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observational Constraints on Varying Alpha in Λ(α)CDM cosmology

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Communications in Theoretical Physics 2017年第11期67卷 632-640页

作者：韦浩薛冬泽 School of Physics Beijing Institute of Technology

In this work, we consider the so-called Λ(α)CDM cosmology with Λ∝α^(-6) while the fine-structure"constant" α is varying. In this scenario, the accelerated expansion of the universe is driven by the cosmological"constant" Λ(equivalently the vacuum energy), and the varying α is driven by a subdominant scalar field ? coupling with the electromagnetic field. The observational constraints on the varying α and Λ∝α^(-6) models with various couplings BF(?) between the subdominant scalar field ? and the electromagnetic field are considered.

关键词： cosmological constant fine-structure constant observational constraints vacuum energy observational cosmology

Classical cosmology II. The Einstein Ring

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Journal of High Energy Physics, Gravitation and cosmology 2024年第2期10卷 574-598页

作者： Lorenzo Zaninetti Physics Department Turin Italy

The Einstein ring is usually explained in the framework of the gravitational lens. Conversely here we apply the framework of the expansion of a superbubble (SB) in order to explain the spherical appearance of the ring. Two classical equations of motion for SBs are derived in the presence of a linear and a trigonometric decrease for density. A relativistic equation of motion with an inverse square dependence for the density is derived. The angular distance, adopting the minimax approximation, is derived for three relativistic cosmologies: the standard, the flat and the wCDM. We derive the relation between redshift and Euclidean distance, which allows fixing the radius of the Einstein ring. The details of the ring are explained by a simple version of the theory of images.

关键词： cosmology observational cosmology Gravitational Lenses Luminous Arcs

A cosmological model with negative energy photons

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Chinese Physics B 2010年第1期19卷 606-610页

作者：覃一平 Center for Astrophysics Guangzhou University Physics Department Guangxi University

According to recent investigations of states of quantum fields, we postulate that there exist negative energy photons in the universe. With this assumption, we find a solution of Einstein＇s equation without introducing the cosmological constant. A new and sizable type Ia supernovae sample is employed to perform a fit with our model and the conventional model. Both models can well account for the current type Ia supernovae observation and they are not distinguishable. With the new model, the cause of the accelerated expansion of the universe and the mechanism of the negative pressure existing in outer space can be explained in ordinary physical terms.

关键词： relativistic cosmology observational cosmology

The S_(8)tension in light of updated redshift-space distortion data and PAge approximation

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Science China(Physics,Mechanics & Astronomy) 2022年第3期65卷 114-121页

作者： Lu Huang Zhiqi Huang Huan Zhou Zhuoyang Li School of Physics and Astronomy Sun Yat-sen UniversityZhuhai 519082China

One of the most prominent challenges to the standard Lambda cold dark matter(ΛCDM) cosmology is the tension between the structure growth parameter S;constrained by the cosmic microwave background(CMB) data and the smaller one suggested by the cosmic shear data. Recent studies show that, for ΛCDM cosmology, redshift-space distortion(RSD) data also prefers a smaller S;that is ~ 2-3σ lower than the CMB value, but the result is sensitive to the cosmological model. In the present work we update the RSD constraint on S;with the most up-to-date RSD data set where the correlation between data points is properly taken into account. To reduce the model dependence, we add in our Monte Carlo Markov Chain calculation the most up-to-date data sets of Type Ia supernovae(SN) and baryon acoustic oscillations(BAO), whose correlation with RSD is also taken into account, to constrain the background geometry. For ΛCDM cosmology we find S_(8)= 0.812 ± 0.026, which is ~ 2σ larger than previous studies, and hence is consistent with the CMB constraint. By replacing ΛCDM with the parameterization based on cosmic Age(PAge), an almost model-independent description of the late universe, we find that the RSD + SN + BAO constraint on S;is insensitive to the cosmological model.

关键词： observational cosmology large-scale structure of the Universe dark matter

DESI Legacy Imaging Surveys Data Release 9:Cosmological constraints from galaxy clustering and weak lensing using the minimal bias model

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Science China(Physics,Mechanics & Astronomy) 2023年第12期66卷 230-254页

作者： Haojie Xu Hekun Li Jun Zhang Xiaohu Yang Pengjie Zhang Min He Yizhou Gu Jian Qin Zhaozhou Li Antonios Katsianis Ji Yao Zhaoyu Wang Yirong Wang Liping Fu Department of Astronomy Shanghai Jiao Tong UniversityShanghai 200240China Key Laboratory for Particle Astrophysics and cosmology(MOE)/Shanghai Key Laboratory for Particle Physics and cosmology Shanghai 200240China Tsung-Dao Lee Institute Shanghai Jiao Tong UniversityShanghai 201210China CAS Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China Centre for Astrophysics and Planetary Science Racah Institute of PhysicsThe Hebrew UniversityJerusalem 91904Israel Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China Shanghai Key Lab for Astrophysics Shanghai Normal UniversityShanghai 200234China

We present a tentative constraint on cosmological parameters Ω_(m) and σ_(8) from a joint analysis of galaxy clustering and galaxygalaxy lensing from DESI Legacy Imaging Surveys Data Release 9(DR9),covering approximately 10000 square degrees and spanning the redshift range of 0.1 to *** study the dependence of cosmological parameters on lens redshift,we divide lens galaxies into seven approximately volume-limited samples,each with an equal width in photometric *** retrieve the intrinsic projected correlation function w_(p)(r_(p))from the lens samples,we employ a novel method to account for redshift ***,we measured the galaxy-galaxy lensing signal ΔΣ(r_(p))for each lens sample,using source galaxies selected from the shear catalog by applying our Fourier Quad pipeline to DR9 *** model these observables within the flatΛCDM framework,employing the minimal bias *** ensure the reliability of the minimal bias model,we apply conservative scale cuts:r_(p)>8 and 12 h^(-1)Mpc,for w_(p)(r_(p))and ΔΣ(r_(p)),*** findings suggest a mild tendency that S_(8)=σ_(8)√Ω_(m)/0.3increases with lens redshift,although this trend is only marginally *** we combine low redshift samples,the value of S8is determined to be 0.84±0.02,consistent with the Planck results but significantly higher than the 3×2 pt analysis by 2-5σ.Despite the fact that further refinements in measurements and modeling could improve the accuracy of our results,the consistency with standard values demonstrates the potential of our method for more precise and accurate cosmology in the future.

关键词： spatial distribution of galaxies statistical and correlative studies of properties observational cosmology

Investigating the possibility of a turning point in the dark energy equation of state

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Science China(Physics,Mechanics & Astronomy) 2014年第8期57卷 1607-1612页

作者： HU YaZhou LI Miao LI XiaoDong ZHANG ZhenHui State Key Laboratory of Theoretical Physics Institute of Theoretical Physics Chinese Academy of Sciences Kavli Institute for Theoretical Physics China Chinese Academy of Sciences School of Astronomy and Space Science Sun Yat-Sen University Korea Institute for Advanced Study Hoegiro 87Dongdaemun-Gu Seoul 130-722 Korea

We investigate a second order parabolic parametrization, w（a） = wt ＋ wa（at - a）2, which is a direct characterization of a possible turning in w. The cosmological consequence of this parametrization is explored by using the observational data of the SNLS3 type Ia supernovae sample, the CMB measurements from WMAP9 and Planck, the Hubble parameter measurement from HST, and the baryon acoustic oscillation （BAO） measurements from 6dFGS, BOSS DRI 1 and improved WiggleZ. We found the existence of a turning point in w at a - 0.7 is favored at 10- CL. In the epoch 0.55 〈 a 〈 0.9, w 〈 -1 is favored at 10- CL, and this significance increases near a - 0.8, reaching a 20- CL. The parabolic parametrization achieve equivalent performance to the ACDM and Chevallier-Polarski-Linder （CPL） models when the Akaike information criterion was used to assess them. Our analysis shows the value of considering high order parametrizations when studying the cosmological constraints on w.

关键词： dark energy cosmology observational cosmology

f(T) Non-linear Massive Gravity and the Cosmic Acceleration

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Communications in Theoretical Physics 2015年第6期63卷 701-708页

作者：吴悠陈祖成王家昕韦浩 Department of Physics Renmin University of China School of Physics Beijing Institute of Technology Department of Physics Nankai University State Key Laboratory of Theoretical PhysicsInstitute of Theoretical PhysicsChinese Academy of Science

Inspired by the f（R） non-linear massive gravity,we propose a new kind of modified gravity model,namely f（T） non-linear massive gravity,by adding the dRGT mass term reformulated in the vierbein formalism,to the f（T）*** then investigate the cosmological evolution of f（T） massive gravity,and constrain it by using the latest observational *** find that it slightly favors a crossing of the phantom divide line from the quintessence-like phase(ω;>-1) to the phantom-like one(ω;<-1) as redshift decreases.

关键词： massive gravity f(T)theory modified gravity dark energy observational cosmology

Method of determining cosmological parameter ranges with samples of candles with an intrinsic distribution

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Chinese Physics B 2006年第7期15卷 1645-1652页

作者：覃一平张彬彬董云明张富文李怀珍贾兰伟毛李胜陆睿静易庭丰崔晓红张志彬 National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Physics Department Guangxi University Nanning Guangxi 530004 China The Graduate School of the Chinese Academy of Sciences Beijing 100049 China

In this paper, the effect of the intrinsic distribution of cosmological candles is investigated. We find that in the case of a narrow distribution the deviation of the observed modulus of sources from the expected central value can be estimated within a ceratin range. We thus introduce lower and upper limits of X^2, X^2min and X^2max to estimate cosmological parameters by applying the conventional minimizing X^2 method. We apply this method to a gammaray burst （GRB） sample as well as to a combined sample including this GRB sample and an SN Ia sample. Our analysis shows that： a） in the case of assuming an intrinsic distribution of candles of the GRB sample, the effect of the distribution is obvious and should not be neglected; b） taking into account this effect would lead to a poorer constraint of the cosmological parameter ranges. The analysis suggests that in the attempt of constraining the cosmological model with current GRB samples, the results tend to be worse than was previously anticipated if the mentioned intrinsic distribution does exist.

关键词： cosmological parameters observational cosmology distance scale

Expanding or Static Universe: Emergence of a New Paradigm

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International Journal of Astronomy and Astrophysics 2021年第2期11卷 190-231页

作者： Paul A. LaViolette The Starburst Foundation Niskayuna NY USA

The no-evolution, concordance expanding universe cosmology and no-evolution, static universe tired light model are compared against observational data on eight cosmology tests. The no-evolution tired light model is found to make a superior fit on all tests. Any attempts to introduce evolutionary corrections to improve the concordance cosmology fit on one test often worsen its fit on other tests. Light curve data of high redshift gamma ray bursts and quasars fail to support claims for cosmological time dilation due to expansion. Also, the SCP supernova light curve test results are considered to be flawed by selection effect biases. The big bang theory also has difficulty accounting for redshift quantization, for the multi-megaparsec periodicity seen in the distribution of galaxy superclusters, and for the discovery of galaxies at redshifts as high as z ~11.9. In overview, it is concluded that a static universe cosmology must be sought to explain the origin of the universe. One possible choice is a cosmology that predicts nonconservative tired-light redshifting in intergalactic space, the continuous creation of neutrons in space, the rate of matter creation scaling with both celestial body mass and temperature, galaxies growing progressively in size, and changing their morphology in the manner suggested by Jeans and Hubble.

关键词： Cosmological Redshift Tired Light Effect Hubble Constant Galactic Evolution Continuous Creation Subatomic Particles Reaction-Diffusion Systems Open Systems Self-Organizing Systems observational cosmology Tolman Test Angular-Size-Redshift Test Hubble Diagram Supernovae