5D World-Universe Model is based on the decisive role of the Medium of the World composed of massive particles: protons, electrons, photons, neutrinos, and dark matter particles. In this manuscript we discuss differen...5D World-Universe Model is based on the decisive role of the Medium of the World composed of massive particles: protons, electrons, photons, neutrinos, and dark matter particles. In this manuscript we discuss different aspects of the gravitation: measured values of the Newtonian parameter of Gravitation and different Gravitational effects (gravitational lensing, cosmological redshift, gravitational deflection of light and gravitational refraction, proposed in the present paper). We show inter-connectivity of all cosmological parameters and provide a mathematical framework that allows direct calculation of them based on the value of the gravitational parameter. We analyze the difference between Electromagnetism and Gravitoelectromagnetism and make a conclusion about the mandatory existence of the Medium of the World. This paper aligns the World-Universe Model with the Le Sage’s theory of gravitation and makes a deduction on Gravity, Space and Time be emergent phenomena.展开更多
Modern cosmological theory is based on the Friedmann-Robertson-Walker （FRW） metric. Often written in terms of co-moving coordinates, this well-known solution to Einstein＇s equations owes its elegant and highly prac...Modern cosmological theory is based on the Friedmann-Robertson-Walker （FRW） metric. Often written in terms of co-moving coordinates, this well-known solution to Einstein＇s equations owes its elegant and highly practical formulation to the cosmological principle and Weyl＇s postulate, upon which it is founded. However, there is physics behind such symmetries, and not all of it has yet been recognized. In this paper, we derive the FRW metric coefficients from the general form of the spherically symmetric line element and demonstrate that, because the co-moving frame also happens to be in free fall, the symmetries in FRW are valid only for a medium with zero active mass. In other words, the spacetime of a perfect fluid in cosmology may be correctly written as FRW only when its equation of state is p ＋ 3p = 0, in terms of the total pressure p and total energy density p. There is now compelling observational support for this conclusion, including the Alcock-Paczyriski test, which shows that only an FRW cosmology with zero active mass is consistent with the latest model-independent baryon acoustic oscillation data.展开更多
In this work, a computer optimization model has been developed that allows one to load the initial data of observations of supernovae 1a into a table and, in simple steps, by searching for the best fit between observa...In this work, a computer optimization model has been developed that allows one to load the initial data of observations of supernovae 1a into a table and, in simple steps, by searching for the best fit between observations and theory, obtain the values of the parameters of cosmological models. The optimization is carried out assuming that the absolute magnitude of supernovae is not constant, but evolves with time. It is assumed that the dependence of the absolute magnitude on the redshift is linear: M = M( z = 0) + ε<sub>c </sub>z, where ε<sub>c</sub> is the evolution coefficient of the absolute magnitude of type 1a supernovae. In the case of a flat universe ( Ω<sub>M</sub> + Ω<sub>Λ</sub> = 1 ), the best fit between theory and observation is εc </sub>= 0.304. In this case, for the cosmological parameters we obtain Ω<sub>Λ</sub> = 0.000, Ω<sub>M</sub><sub></sub> =1.000. Naturally, this result exactly coincides with the simulation result for the model with zero cosmological constant ( εc</sub> = 0.304, q<sub>0</sub> = 0.500 ). Within the framework of the ΛCDM model, without restriction on space curvature ( Ω<sub>M</sub> + Ω<sub>Λ</sub>+ Ω<sub>K</sub><sub></sub> = 1 ), we obtain the following values: εc</sub> </sub>= 0.304, ΩΛ</sub> = 0.000, ΩM </sub>= 1.000, Ω<sub>K</sub></sub></sub></sub> =0.000. Those, this case also leads to a flat model of the Universe ( Ω<sub>K</sub><sub></sub></sub></sub> =0.000 ). In this work, the critical influence of the absolute magnitude M of type 1a supernovae on the cosmological parameters is also shown. In particular, it was found that a change in this value by only 0.4<sup>m </sup>(from -19.11 to -18.71) leads to a change in the parameters from ΩΛ</sub> = 0.7 and ΩM</sub></sub> = 0.3 to ΩΛ</sub> = 0 and ΩM</sub> =1.展开更多
The Bianchi type- III and Kantowski-Sachs (KS) Universes filled with dark energy from a wet dark fluid has been considered. A new equation of state for the dark energy component of the universe has been used. It is mo...The Bianchi type- III and Kantowski-Sachs (KS) Universes filled with dark energy from a wet dark fluid has been considered. A new equation of state for the dark energy component of the universe has been used. It is modeled on the equation of state ρ=γ(ρ -ρ *) , which can describe a liquid, for example water. The exact solutions to the corresponding field equations are obtained in quadrature form. The solution for constant deceleration parameter have been studied in detail for power-law and exponential forms both. The case γ = 0,γ =1,and γ =1/3have been also analysed.展开更多
A theory of（4＋1）-dimensional gravity has been developed on the basis of which equivalent to the theory of general relativity by teleparallel.The fundamental gravitational field variables are the 5-dimensional（5D）...A theory of（4＋1）-dimensional gravity has been developed on the basis of which equivalent to the theory of general relativity by teleparallel.The fundamental gravitational field variables are the 5-dimensional（5D） vector fields（pentad）,defined globally on a manifold M,and gravity is attributed to the torsion.The Lagrangian density is quadratic in the torsion tensor.We then apply the field equations to two different homogenous and isotropic geometric structures which give the same line element,i.e.,FRW in five dimensions.The cosmological parameters are calculated and some cosmological problems are discussed.展开更多
Cosmological Models frequently suggest the existence of physical, quantities, e.g. dark energy, we cannot yet observe and measure directly. Their values are obtained indirectly setting them equal to values and accurac...Cosmological Models frequently suggest the existence of physical, quantities, e.g. dark energy, we cannot yet observe and measure directly. Their values are obtained indirectly setting them equal to values and accuracy of the associated model parameters which best fit model and observation. Apparently results are so accurate that some researchers speak of precision cosmology. The accuracy attributed to these indirect values of the physical quantities however does not include the uncertainty of the model used to get them. We suggest a Confidence Level Estimator to be attached to these indirect measurements and apply it to current cosmological models.展开更多
The Bianchi type- VIo universe filled with dark energy from a wet dark fluid has been considered. A new equation of state for the dark energy component of the universe has been used. It is modeled on the equation of s...The Bianchi type- VIo universe filled with dark energy from a wet dark fluid has been considered. A new equation of state for the dark energy component of the universe has been used. It is modeled on the equation of state p=γ(ρ-ρ﹡) which can describe a liquid, for example water. The exact solutions to the corresponding field equations are obtained in quadrature form. The solution for constant deceleration parameter have been studied in detail for power-law and exponential forms both. The case γ=0, γ=1, and γ=1/3 have been also analysed.展开更多
In this paper, we have studied the generalized chaplygin gas of interacting dark energy to ob-tain the equation of state for the generalized chaplygin gas energy density in anisotropic Bianchi type-I cosmological mode...In this paper, we have studied the generalized chaplygin gas of interacting dark energy to ob-tain the equation of state for the generalized chaplygin gas energy density in anisotropic Bianchi type-I cosmological model. For negative value of B in equation of state of generalized chaplygin gas, we see that γ effΛ<-1 , that corresponds to a universe dominated by phantom dark energy.展开更多
We hypothesize that the quantum realm and the cosmos are linked by a scaling relation where the gravitational coupling constant <i>α<sub>G</sub></i> is the scale factor and decreases with cosm...We hypothesize that the quantum realm and the cosmos are linked by a scaling relation where the gravitational coupling constant <i>α<sub>G</sub></i> is the scale factor and decreases with cosmic time. We propose a simple cosmological model where cosmic inflation, dark energy and dark matter could be redundant concepts. We show that cosmological parameters such as the Hubble constant, the age, density and mass of the observable Universe could be derived simply from quantum parameters. Finally, we propose a fundamental MOND formula with no interpolating function and an acceleration parameter simply derived from the Hubble constant.展开更多
We analyse the possibility that the observed cosmological redshift may be cumulatively due to the expansion of the universe and the tired light phenomenon. Since the source of both the redshifts is the same, they both...We analyse the possibility that the observed cosmological redshift may be cumulatively due to the expansion of the universe and the tired light phenomenon. Since the source of both the redshifts is the same, they both independently relate to the same proper distance of the light source. Using this approach we have developed a hybrid model combining the Einstein de Sitter model and the tired light model that yields a slightly better fit to Supernovae Ia redshift data using one parameter than the standard ΛCDM model with two parameters. We have shown that the ratio of tired light component to the Einstein de Sitter component of redshift has evolved from 2.5 in the past, corresponding to redshift 1000, to its present value of 1.5. The hybrid model yields Hubble constant H0 =69.11(±0.53)km·s-1 ·Mpc-1 and the deceleration parameter q0 =-0.4. The component of Hubble constant responsible for expansion of the universe is 40% of H0 and for the tired light is 60% of H0. Consequently, the critical density is only 16% of its currently accepted value;a lot less dark matter is needed to make up the critical density. In addition, the best data fit yields the cosmological constant density parameter =0. The tired light effect may thus be considered equivalent to the cosmological constant in the hybrid model.展开更多
In this work, we compare the impacts given by χ^2 statistics and Bayesian statistics. Bayesian statistics is a new statistical method proposed by [C. Ma, P. S. Corasaniti, and B. A. Bassett, arXiv:1603.08519[astro-ph...In this work, we compare the impacts given by χ^2 statistics and Bayesian statistics. Bayesian statistics is a new statistical method proposed by [C. Ma, P. S. Corasaniti, and B. A. Bassett, arXiv:1603.08519[astro-ph.CO](2016)]recently, which gives a fully account for the standard-candle parameter dependence of the data covariance matrix. For this two statistical methods, we explore the possible redshift-dependence of stretch-luminosity parameter α and colorluminosity parameter β by using redshift tomography. By constraining the ΛCDM model, we check the consistency of cosmology-fit results given by the SN sample of each redshift bin. We also adopt the linear parametrization to explore the possible evolution of α and β and the deceleration parameter q(z) for CPL, JBP, BA and Wang models. We find that:(i) Using the full JLA data, at high redshift α has a trend of decreasing at more than 1.5σ confidence level(CL),and β has a significant trend of decreasing at more than 19σ CL.(ii) Compared with χ^2 statistics(constant α, β) and Bayesian statistics(constant α, β), Bayesian statistics(linear α and β) yields a larger best-fit value of fractional matter density ?m0 from JLA+CMB+GC data, which is much closer to slightly deviates from the best-fit result given by other cosmological observations.(iii) The figure of merit(FoM) given by JLA+CMB+GC data from Bayesian statistics is also larger than the FoM from χ^2 statistics, which indicates that former statistics has a better accuracy.(iv) q(z) given by both statistical methods favor an eternal cosmic acceleration at 1σ CL.展开更多
We constrain the Cardassian expansion models from the latest observa- tions, including the updated Gamma-ray bursts （GRBs）, which are calibrated using a cosmology independent method from the Union2 compilation of ty...We constrain the Cardassian expansion models from the latest observa- tions, including the updated Gamma-ray bursts （GRBs）, which are calibrated using a cosmology independent method from the Union2 compilation of type Ia supernovae （SNe Ia）. By combining the GRB data with the joint observations from the Union2 SNe Ia set, along with the results from the Cosmic Microwave Background radia- tion observation from the seven-year Wilkinson Microwave Anisotropy Probe and the baryonic acoustic oscillation observation galaxy sample from the spectroscopic Sloan Digital Sky Survey Data Release. we find significant constraints on the model oarameters of the original Cardassian model ΩM0=0.282-0.014^0.015,n=0.03-0.05^＋0.05 and n=-0.16-3.26^＋0.25,β=0.76-0.58^＋0.34 of the modified polytropic Cardassian model, which are consistent with the ACDM model in a l-or confidence region. From the reconstruction of the deceleration parameter q（z） in Cardassian models, we obtain the transition redshift ZT = 0.73 ± 0.04 for the original Cardassian model and ZT = 0.68 ± 0.04 for the modified polytropic Cardassian model.展开更多
From Baryon Acoustic Oscillation measurements with Sloan Digital Sky Survey SDSS DR14 galaxies, and the acoustic horizon angle measured by the Planck Collaboration, we obtain Ωm=0.2724±0.0047, and h+0.020&sd...From Baryon Acoustic Oscillation measurements with Sloan Digital Sky Survey SDSS DR14 galaxies, and the acoustic horizon angle measured by the Planck Collaboration, we obtain Ωm=0.2724±0.0047, and h+0.020⋅∑mv=0.7038±0.0060, assuming flat space and a cosmological constant. We combine this result with the 2018 Planck “TT, TE, EE + lowE + lensing” analysis, and update a study of ∑mv with new direct measurements of σ8, and obtain ∑mv=0.27±0.08 eV assuming three nearly degenerate neutrino eigenstates. Measurements are consistent with Ωk=0, and Ωde(a)=ΩΛ constant.展开更多
We investigate direction dependence and non-Gaussian features in high-z cosmological data using ?_(χ~2) and ?_χ statistics and the Kolmogorov-Smirnov test. These techniques are applied on a set of calibrated long ga...We investigate direction dependence and non-Gaussian features in high-z cosmological data using ?_(χ~2) and ?_χ statistics and the Kolmogorov-Smirnov test. These techniques are applied on a set of calibrated long gamma-ray bursts(GRBs) and its combination with recent Type Ia supernovae data(Union2). Our statistical analysis shows a weak but consistent direction dependence in both the data sets.The analysis also indicates a non-Gaussian nature of errors in both data sets.展开更多
We present a study of spectrum estimation of relic gravitational waves(RGWs) as a Gaussian stochastic background from output signals of future space-borne interferometers, like LISA and ASTROD.As the target of detecti...We present a study of spectrum estimation of relic gravitational waves(RGWs) as a Gaussian stochastic background from output signals of future space-borne interferometers, like LISA and ASTROD.As the target of detection, the analytical spectrum of RGWs generated during inflation is described by three parameters: the tensor-scalar ratio, the spectral index and the running index. The Michelson interferometer is shown to have a better sensitivity than Sagnac and symmetrized Sagnac. For RGW detection, we analyze the auto-correlated signals for a single interferometer, and the cross-correlated, integrated as well as unintegrated signals for a pair of interferometers, and give the signal-to-noise ratio(SNR) for RGW, and obtain lower limits of the RGW parameters that can be detected. By suppressing noise level, a pair has a sensitivity2 orders better than a single for one year observation. SNR of LISA will be 4–5 orders higher than that of Advanced LIGO for the default RGW. To estimate the spectrum, we adopt the maximum likelihood(ML)estimation, calculate the mean and covariance of signals, obtain the Gaussian probability density function(PDF) and the likelihood function, and derive expressions for the Fisher matrix and the equation of the ML estimate for the spectrum. The Newton-Raphson method is used to solve the equation by iteration. When the noise is dominantly large, a single LISA is not effective for estimating the RGW spectrum as the actual noise in signals is not known accurately. For cross-correlating a pair, the spectrum cannot be estimated from the integrated output signals either, and only one parameter can be estimated with the other two being either fixed or marginalized. We use the ensemble averaging method to estimate the RGW spectrum from the un-integrated output signals. We also adopt a correlation of un-integrated signals to estimate the spectrum and three parameters of RGW in a Bayesian approach. For all three methods, we provide simulations to illustrate their feasibility.展开更多
In this work, we explore the cosmological implications of different baryon acoustic oscillation （BAO） data, including the BAO data extracted by using the spherically averaged one-dimensional galaxy clustering （GC）...In this work, we explore the cosmological implications of different baryon acoustic oscillation （BAO） data, including the BAO data extracted by using the spherically averaged one-dimensional galaxy clustering （GC） statistics （hereafter BAO 1） and the BAO data obtained by using the anisotropic two-dimensional GC statistics （hereafter BAO2）. To make a comparison, we also take into account the case without BAO data （hereafter NO BAO）. Firstly, making use of these BAO data, as well as the SNLS3 type la supernovae sample and the Planck distance priors data, we give the cosmological constraints of the ACDM, the wCDM, and the Chevallier-Polarski-Linder （CPL） model. Then, we discuss the impacts of different BAO data on cosmological consquences, including its effects on parameter space, equation of state （EoS）, figure of merit （FoM）, deceleration-acceleration transition redshift, Hubble parameter H（z）, deceleration parameter q（z）, statefinder hierarchy S3^（1）（z）, S4^（1）（z） and cosmic age t（z）. We find that： （1） NO BAO data always give a smallest fractional matter density Ωm0, a largest fractional curvature density Ωk0 and a largest Hubble constant h; in contrast, BAO1 data always give a largest Ωm0, a smallest Ωk0 and a smallest h. （2） For the wCDM and the CPL model, NO BAO data always give a largest EoS w; in contrast, BA02 data always give a smallest w. （3） Compared with the case of BAO1, BAO2 data always give a slightly larger FoM, and thus can give a cosmological constraint with a slightly better accuracy. （4） The impacts of different BAO data on the cosmic evolution and the comic age are very small, and cannot be distinguished by using various dark energy diagnoses and the cosmic age data.展开更多
We constrain three cosmological models - the concordance cold dark matter plus cosmological constant（ΛCDM） model, the power-law（PL） model, and the Rh =ct model - using the available local probes, which include th...We constrain three cosmological models - the concordance cold dark matter plus cosmological constant（ΛCDM） model, the power-law（PL） model, and the Rh =ct model - using the available local probes, which include the JLA compilation of type-Ia supernovae（SNe Ia）, the direct measurement of the Hubble constant（Hz）, and the baryon acoustic oscillations（BAO）. For the ΛCDM model, we consider two different cases, i.e. zero and non-zero spatial curvature. We find that by using the JLA alone, the ΛCDM and PL models are indistinguishable, but the Rh =ct model is strongly disfavored. If we combine JLA＋Hz, the ΛCDM model is strongly favored over the other two models. The combination of all three datasets supports ΛCDM as the best model. We also use the low-redshift（z 〈0.2） data to constrain the deceleration parameter using the cosmography method, and find that only the ΛCDM model is consistent with cosmography. However, there is no strong evidence to distinguish between flat and non-flatΛCDM models by using the local data alone.展开更多
We investigate the constraints on a generalized Chaplygin gas （GCG） model using the gold sample type-Ia supernovae （She Ia） data, the new Supernova Legacy Survey （SNLS） Sne Ia data and the size of baryonic acous...We investigate the constraints on a generalized Chaplygin gas （GCG） model using the gold sample type-Ia supernovae （She Ia） data, the new Supernova Legacy Survey （SNLS） Sne Ia data and the size of baryonic acoustic oscillation peak found in Sloan Digital Sky Survey （SDSS）. In a spatially flat universe case we obtain, at a 95.4% confidence level, A8 = 0.76^＋0.07 -0.07 and α= 0.028^＋0.322 -0.2382 Our results are consistent with the ACDM model （α= 0）, but rule out the standard Chaplygin gas model （α= 1）.展开更多
Non-static inhomogeneous cosmological models are obtained in general relativity for the case of a plane symmetric massless scalar field with cosmological constant A, when the source of the gravitational field is a vis...Non-static inhomogeneous cosmological models are obtained in general relativity for the case of a plane symmetric massless scalar field with cosmological constant A, when the source of the gravitational field is a viscous fluid. Some physical and geometrical behaviors of the solutions are also discussed.展开更多
文摘5D World-Universe Model is based on the decisive role of the Medium of the World composed of massive particles: protons, electrons, photons, neutrinos, and dark matter particles. In this manuscript we discuss different aspects of the gravitation: measured values of the Newtonian parameter of Gravitation and different Gravitational effects (gravitational lensing, cosmological redshift, gravitational deflection of light and gravitational refraction, proposed in the present paper). We show inter-connectivity of all cosmological parameters and provide a mathematical framework that allows direct calculation of them based on the value of the gravitational parameter. We analyze the difference between Electromagnetism and Gravitoelectromagnetism and make a conclusion about the mandatory existence of the Medium of the World. This paper aligns the World-Universe Model with the Le Sage’s theory of gravitation and makes a deduction on Gravity, Space and Time be emergent phenomena.
文摘Modern cosmological theory is based on the Friedmann-Robertson-Walker （FRW） metric. Often written in terms of co-moving coordinates, this well-known solution to Einstein＇s equations owes its elegant and highly practical formulation to the cosmological principle and Weyl＇s postulate, upon which it is founded. However, there is physics behind such symmetries, and not all of it has yet been recognized. In this paper, we derive the FRW metric coefficients from the general form of the spherically symmetric line element and demonstrate that, because the co-moving frame also happens to be in free fall, the symmetries in FRW are valid only for a medium with zero active mass. In other words, the spacetime of a perfect fluid in cosmology may be correctly written as FRW only when its equation of state is p ＋ 3p = 0, in terms of the total pressure p and total energy density p. There is now compelling observational support for this conclusion, including the Alcock-Paczyriski test, which shows that only an FRW cosmology with zero active mass is consistent with the latest model-independent baryon acoustic oscillation data.
文摘In this work, a computer optimization model has been developed that allows one to load the initial data of observations of supernovae 1a into a table and, in simple steps, by searching for the best fit between observations and theory, obtain the values of the parameters of cosmological models. The optimization is carried out assuming that the absolute magnitude of supernovae is not constant, but evolves with time. It is assumed that the dependence of the absolute magnitude on the redshift is linear: M = M( z = 0) + ε<sub>c </sub>z, where ε<sub>c</sub> is the evolution coefficient of the absolute magnitude of type 1a supernovae. In the case of a flat universe ( Ω<sub>M</sub> + Ω<sub>Λ</sub> = 1 ), the best fit between theory and observation is εc </sub>= 0.304. In this case, for the cosmological parameters we obtain Ω<sub>Λ</sub> = 0.000, Ω<sub>M</sub><sub></sub> =1.000. Naturally, this result exactly coincides with the simulation result for the model with zero cosmological constant ( εc</sub> = 0.304, q<sub>0</sub> = 0.500 ). Within the framework of the ΛCDM model, without restriction on space curvature ( Ω<sub>M</sub> + Ω<sub>Λ</sub>+ Ω<sub>K</sub><sub></sub> = 1 ), we obtain the following values: εc</sub> </sub>= 0.304, ΩΛ</sub> = 0.000, ΩM </sub>= 1.000, Ω<sub>K</sub></sub></sub></sub> =0.000. Those, this case also leads to a flat model of the Universe ( Ω<sub>K</sub><sub></sub></sub></sub> =0.000 ). In this work, the critical influence of the absolute magnitude M of type 1a supernovae on the cosmological parameters is also shown. In particular, it was found that a change in this value by only 0.4<sup>m </sup>(from -19.11 to -18.71) leads to a change in the parameters from ΩΛ</sub> = 0.7 and ΩM</sub></sub> = 0.3 to ΩΛ</sub> = 0 and ΩM</sub> =1.
文摘The Bianchi type- III and Kantowski-Sachs (KS) Universes filled with dark energy from a wet dark fluid has been considered. A new equation of state for the dark energy component of the universe has been used. It is modeled on the equation of state ρ=γ(ρ -ρ *) , which can describe a liquid, for example water. The exact solutions to the corresponding field equations are obtained in quadrature form. The solution for constant deceleration parameter have been studied in detail for power-law and exponential forms both. The case γ = 0,γ =1,and γ =1/3have been also analysed.
文摘A theory of（4＋1）-dimensional gravity has been developed on the basis of which equivalent to the theory of general relativity by teleparallel.The fundamental gravitational field variables are the 5-dimensional（5D） vector fields（pentad）,defined globally on a manifold M,and gravity is attributed to the torsion.The Lagrangian density is quadratic in the torsion tensor.We then apply the field equations to two different homogenous and isotropic geometric structures which give the same line element,i.e.,FRW in five dimensions.The cosmological parameters are calculated and some cosmological problems are discussed.
文摘Cosmological Models frequently suggest the existence of physical, quantities, e.g. dark energy, we cannot yet observe and measure directly. Their values are obtained indirectly setting them equal to values and accuracy of the associated model parameters which best fit model and observation. Apparently results are so accurate that some researchers speak of precision cosmology. The accuracy attributed to these indirect values of the physical quantities however does not include the uncertainty of the model used to get them. We suggest a Confidence Level Estimator to be attached to these indirect measurements and apply it to current cosmological models.
文摘The Bianchi type- VIo universe filled with dark energy from a wet dark fluid has been considered. A new equation of state for the dark energy component of the universe has been used. It is modeled on the equation of state p=γ(ρ-ρ﹡) which can describe a liquid, for example water. The exact solutions to the corresponding field equations are obtained in quadrature form. The solution for constant deceleration parameter have been studied in detail for power-law and exponential forms both. The case γ=0, γ=1, and γ=1/3 have been also analysed.
文摘In this paper, we have studied the generalized chaplygin gas of interacting dark energy to ob-tain the equation of state for the generalized chaplygin gas energy density in anisotropic Bianchi type-I cosmological model. For negative value of B in equation of state of generalized chaplygin gas, we see that γ effΛ<-1 , that corresponds to a universe dominated by phantom dark energy.
文摘We hypothesize that the quantum realm and the cosmos are linked by a scaling relation where the gravitational coupling constant <i>α<sub>G</sub></i> is the scale factor and decreases with cosmic time. We propose a simple cosmological model where cosmic inflation, dark energy and dark matter could be redundant concepts. We show that cosmological parameters such as the Hubble constant, the age, density and mass of the observable Universe could be derived simply from quantum parameters. Finally, we propose a fundamental MOND formula with no interpolating function and an acceleration parameter simply derived from the Hubble constant.
文摘We analyse the possibility that the observed cosmological redshift may be cumulatively due to the expansion of the universe and the tired light phenomenon. Since the source of both the redshifts is the same, they both independently relate to the same proper distance of the light source. Using this approach we have developed a hybrid model combining the Einstein de Sitter model and the tired light model that yields a slightly better fit to Supernovae Ia redshift data using one parameter than the standard ΛCDM model with two parameters. We have shown that the ratio of tired light component to the Einstein de Sitter component of redshift has evolved from 2.5 in the past, corresponding to redshift 1000, to its present value of 1.5. The hybrid model yields Hubble constant H0 =69.11(±0.53)km·s-1 ·Mpc-1 and the deceleration parameter q0 =-0.4. The component of Hubble constant responsible for expansion of the universe is 40% of H0 and for the tired light is 60% of H0. Consequently, the critical density is only 16% of its currently accepted value;a lot less dark matter is needed to make up the critical density. In addition, the best data fit yields the cosmological constant density parameter =0. The tired light effect may thus be considered equivalent to the cosmological constant in the hybrid model.
文摘In this work, we compare the impacts given by χ^2 statistics and Bayesian statistics. Bayesian statistics is a new statistical method proposed by [C. Ma, P. S. Corasaniti, and B. A. Bassett, arXiv:1603.08519[astro-ph.CO](2016)]recently, which gives a fully account for the standard-candle parameter dependence of the data covariance matrix. For this two statistical methods, we explore the possible redshift-dependence of stretch-luminosity parameter α and colorluminosity parameter β by using redshift tomography. By constraining the ΛCDM model, we check the consistency of cosmology-fit results given by the SN sample of each redshift bin. We also adopt the linear parametrization to explore the possible evolution of α and β and the deceleration parameter q(z) for CPL, JBP, BA and Wang models. We find that:(i) Using the full JLA data, at high redshift α has a trend of decreasing at more than 1.5σ confidence level(CL),and β has a significant trend of decreasing at more than 19σ CL.(ii) Compared with χ^2 statistics(constant α, β) and Bayesian statistics(constant α, β), Bayesian statistics(linear α and β) yields a larger best-fit value of fractional matter density ?m0 from JLA+CMB+GC data, which is much closer to slightly deviates from the best-fit result given by other cosmological observations.(iii) The figure of merit(FoM) given by JLA+CMB+GC data from Bayesian statistics is also larger than the FoM from χ^2 statistics, which indicates that former statistics has a better accuracy.(iv) q(z) given by both statistical methods favor an eternal cosmic acceleration at 1σ CL.
基金supported by the National Science Foundation of China underthe Distinguished Young Scholar (Grant No. 10825313)the Key Project (Grant No. 10533010)+4 种基金the National Basic Research Program of China (973 ProgramGrant No. 2007CB815401)support by the National Natural Science Foundation of China (GrantNo. 10705055)the Foundation for the Author of National Excellent Doctoral Dissertation of China(Grant No. 200922)the Century Educational Talents Plan of Chinese Education Ministry (GrantNo. 09-0144)
文摘We constrain the Cardassian expansion models from the latest observa- tions, including the updated Gamma-ray bursts （GRBs）, which are calibrated using a cosmology independent method from the Union2 compilation of type Ia supernovae （SNe Ia）. By combining the GRB data with the joint observations from the Union2 SNe Ia set, along with the results from the Cosmic Microwave Background radia- tion observation from the seven-year Wilkinson Microwave Anisotropy Probe and the baryonic acoustic oscillation observation galaxy sample from the spectroscopic Sloan Digital Sky Survey Data Release. we find significant constraints on the model oarameters of the original Cardassian model ΩM0=0.282-0.014^0.015,n=0.03-0.05^＋0.05 and n=-0.16-3.26^＋0.25,β=0.76-0.58^＋0.34 of the modified polytropic Cardassian model, which are consistent with the ACDM model in a l-or confidence region. From the reconstruction of the deceleration parameter q（z） in Cardassian models, we obtain the transition redshift ZT = 0.73 ± 0.04 for the original Cardassian model and ZT = 0.68 ± 0.04 for the modified polytropic Cardassian model.
文摘From Baryon Acoustic Oscillation measurements with Sloan Digital Sky Survey SDSS DR14 galaxies, and the acoustic horizon angle measured by the Planck Collaboration, we obtain Ωm=0.2724±0.0047, and h+0.020⋅∑mv=0.7038±0.0060, assuming flat space and a cosmological constant. We combine this result with the 2018 Planck “TT, TE, EE + lowE + lensing” analysis, and update a study of ∑mv with new direct measurements of σ8, and obtain ∑mv=0.27±0.08 eV assuming three nearly degenerate neutrino eigenstates. Measurements are consistent with Ωk=0, and Ωde(a)=ΩΛ constant.
文摘We investigate direction dependence and non-Gaussian features in high-z cosmological data using ?_(χ~2) and ?_χ statistics and the Kolmogorov-Smirnov test. These techniques are applied on a set of calibrated long gamma-ray bursts(GRBs) and its combination with recent Type Ia supernovae data(Union2). Our statistical analysis shows a weak but consistent direction dependence in both the data sets.The analysis also indicates a non-Gaussian nature of errors in both data sets.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11421303, 11675165 and 11633001)SRFDP+1 种基金CASthe Strategic Priority Research Program "The Emergence of Cosmological Structures" of the Chinese Academy of Sciences (Grant No. XDB09000000)
文摘We present a study of spectrum estimation of relic gravitational waves(RGWs) as a Gaussian stochastic background from output signals of future space-borne interferometers, like LISA and ASTROD.As the target of detection, the analytical spectrum of RGWs generated during inflation is described by three parameters: the tensor-scalar ratio, the spectral index and the running index. The Michelson interferometer is shown to have a better sensitivity than Sagnac and symmetrized Sagnac. For RGW detection, we analyze the auto-correlated signals for a single interferometer, and the cross-correlated, integrated as well as unintegrated signals for a pair of interferometers, and give the signal-to-noise ratio(SNR) for RGW, and obtain lower limits of the RGW parameters that can be detected. By suppressing noise level, a pair has a sensitivity2 orders better than a single for one year observation. SNR of LISA will be 4–5 orders higher than that of Advanced LIGO for the default RGW. To estimate the spectrum, we adopt the maximum likelihood(ML)estimation, calculate the mean and covariance of signals, obtain the Gaussian probability density function(PDF) and the likelihood function, and derive expressions for the Fisher matrix and the equation of the ML estimate for the spectrum. The Newton-Raphson method is used to solve the equation by iteration. When the noise is dominantly large, a single LISA is not effective for estimating the RGW spectrum as the actual noise in signals is not known accurately. For cross-correlating a pair, the spectrum cannot be estimated from the integrated output signals either, and only one parameter can be estimated with the other two being either fixed or marginalized. We use the ensemble averaging method to estimate the RGW spectrum from the un-integrated output signals. We also adopt a correlation of un-integrated signals to estimate the spectrum and three parameters of RGW in a Bayesian approach. For all three methods, we provide simulations to illustrate their feasibility.
基金supported by the National Natural Science Foundation of China(Grant Nos.11405024,11275247,and 11335012)the Fundamental Research Funds for the Central Universities(Grant No.16lgpy50)a985 grant at Sun Yat-Sen University
文摘In this work, we explore the cosmological implications of different baryon acoustic oscillation （BAO） data, including the BAO data extracted by using the spherically averaged one-dimensional galaxy clustering （GC） statistics （hereafter BAO 1） and the BAO data obtained by using the anisotropic two-dimensional GC statistics （hereafter BAO2）. To make a comparison, we also take into account the case without BAO data （hereafter NO BAO）. Firstly, making use of these BAO data, as well as the SNLS3 type la supernovae sample and the Planck distance priors data, we give the cosmological constraints of the ACDM, the wCDM, and the Chevallier-Polarski-Linder （CPL） model. Then, we discuss the impacts of different BAO data on cosmological consquences, including its effects on parameter space, equation of state （EoS）, figure of merit （FoM）, deceleration-acceleration transition redshift, Hubble parameter H（z）, deceleration parameter q（z）, statefinder hierarchy S3^（1）（z）, S4^（1）（z） and cosmic age t（z）. We find that： （1） NO BAO data always give a smallest fractional matter density Ωm0, a largest fractional curvature density Ωk0 and a largest Hubble constant h; in contrast, BAO1 data always give a largest Ωm0, a smallest Ωk0 and a smallest h. （2） For the wCDM and the CPL model, NO BAO data always give a largest EoS w; in contrast, BA02 data always give a smallest w. （3） Compared with the case of BAO1, BAO2 data always give a slightly larger FoM, and thus can give a cosmological constraint with a slightly better accuracy. （4） The impacts of different BAO data on the cosmic evolution and the comic age are very small, and cannot be distinguished by using various dark energy diagnoses and the cosmic age data.
基金Supported by National Natural Science Fund of China(11603005,11775038,11647307,11675182,11690022)
文摘We constrain three cosmological models - the concordance cold dark matter plus cosmological constant（ΛCDM） model, the power-law（PL） model, and the Rh =ct model - using the available local probes, which include the JLA compilation of type-Ia supernovae（SNe Ia）, the direct measurement of the Hubble constant（Hz）, and the baryon acoustic oscillations（BAO）. For the ΛCDM model, we consider two different cases, i.e. zero and non-zero spatial curvature. We find that by using the JLA alone, the ΛCDM and PL models are indistinguishable, but the Rh =ct model is strongly disfavored. If we combine JLA＋Hz, the ΛCDM model is strongly favored over the other two models. The combination of all three datasets supports ΛCDM as the best model. We also use the low-redshift（z 〈0.2） data to constrain the deceleration parameter using the cosmography method, and find that only the ΛCDM model is consistent with cosmography. However, there is no strong evidence to distinguish between flat and non-flatΛCDM models by using the local data alone.
基金Supported in part by the National Natural Science Foundation of China under Grants Nos 10375023 and 10575035, the Programme for NCET under Grant No 04-0784, the Key Project of the Ministry of Education of China （No 205110）, and the Doctor Foundation of CSUFT.
文摘We investigate the constraints on a generalized Chaplygin gas （GCG） model using the gold sample type-Ia supernovae （She Ia） data, the new Supernova Legacy Survey （SNLS） Sne Ia data and the size of baryonic acoustic oscillation peak found in Sloan Digital Sky Survey （SDSS）. In a spatially flat universe case we obtain, at a 95.4% confidence level, A8 = 0.76^＋0.07 -0.07 and α= 0.028^＋0.322 -0.2382 Our results are consistent with the ACDM model （α= 0）, but rule out the standard Chaplygin gas model （α= 1）.
基金UGC, ERO, Kolkata for financial assistance to carry out the Minor Research Project [No. F. PSO-003/08-09(ERO), dt. 05-12-2008] awarded during the XI plan period
文摘Non-static inhomogeneous cosmological models are obtained in general relativity for the case of a plane symmetric massless scalar field with cosmological constant A, when the source of the gravitational field is a viscous fluid. Some physical and geometrical behaviors of the solutions are also discussed.
