects in the Universe and, hence, can be observed up to a very high redshift. Properly calibrated empirical correlations between intensity and spectral correlations of GRBs can be used to estimate the cosmological parameters. However, the possibility of the evolution of GRBs with redshift is a long-standing puzzle. In this work, we used 162 long-duration GRBs to determine whether GRBs below and above a certain redshift have different properties. The GRBs are split into two groups, and we fit the Amati relation for each group separately. Our findings demonstrate that estimations of the Amati parameters for the two groups are substantially dissimilar. We perform simulations to investigate whether the selection effects could cause the difference. Our analysis shows that the differences may be either intrinsic or due to systematic errors in the data, and the selection effects are not their true origin. However, in-depth analysis with a new data set comprised of 119 long GRBs shows that intrinsic scatter may partly be responsible for such effects.展开更多
A significant excess of the stellar mass density at high redshift has been discovered from the early data release of James Webb Space Telescope(JWST),and it may require a high star formation efficiency.However,this wi...A significant excess of the stellar mass density at high redshift has been discovered from the early data release of James Webb Space Telescope(JWST),and it may require a high star formation efficiency.However,this will lead to large number density of ionizing photons in the epoch of reionization(EoR),so that the reionization history will be changed,which can arise tension with the current EoR observations.Warm dark matter(WDM),via the free streaming effect,can suppress the formation of small-scale structure as well as low-mass galaxies.This provides an effective way to decrease the ionizing photons when considering a large star formation efficiency in high-z massive galaxies without altering the cosmic reionization history.On the other hand,the constraints on the properties of WDM can be derived from the JWST observations.In this work,we study WDM as a possible solution to reconcile the JWST stellar mass density of high-z massive galaxies and reionization history.We find that,the JWST high-z comoving cumulative stellar mass density alone has no significant preference for either CDM or WDM model.But using the observational data of other stellar mass density measurements and reionization history,we obtain that the WDM particle mass with mw=0.51_(-0.12)^(+0.22) keV and star formation efficiency parameter f_(*)^(0)> 0.39 in 2σ confidence level can match both the JWST high-z comoving cumulative stellar mass density and the reionization history.展开更多
We develop methods to extract key dark energy information from cosmic distance measurements including the BAO scales and supernova(SN) luminosity distances.Demonstrated using simulated data sets of the complete DESI,L...We develop methods to extract key dark energy information from cosmic distance measurements including the BAO scales and supernova(SN) luminosity distances.Demonstrated using simulated data sets of the complete DESI,LSST and Roman surveys designed for BAO and SN distance measurements,we show that using our method,the dynamical behavior of the energy,pressure,equation of state(with its time derivative) of dark energy and the cosmic deceleration function can all be accurately recovered from high-quality data,which allows for robust diagnostic tests for dark energy models.展开更多
Three mechanisms for an alternative to the Doppler effect as an explanation for the redshift are reviewed. A fourth mechanism is the attenuation of the light as given by the Beer-Lambert law. The average value of the ...Three mechanisms for an alternative to the Doppler effect as an explanation for the redshift are reviewed. A fourth mechanism is the attenuation of the light as given by the Beer-Lambert law. The average value of the Hubble constant is therefore derived by processing the galaxies of the NED-D catalog in which the distances are independent of the redshift. The observed anisotropy of the Hubble constant is reproduced by adopting a rim model, a chord model, and both 2D and 3D Voronoi diagrams.展开更多
We analyze a simple model for tired light in a cosmological environment, a generalized model, and a spectroscopic model. The three models are tested on different compilations for the distance modulus of supernovae. Th...We analyze a simple model for tired light in a cosmological environment, a generalized model, and a spectroscopic model. The three models are tested on different compilations for the distance modulus of supernovae. The tests are negative for the simple tired light and the spectroscopic models, but positive for the generalized tired light model. The percentage error of the distance modulus for the generalized tired light model compared with the distance modulus of standard cosmology is less than one percent over the considered ranges in redshift.展开更多
This paper presents the development of a conceptual model of the universe,grounded in the Fine Structure Constant(α≈137.036).The Extended Fine Structure Constant(eFSC)Model exploresαas a function of twin prime mi-c...This paper presents the development of a conceptual model of the universe,grounded in the Fine Structure Constant(α≈137.036).The Extended Fine Structure Constant(eFSC)Model exploresαas a function of twin prime mi-croverses(U{137},whereα=137,and U{139},whereα=139),each defined by n-dimensional sets of prime numbers.Property counts for U{137}and U{139}are used in a modified Difference over Sum(DoS)calculation to ap-proximate the fractional component ofα,yielding a Relative Electromagnetic Force(EMF)value ofαII=0.036.Applying this method to additional twin prime pairs produces a distribution of EMF values that reflect the energy pro-files of known Standard Model forces,identifying the strong force as a triad of overlapping EM interactions,and linking the weak force to particle transitions involving neutrons,protons,electrons,and neutrinos.The model provides a conceptual framework for investigating the Higgs mechanism,quantum or-bital structures,quantum entanglement,and potential explanations for grav-ity,dark matter,dark energy,and time dilation.While not intended to supplant any existing physics,the eFSC Model offers a novel,prime-number-based archi-tecture for interpreting the quantum universe through a classical lens.展开更多
The mass window of ultralight axion dark matter motivated by suppressing the growth of structure on subgalactic scales,m~10-22eV,is now severely constrained by various observation data(e.g.,Lyman-αforest).As an attem...The mass window of ultralight axion dark matter motivated by suppressing the growth of structure on subgalactic scales,m~10-22eV,is now severely constrained by various observation data(e.g.,Lyman-αforest).As an attempt to reopen this mass window,we investigate an alternative ultralight dark matter candidate,the complex scalar field dark matter(SFDM).We derive the relativistic hydrodynamics of the complex SFDM in the framework of cosmological perturbation theory.Our formalism contains two novel ingredients uniquely associated with the complex SFDM model:the Eckart frame defined by the conserved Noether current,and the stiff gauge condition,c_(s)^(2)≡(δP/δρ)|s=1.In the Eckart frame,the complex SFDM is effectively an imperfect fluid with a dissipative energy flux,distinguishing itself from axion dark matter.The energy flux can affect the growth of density fluctuations dynamically.Meanwhile,we apply the stiff gauge condition to find new constitutive equations for the complex SFDM.We revisit the homogeneous evolution of the complex SFDM and present illustrative early-stage solutions for perturbations of the complex SFDM in a simplified setting.We demonstrate the effects of varying the model parameters on the evolution of the perturbation variables.展开更多
We present a GPU-accelerated cosmological simulation code,PhotoNs-GPU,based on an algorithm of Particle Mesh Fast Multipole Method(PM-FMM),and focus on the GPU utilization and optimization.A proper interpolated method...We present a GPU-accelerated cosmological simulation code,PhotoNs-GPU,based on an algorithm of Particle Mesh Fast Multipole Method(PM-FMM),and focus on the GPU utilization and optimization.A proper interpolated method for truncated gravity is introduced to speed up the special functions in kernels.We verify the GPU code in mixed precision and different levels of the interpolated method on GPU.A run with single precision is roughly two times faster than double precision for current practical cosmological simulations.But it could induce an unbiased small noise in power spectrum.Compared with the CPU version of PhotoNs and Gadget-2,the efficiency of the new code is significantly improved.Activated all the optimizations on the memory access,kernel functions and concurrency management,the peak performance of our test runs achieves 48%of the theoretical speed and the average performance approaches to~35%on GPU.展开更多
基金supported in part by the National Natural Science Foundation of China through Grant 11821303by the Ministry of Science and Technology of China through Grant 2018YFA0404502+1 种基金support from the China Scholarship Councilthe nancial support of the GA?R EXPRO grant No.21-13491X.
文摘Previous X-ray and optical studies of the galaxy cluster pair A222/223 suggested the possible presence of a=lamentary structure connecting the two clusters,a result that appears to be supported by subsequent weak-lensing analyses.This=lament has been reported to host a primordial warm-hot intergalactic medium,which existed prior to being heated by the interactions of the clusters.In this study,we made an attempt to examine the reported emission feature with data from an archival Suzaku observation,taking advantage of its low detector background.Because the emission is expected to be very weak,we=rst carefully examined all potential sources of“contamination,”and then modeled the residual emission.Due to large uncertainties,unfortunately,our results can neither con=rm the presence of the reported emission feature nor rule it out.We discuss the sources of uncertainties.
文摘In this study,we used thef(T) gravity framework with the energy-momentum tensor for a perfect fluid to derive key cosmological parameters,including the Hubble parameter H,deceleration parameter q and Statefinder diagnostics.Model parameters were optimized using an R^(2) test,resulting in β=1.312_(-0.014)^(+0.013),ξ=1.273_(-0.0071)^(+0.0065) and H_(0)=72.60_(-0.49)^(+0.50),with an R^(2) of 0.9527.Our model aligns closely with the ACDM model and shows good performance based on AIC and BIC criteria.Analyzing the q(z) curve revealed the transition from deceleration to acceleration in the universe's expansion.Additionally,we examined pressure,energy density,and equation of state parameter for two models,f(T)=λT and f(T)=T+βT^(2),both aligning well with observational data.The r-s and r-q diagnostics further confirm our model's consistency with ΛCDM,making it a strong alternative for explaining cosmic expansion.The evolution of Ω(z) shows strong consistency with the ΛCDM model,with the Om parameter approaching 0.3 at lower redshifts and parameter uncertainties highlighting the model's reliability.
基金supported by the Ministry of Science and Technology of China(2020SKA0110401,2020SKA0110402 and 2020SKA0110100)the National Key Research and Development Program of China(2018YFA0404504,2018YFA0404601 and 2020YFC2201600)+2 种基金the National Natural Science Foundation of China(12373005,11890691,12205388,12220101003 and 12473097)the China Manned Space Project with numbers CMS-CSST-2021(A02,A03,B01)Guangdong Basic and Applied Basic Research Foundation(2024A1515012309)。
文摘In this study,we investigate the potential of mark-weighted angular correlation functions,which integrateβ-cosmic-web classification with angular correlation function analysis to improve cosmological constraints.Using SDSS DR12 CMASS-NGC galaxies and mock catalogs withΩ_(m)varying from 0.25 to 0.40,we assess the discriminative power of different statistics via the average improvement in chi-squared,ΔX^(2),across six redshift bins.This metric quantifies how effectively each statistic distinguishes between different cosmological models.Incorporating cosmic-web weights leads to substantial improvements.Using statistics weighted by the mean neighbor distance(Dnei)increasesΔX^(2)by approximately 40%–130%,while applying inverse mean neighbor distance weighting(1/Dnei)yields even larger gains,boostingΔX^(2)by a factor of 2–3 compared to traditional unweighted angular statistics.These enhancements are consistent with previous 3D clustering results,demonstrating the superior sensitivity of theβ-weighted approaches.Our method,based on thin redshift slices,is particularly suitable for slitless surveys(e.g.,Euclid,CSST)where redshift uncertainties limit 3D analyses.This study also offers a framework for applying marked statistics to 2D angular clustering.
文摘This work aims to investigate the different stability conditions of two scenarios of the inhomogeneous Lemaitre–Tolman–Bond model of the universe with holographic dark energy.We considered the Rényi and Tsallis holographic models of interacting dark energy.These holographic models are investigated using the IR cutoff that equals the Hubble horizon.Various stability conditions of these models have been investigated to understand how much these models can tell us about the recent and future epochs of the universe in comparison with the cosmological constant model,orΛCDM model.The conditions of violating the cosmological energy conditions have been studied.The evolution of the entropy and its first and second derivatives have been calculated and plotted for these holographic models.This gives an idea of how far these models satisfy the generalized second law of thermodynamics and hence have thermodynamical stability.The dynamical stability is studied for these evolved models,which give us glimpses of the dynamical stability at different phases of its evolution.We focus on investigating the stability in recent and near future times up to z≤-4.Further investigation of stability has been obtained by studying the evolved sound speed squared parameter for these models,which gave us a final and decisive evaluation of the stability of these models.
基金financial support from the SERB,DST,Government of India through the project CRG/2019/001110IUCAA,Pune for providing support through an associateship program+1 种基金IISER Tirupati for support through a postdoctoral fellowshipFunding for the SDSS and SDSS-Ⅱhas been provided by the Alfred P.Sloan Foundation,the U.S.Department of Energy,the National Aeronautics and Space Administration,the Japanese Monbukagakusho,the Max Planck Society,and the Higher Education Funding Council for England。
文摘Major interactions are known to trigger star formation in galaxies and alter their color.We study the major interactions in filaments and sheets using SDSS data to understand the influence of large-scale environments on galaxy interactions.We identify the galaxies in filaments and sheets using the local dimension and also find the major pairs residing in these environments.The star formation rate(SFR) and color of the interacting galaxies as a function of pair separation are separately analyzed in filaments and sheets.The analysis is repeated for three volume limited samples covering different magnitude ranges.The major pairs residing in the filaments show a significantly higher SFR and bluer color than those residing in the sheets up to the projected pair separation of~50 kpc.We observe a complete reversal of this behavior for both the SFR and color of the galaxy pairs having a projected separation larger than 50 kpc.Some earlier studies report that the galaxy pairs align with the filament axis.Such alignment inside filaments indicates anisotropic accretion that may cause these differences.We do not observe these trends in the brighter galaxy samples.The pairs in filaments and sheets from the brighter galaxy samples trace relatively denser regions in these environments.The absence of these trends in the brighter samples may be explained by the dominant effect of the local density over the effects of the large-scale environment.
基金the support from the science research grants from the China Manned Space Project with NO.CMS-CSST-2021-B01supported by the World Premier International Research Center Initiative(WPI),MEXT,Japan+12 种基金the Ontario Research Fund:Research Excellence Program(ORF-RE)Natural Sciences and Engineering Research Council of Canada(NSERC)[funding reference number RGPIN-2019-067,CRD 523638-201,555585-20]Canadian Institute for Advanced Research(CIFAR)Canadian Foundation for Innovation(CFI)the National Natural Science Foundation of China(NSFC,Grant No.11929301)Simons FoundationThoth Technology IncAlexander von Humboldt Foundationthe Niagara supercomputers at the SciNet HPC Consortiumthe Canada Foundation for Innovationthe Government of OntarioOntario Research Fund—Research Excellencethe University of Toronto。
文摘We examine the possibility of applying the baryonic acoustic oscillation reconstruction method to improve the neutrino massΣm_νconstraint.Thanks to the Gaussianization of the process,we demonstrate that the reconstruction algorithm could improve the measurement accuracy by roughly a factor of two.On the other hand,the reconstruction process itself becomes a source of systematic error.While the algorithm is supposed to produce the displacement field from a density distribution,various approximations cause the reconstructed output to deviate on intermediate scales.Nevertheless,it is still possible to benefit from this Gaussianized field,given that we can carefully calibrate the“transfer function”between the reconstruction output and theoretical displacement divergence from simulations.The limitation of this approach is then set by the numerical stability of this transfer function.With an ensemble of simulations,we show that such systematic error could become comparable to statistical uncertainties for a DESI-like survey and be safely neglected for other less ambitious surveys.
基金supported by the National Natural Science Foundation of China (grant Nos. 11922303, 119201003 and 12021003)supported by Hubei province Natural Science Fund for the Distinguished Young Scholars (No.2019CFA052)supported by CAS Project for Young Scientists in Basic Research YSBR-006。
文摘The improvements in the sensitivity of the gravitational wave(GW) network enable the detection of several large redshift GW sources by third-generation GW detectors. These advancements provide an independent method to probe the large-scale structure of the universe by using the clustering of the binary black holes(BBHs). The black hole catalogs are complementary to the galaxy catalogs because of large redshifts of GW events, which may imply that BBHs are a better choice than galaxies to probe the large-scale structure of the universe and cosmic evolution over a large redshift range. To probe the large-scale structure, we used the sky position of the BBHs observed by third-generation GW detectors to calculate the angular correlation function and the bias factor of the population of BBHs. This method is also statistically significant as 5000 BBHs are simulated. Moreover, for the third-generation GW detectors, we found that the bias factor can be recovered to within 33% with an observational time of ten years. This method only depends on the GW source-location posteriors;hence, it can be an independent method to reveal the formation mechanisms and origin of the BBH mergers compared to the electromagnetic method.
文摘The size distributions of 2D and 3D Voronoi cells and of cells of Vp（2, 3）,--2D cut of 3D Voronoi diagram--are explored, with the slngle-parameter （re-scaled） gamma distribution playing a central role in the analytical fitting. Observational evidence for a cellular universe is briefly reviewed. A simulated Vp（2, 3） map with galaxies lying on the cell boundaries is constructed to compare, as regards general appearance, with the observed CfA map of galaxies and voids, the parameters of the simulation being so chosen as to reproduce the largest observed void size.
基金Supported by the National Natural Science Foundation of China
文摘We study the super-large-scale structures in the Sloan Digital Sky Survey by cluster analysis, and examine the geometry and the properties of the member galaxies. Two subsamples are selected from the SDSS, Subsample 1 at the celestial equator and Subsample 2 further north. In Subsample 1 we discover two compact super-large-scale structures： the Sloan Great Wall and the CfA Great Wall. The Sloan Great Wall, located at a median redshift of z= 0.07804, has a total length of about 433 Mpc and a mean galaxy density of about six times that of the whole sample. Most of its member galaxies are of medium size and brightness. The CfA Great Wall, located at a median redshift of z = 0.03058, has a total length of about 251 Mpc and includes large percentages of faint and small galaxies and relatively fewer early-type galaxies.
文摘A new way of probing the large-scale structure of the universe is proposed. Space is partitioned into cells the shape of rhombic dodecahedron. The cells are labelled 'filled' or 'empty' according as they contain galaxies or not. The cell size is so chosen as to have nearly equal numbers of filled and empty cells for the given galaxy sample. Two observables on each cell are definable: the number of its like neighbors, n1, and a two-suffixed topological type τ, the suffixes being the numbers of its like and unlike neighbor-groups. The frequency distributions of n1 and T in the observed set of filled (empty) cells are then considered as indicators of the morphology of the set. The method is applied to the CfA catalogue of galaxies as an illustration. Despite its limited size, the data offers evidence 1) that the empty cells are more strongly clustered than the filled cells, and 2) that the filled cells, but not the empty cells, have a tendency to occur in sheets. Further directions of development both in theory and application are indicated.
基金This work is supported by“the Fundamental Research Funds for the Central Universities”,111 project No.B20019Shanghai Natural Science Foundation,grant No.19ZR1466800.
文摘The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a diameter of 1.1 m.JUST provides two Nasmyth platforms for placing science instruments.One Nasmyth focus fits a field of view of 10′and the other has an extended field of view of 1.2°with correction optics.A tertiary mirror is used to switch between the two Nasmyth foci.JUST will be installed at a site at Lenghu in Qinghai Province,China,and will conduct spectroscopic observations with three types of instruments to explore the dark universe,trace the dynamic universe,and search for exoplanets:(1)a multi-fiber(2000 fibers)medium-resolution spectrometer(R=4000-5000)to spectroscopically map galaxies and large-scale structure;(2)an integral field unit(IFU)array of 500 optical fibers and/or a long-slit spectrograph dedicated to fast follow-ups of transient sources for multi-messenger astronomy;(3)a high-resolution spectrometer(R~100000)designed to identify Jupiter analogs and Earth-like planets,with the capability to characterize the atmospheres of hot exoplanets.
基金support provided by the Laboratorio Nacional de Supercómputo del Sureste de México through grant No.O-2016/047。
文摘Using a uniform partitioning of cubic cells,we cover the total volume of aΛCDM cosmological simulation based on particles.We define a visualization cell as a spatial extension of the cubic cell,so that we collect all simulation particles contained in this visualization cell to create a series of Cartesian plots in which the overdensity of matter is clearly visible.We then use these plots as input to a convolutional neural network(CNN)based on the Keras library and TensorFlow for image classification.To assign a class to each plot,we approximate the Hessian of the gravitational potential in the center of the cubic cells.Each selected cubic cell is then assigned a label of 1,2 or 3,depending on the number of positive eigenvalues obtained for the Householder reduction of the Hessian matrix.We apply the CNN to several models,including two models with different visualization volumes,one with a cell size of type L(large)and the other with a cell type S(small).A third model combines the plots of the previous L and S cell types.So far,we have mainly considered a slice parallel to the XY plane to make the plots.The last model is considered based on visualizations of cells that also include slices parallel to the ZX and ZY planes.We find that the accuracy in classification plots is acceptable,and the ability of the models to predict the class works well.These results allow us to demonstrate the aim of this paper,namely that the usual Cartesian plots contain enough information to identify the observed structures of the cosmic web.
基金M.S.thanks DMRC for supportD.S.thanks the compeers of GD Goenka University for continuing assistance.
文摘Gamma-ray bursts(GRBs) are among the brightest objects in the Universe and, hence, can be observed up to a very high redshift. Properly calibrated empirical correlations between intensity and spectral correlations of GRBs can be used to estimate the cosmological parameters. However, the possibility of the evolution of GRBs with redshift is a long-standing puzzle. In this work, we used 162 long-duration GRBs to determine whether GRBs below and above a certain redshift have different properties. The GRBs are split into two groups, and we fit the Amati relation for each group separately. Our findings demonstrate that estimations of the Amati parameters for the two groups are substantially dissimilar. We perform simulations to investigate whether the selection effects could cause the difference. Our analysis shows that the differences may be either intrinsic or due to systematic errors in the data, and the selection effects are not their true origin. However, in-depth analysis with a new data set comprised of 119 long GRBs shows that intrinsic scatter may partly be responsible for such effects.
基金support of the National Key R&D Program of China No. 2022YFF0503404, 2020SKA0110402,MOST-2018YFE0120800,NSFC-11822305, NSFC-11773031,NSFC-11633004, NSFC-11473044, NSFC-11973047the CAS Project for Young Scientists in Basic Research (No. YSBR-092)+1 种基金the Chinese Academy of Sciences grants QYZDJ-SSWSLH017, XDB 23040100, and XDA15020200supported by the science research grants from the China Manned Space Project with NO.CMS-CSST-2021-B01 and CMS-CSST-2021-A01。
文摘A significant excess of the stellar mass density at high redshift has been discovered from the early data release of James Webb Space Telescope(JWST),and it may require a high star formation efficiency.However,this will lead to large number density of ionizing photons in the epoch of reionization(EoR),so that the reionization history will be changed,which can arise tension with the current EoR observations.Warm dark matter(WDM),via the free streaming effect,can suppress the formation of small-scale structure as well as low-mass galaxies.This provides an effective way to decrease the ionizing photons when considering a large star formation efficiency in high-z massive galaxies without altering the cosmic reionization history.On the other hand,the constraints on the properties of WDM can be derived from the JWST observations.In this work,we study WDM as a possible solution to reconcile the JWST stellar mass density of high-z massive galaxies and reionization history.We find that,the JWST high-z comoving cumulative stellar mass density alone has no significant preference for either CDM or WDM model.But using the observational data of other stellar mass density measurements and reionization history,we obtain that the WDM particle mass with mw=0.51_(-0.12)^(+0.22) keV and star formation efficiency parameter f_(*)^(0)> 0.39 in 2σ confidence level can match both the JWST high-z comoving cumulative stellar mass density and the reionization history.
基金supported by the National Key R&D Program of China(2023YFA1607800,2023YFA1607803)the National Natural Science Foundation of China (NSFC,Grant Nos.11925303 and11890691)+3 种基金supported by the National Natural Science Foundation of China (NSFC,Grant No.12203062)by a CAS Project for Young Scientists in Basic Research (No.YSBR-092)supported by science research grants from the China Manned Space Project with No.CMS-CSST-2021-B01supported by the New Cornerstone Science Foundation through the XPLORER prize。
文摘We develop methods to extract key dark energy information from cosmic distance measurements including the BAO scales and supernova(SN) luminosity distances.Demonstrated using simulated data sets of the complete DESI,LSST and Roman surveys designed for BAO and SN distance measurements,we show that using our method,the dynamical behavior of the energy,pressure,equation of state(with its time derivative) of dark energy and the cosmic deceleration function can all be accurately recovered from high-quality data,which allows for robust diagnostic tests for dark energy models.
文摘Three mechanisms for an alternative to the Doppler effect as an explanation for the redshift are reviewed. A fourth mechanism is the attenuation of the light as given by the Beer-Lambert law. The average value of the Hubble constant is therefore derived by processing the galaxies of the NED-D catalog in which the distances are independent of the redshift. The observed anisotropy of the Hubble constant is reproduced by adopting a rim model, a chord model, and both 2D and 3D Voronoi diagrams.
文摘We analyze a simple model for tired light in a cosmological environment, a generalized model, and a spectroscopic model. The three models are tested on different compilations for the distance modulus of supernovae. The tests are negative for the simple tired light and the spectroscopic models, but positive for the generalized tired light model. The percentage error of the distance modulus for the generalized tired light model compared with the distance modulus of standard cosmology is less than one percent over the considered ranges in redshift.
文摘This paper presents the development of a conceptual model of the universe,grounded in the Fine Structure Constant(α≈137.036).The Extended Fine Structure Constant(eFSC)Model exploresαas a function of twin prime mi-croverses(U{137},whereα=137,and U{139},whereα=139),each defined by n-dimensional sets of prime numbers.Property counts for U{137}and U{139}are used in a modified Difference over Sum(DoS)calculation to ap-proximate the fractional component ofα,yielding a Relative Electromagnetic Force(EMF)value ofαII=0.036.Applying this method to additional twin prime pairs produces a distribution of EMF values that reflect the energy pro-files of known Standard Model forces,identifying the strong force as a triad of overlapping EM interactions,and linking the weak force to particle transitions involving neutrons,protons,electrons,and neutrinos.The model provides a conceptual framework for investigating the Higgs mechanism,quantum or-bital structures,quantum entanglement,and potential explanations for grav-ity,dark matter,dark energy,and time dilation.While not intended to supplant any existing physics,the eFSC Model offers a novel,prime-number-based archi-tecture for interpreting the quantum universe through a classical lens.
基金supported by the National Natural Science Foundation of China(Grant Nos.12203012,and 12494575)the Guangxi Natural Science Foundation(Grant No.2023GXNSFBA026114)。
文摘The mass window of ultralight axion dark matter motivated by suppressing the growth of structure on subgalactic scales,m~10-22eV,is now severely constrained by various observation data(e.g.,Lyman-αforest).As an attempt to reopen this mass window,we investigate an alternative ultralight dark matter candidate,the complex scalar field dark matter(SFDM).We derive the relativistic hydrodynamics of the complex SFDM in the framework of cosmological perturbation theory.Our formalism contains two novel ingredients uniquely associated with the complex SFDM model:the Eckart frame defined by the conserved Noether current,and the stiff gauge condition,c_(s)^(2)≡(δP/δρ)|s=1.In the Eckart frame,the complex SFDM is effectively an imperfect fluid with a dissipative energy flux,distinguishing itself from axion dark matter.The energy flux can affect the growth of density fluctuations dynamically.Meanwhile,we apply the stiff gauge condition to find new constitutive equations for the complex SFDM.We revisit the homogeneous evolution of the complex SFDM and present illustrative early-stage solutions for perturbations of the complex SFDM in a simplified setting.We demonstrate the effects of varying the model parameters on the evolution of the perturbation variables.
基金the National SKA Program of China(Grant No.2020SKA0110401)the National Natural Science Foundation of China(Grant No.12033008)K.C.Wong Education Foundation。
文摘We present a GPU-accelerated cosmological simulation code,PhotoNs-GPU,based on an algorithm of Particle Mesh Fast Multipole Method(PM-FMM),and focus on the GPU utilization and optimization.A proper interpolated method for truncated gravity is introduced to speed up the special functions in kernels.We verify the GPU code in mixed precision and different levels of the interpolated method on GPU.A run with single precision is roughly two times faster than double precision for current practical cosmological simulations.But it could induce an unbiased small noise in power spectrum.Compared with the CPU version of PhotoNs and Gadget-2,the efficiency of the new code is significantly improved.Activated all the optimizations on the memory access,kernel functions and concurrency management,the peak performance of our test runs achieves 48%of the theoretical speed and the average performance approaches to~35%on GPU.
