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Cosmological Constant and Stability of the Cosmological Models 被引量:1
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作者 WANGYong-Jiu TANGZhi-Ming 《Communications in Theoretical Physics》 SCIE CAS CSCD 2002年第6期667-670,共4页
The importance of cosmological constant for the cosmological models is given. The variations of the cosmological model for parameters and were discussed respectively. Near , the cosmological model is unstable with t... The importance of cosmological constant for the cosmological models is given. The variations of the cosmological model for parameters and were discussed respectively. Near , the cosmological model is unstable with the change of , and near , the cosmological model is unstable with the change of . So when we consider the stable cosmological model, we must consider the nonzero cosmological constant. 展开更多
关键词 COSMOLOGY cosmological models general relativity
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Bianchi-Type II String Cosmological Models with Bulk Viscosity 被引量:1
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作者 WANGXing-Xiang 《Communications in Theoretical Physics》 SCIE CAS CSCD 2004年第5期726-728,共3页
The locally rotationally symmetric Bianchi-type II string cosmological models with bulk viscosity are obtained, where an equation of state, , and a relation between metric potentials, , are adopted. The physical featu... The locally rotationally symmetric Bianchi-type II string cosmological models with bulk viscosity are obtained, where an equation of state, , and a relation between metric potentials, , are adopted. The physical features of the models are also discussed. In special cases the model reduces to the string models without viscosity that was previously given in the literatures. 展开更多
关键词 string cosmological model Bianchi-type II space-time bulk viscosity
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A Solution to the Cosmological Constant Problem Using the Holographic Principle (A Brief Note)
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作者 Eugene Terry Tatum 《Journal of Modern Physics》 2024年第2期159-166,共8页
This paper integrates a quantum conception of the Planck epoch early universe with FSC model formulae and the holographic principle, to offer a reasonable explanation and solution of the cosmological constant problem.... This paper integrates a quantum conception of the Planck epoch early universe with FSC model formulae and the holographic principle, to offer a reasonable explanation and solution of the cosmological constant problem. Such a solution does not appear to be achievable in cosmological models which do not integrate black hole formulae with quantum formulae such as the Stephan-Boltzmann law. As demonstrated herein, assuming a constant value of Lambda over the great span of cosmic time appears to have been a mistake. It appears that Einstein’s assumption of a constant, in terms of vacuum energy density, was not only a mistake for a statically-balanced universe, but also a mistake for a dynamically-expanding universe. 展开更多
关键词 Quantum Cosmology Planck Scale cosmological Constant Black Holes Holographic Principle Flat Space Cosmology AdS-CFT ER = EPR Cosmology Model
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Applying the Stefan-Boltzmann Law to a Cosmological Model (a Brief Note)
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作者 Eugene Terry Tatum 《Journal of Modern Physics》 2024年第11期1717-1722,共6页
This brief note brings the reader up-to-date with the recent successes of the new Haug-Tatum cosmology model. In particular, the significance of recent proof that the Stefan-Boltzmann law applies to such a model is em... This brief note brings the reader up-to-date with the recent successes of the new Haug-Tatum cosmology model. In particular, the significance of recent proof that the Stefan-Boltzmann law applies to such a model is emphasized and a rationale for this is given. Remarkably, the proposed solutions of this model have incorporated all 580 supernova redshifts in the Union2 database. Therefore, one can usefully apply this thermodynamic law in the form of a continually expanding black-body universe model. To our knowledge, no other cosmological model has achieved such high-precision observational correlation. 展开更多
关键词 Haug-Tatum Cosmology Stefan-Boltzmann Law Flat Space Cosmology CMB Cosmic Thermodynamics Rh = ct Cosmology Model Black Body
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Cosmological Model in Four Time and Four Space Dimensions
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作者 Juan Antonio Nieto 《Journal of Applied Mathematics and Physics》 2024年第3期829-840,共12页
We develop a cosmological model in a physical background scenario of four time and four space dimensions ((4+4)-dimensions or (4+4)-universe). We show that in this framework the (1+3)-universe is deeply connected with... We develop a cosmological model in a physical background scenario of four time and four space dimensions ((4+4)-dimensions or (4+4)-universe). We show that in this framework the (1+3)-universe is deeply connected with the (3+1)-universe. We argue that this means that in the (4+4)-universe there exists a duality relation between the (1+3)-universe and the (3+1)-universe. 展开更多
关键词 cosmological Model (4+4)-Dimensions Duality Symmetry
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Entropy and Cosmological Constant of a Universe Calculated by Means of Dimensional Analysis, Margolus-Levitin Theorem and Landauer’s Principle
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作者 Mario Leo 《Journal of Modern Physics》 2023年第10期1310-1322,共13页
By means of the dimensional analysis a spherically simmetric universe with a mass M = c<sup>3</sup>/(2HG) and radius equal to c/H is considered, where H is the Hubble constant, c the speed of light and G t... By means of the dimensional analysis a spherically simmetric universe with a mass M = c<sup>3</sup>/(2HG) and radius equal to c/H is considered, where H is the Hubble constant, c the speed of light and G the Newton gravitational constant. The density corresponding to this mass is equal to the critical density ρ<sub>cr </sub>= 3H<sup>2</sup>/(8πG). This universe evolves according to a Bondi-Gold-Hoyle scenario, with continuous creation of matter at a rate such to maintain, during the expansion, the density always critical density. Using the Margolus-Levitin theorem and the Landauer’s principle, an entropy is associated with this universe, obtaining a formula having the same structure as the Bekenstein-Hawking formula of the entropy of a black hole. Furthermore, a time-dependent cosmological constant Λ, function of the Hubble constant and the speed of light, is proposed. 展开更多
关键词 cosmological models cosmological Constant ENTROPY
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The “Dead Universe” Theory: Natural Separation of Galaxies Driven by the Remnants of a Supermassive Dead Universe
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作者 Joel Almeida 《Natural Science》 2024年第6期65-101,共37页
This article explores the dead universe theory as a novel interpretation for the origin and evolution of the universe, suggesting that our cosmos may have originated from the remnants of a preceding universe. This per... This article explores the dead universe theory as a novel interpretation for the origin and evolution of the universe, suggesting that our cosmos may have originated from the remnants of a preceding universe. This perspective challenges the conventional Big Bang theory, particularly concerning dark matter, the expansion of the universe, and the interpretation of phenomena such as gravitational waves. 展开更多
关键词 Dead Universe Theory Heat Death of the Universe Big Bang Theory Universe’s Ultimate Fate Universe Expansion Big Freeze Universe cosmological models End of Universe Theories Natural Galaxy Drift Future of the Universe Universe Cooling Down Cosmology and Entropy
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The Hawking Hubble Temperature as the Minimum Temperature, the Planck Temperature as the Maximum Temperature, and the CMB Temperature as Their Geometric Mean Temperature
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作者 Espen Gaarder Haug Eugene Terry Tatum 《Journal of Applied Mathematics and Physics》 2024年第10期3328-3348,共21页
Using a rigorous mathematical approach, we demonstrate how the Cosmic Microwave Background (CMB) temperature could simply be a form of geometric mean temperature between the minimum time-dependent Hawking Hubble tempe... Using a rigorous mathematical approach, we demonstrate how the Cosmic Microwave Background (CMB) temperature could simply be a form of geometric mean temperature between the minimum time-dependent Hawking Hubble temperature and the maximum Planck temperature of the expanding universe over the course of cosmic time. This mathematical discovery suggests a re-consideration of Rh=ctcosmological models, including black hole cosmological models, even if it possibly could also be consistent with the Λ-CDM model. Most importantly, this paper contributes to the growing literature in the past year asserting a tightly constrained mathematical relationship between the CMB temperature, the Hubble constant, and other global parameters of the Hubble sphere. Our approach suggests a solid theoretical framework for predicting and understanding the CMB temperature rather than solely observing it.1. 展开更多
关键词 Hawking Temperature Planck Temperature CMB Temperature Geometric Mean Compton Wavelength Hubble Sphere cosmological models
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Black Hole Complementarity in Terms of the Outsider and Insider Perspectives
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作者 Eugene Terry Tatum 《Journal of Modern Physics》 2024年第2期184-192,共9页
A complementarity hypothesis concerning outsider and insider perspectives of a gargantuan black hole is proposed. The two thought experiments presented herein are followed by a brief discussion of a new interpretation... A complementarity hypothesis concerning outsider and insider perspectives of a gargantuan black hole is proposed. The two thought experiments presented herein are followed by a brief discussion of a new interpretation of black hole interior “space-and-time-reversal”. Specifically, it is proposed that the “singularity” space of the black hole interior is time-like and the expansion time of the black hole interior is space-like. The resemblance of this new insider interpretation to our own expanding and redshifting big bang universe is compelling. 展开更多
关键词 Black Holes Complementarity cosmological models Rh = ct models Flat Space Cosmology Schwarzschild Cosmology Thought Experiment Dark Energy Quantum Vacuum
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Accelerating dark energy models with anisotropic fluid in Bianchi type Ⅵ_0 space-time
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作者 Anirudh Pradhan 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2013年第2期139-158,共20页
Motivated by the increasing evidence for the need of a geometry that re- sembles Bianchi morphology to explain the observed anisotropy in the WMAP data, we have discussed some features of Bianchi type VI0 universes in... Motivated by the increasing evidence for the need of a geometry that re- sembles Bianchi morphology to explain the observed anisotropy in the WMAP data, we have discussed some features of Bianchi type VI0 universes in the presence of a fluid that has an anisotropic equation of state (EoS) parameter in general relativity. We present two accelerating dark energy (DE) models with an anisotropic fluid in Bianchi type VI0 space-time. To ensure a deterministic solution, we choose the scale factor a(t) = √tnet, which yields a time-dependent deceleration parameter, representing a class of models which generate a transition of the universe from the early decelerating phase to the recent accelerating phase. Under suitable conditions, the anisotropic mod- els approach an isotropic scenario. The EoS for DE co is found to be time-dependent and its existing range for derived models is in good agreement with data from recent observations of type Ia supernovae (SNe Ia) (Knop et al. 2003), SNe Ia data com- bined with cosmic microwave background (CMB) anisotropy and galaxy clustering statistics (Tegmark et al. 2004a), as well as the latest combination of cosmological datasets coming from CMB anisotropies, luminosity distances of high redshift SNe Ia and galaxy clustering. For different values of n, we can generate a class of physically viable DE models. The cosmological constant A is found to be a positive decreasing function of time and it approaches a small positive value at late time (i.e. the present epoch), which is corroborated by results from recent SN Ia observations. We also ob- serve that our solutions are stable. The physical and geometric aspects of both models are also discussed in detail. 展开更多
关键词 cosmological models -- dark energy -- variable EoS parameter
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Anisotropic Plane Symmetric Two-Fluid Cosmological Model with Time-Varying G and A
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作者 Verma M. K. Chandel S. Ram Shri 《Chinese Physics Letters》 SCIE CAS CSCD 2015年第12期1-4,共4页
We investigate a two-fluid anisotropic plane symmetric cosmological model with variable gravitational constant G(t) and cosmological term A(t). In the two-fluid model, one fluid is chosen to be that of the radiati... We investigate a two-fluid anisotropic plane symmetric cosmological model with variable gravitational constant G(t) and cosmological term A(t). In the two-fluid model, one fluid is chosen to be that of the radiation field modeling the cosmic microwave background and the other one a perfect fluid modeling the material content of the universe. Exact solutions of the field equations are obtained by using a special form for the average scale factor which corresponds to a specific time-varying deceleration parameter. The model obtained presents a cosmological scenario which describes an early acceleration and late-time deceleration. The gravitation constant increases with the cosmic time whereas the cosmological term decreases and asymptotically tends to zero. The physical and kinematical behaviors of the associated fluid parameters are discussed. 展开更多
关键词 Anisotropic Plane Symmetric Two-Fluid cosmological Model with Time-Varying G and A FRW
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Anisotropic Standard Decelerating Cosmological Model with Quadratic Equation of State
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作者 Mohammad Moksud Alam Mohammed Aman Ullah S M Erfanul Kabir Chowdhury 《Journal of Applied Mathematics and Physics》 2020年第9期1990-1998,共9页
Spatially homogeneous and anisotropic Bianchi type-I cosmological model containing perfect fluid with quadratic equation of state has been diagnosed in general theory of relativity. To obtain a deterministic solution,... Spatially homogeneous and anisotropic Bianchi type-I cosmological model containing perfect fluid with quadratic equation of state has been diagnosed in general theory of relativity. To obtain a deterministic solution, we have used a relation between metric potentials. The exact solution of Einstein’s field equations thus obtained represents an expanding and decelerating universe. The physical and kinematical parameters of the model have also been analyzed with certain constrained between the parameters of the quadratic equation of state. 展开更多
关键词 General Relativity Bianchi Type-I cosmological Model Quadratic Equation of State (EoS)
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An interacting two-fluid scenario for dark energy in a Bianchi type-I cosmological model
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作者 Triloki Singh Raghavendra Chaubey 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2012年第5期473-484,共12页
We study the evolution of the dark energy parameter within a Bianchi type-I cosmological model filled with barotropic fluid and dark energy. The solutions have been obtained for power law and exponential forms of the ... We study the evolution of the dark energy parameter within a Bianchi type-I cosmological model filled with barotropic fluid and dark energy. The solutions have been obtained for power law and exponential forms of the expansion parameter (they correspond to a constant deceleration parameter in general relativity). After a long time, the models tend to be isotropic under certain conditions. 展开更多
关键词 cosmological model -- dark energy parameter -- barotropic fluid
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Dynamical Evolution of Modified Chaplygin Gas 被引量:1
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作者 付明慧 吴亚波 贺敬 《Chinese Physics Letters》 SCIE CAS CSCD 2008年第2期798-801,共4页
Based our previous work [Mod. Phys. Lett. A 22 (2007) 783, Gen. Relat. Gray. 39 (2007) 653], some properties of modified Chaplygin gas (MCG) as a dark energy model continue to be studied mainly in two aspects: ... Based our previous work [Mod. Phys. Lett. A 22 (2007) 783, Gen. Relat. Gray. 39 (2007) 653], some properties of modified Chaplygin gas (MCG) as a dark energy model continue to be studied mainly in two aspects: one is the change rates of the energy density and energy transfer, and the other is the evolution of the growth index. It is pointed that the density of dark energy undergoes the change from decrease to increase no matter whether the interaction between dark energy and dark matter exists or not, but the corresponding transformation points are different from each other.Eurthermore, it is stressed that the MCG model even supports the existence of interaction between dark energy and dark matter, and the energy of transfer flows from dark energy to dark matter. The evolution of the interaction term with an ansatz 3Hc^2ρ is discussed with the MCG model. Moreover, the evolution of the growth index f in the MCG model without interaction is illustrated, from which we find that the evolutionary trajectory of f overlaps with that of the ACDM model when a 〉 0.7 and its theoretical value f ≈ 0.566 given by us at z = 0.15 is consistent with the observations. 展开更多
关键词 cosmological models CONSTRAINTS
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The Hubble Constant Problem and the Solution by Gravitation in Flat Space-Time 被引量:1
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作者 Walter Petry 《Journal of Modern Physics》 2020年第2期214-220,共7页
General Relativity implies an expanding Universe from a singularity, the so-called Big Bang. The rate of expansion is the Hubble constant. There are two major ways of measuring the expansion of the Universe: through t... General Relativity implies an expanding Universe from a singularity, the so-called Big Bang. The rate of expansion is the Hubble constant. There are two major ways of measuring the expansion of the Universe: through the cosmic distance ladder and through looking at the signals originated from the beginning of the Universe. These two methods give quite different results for the Hubble constant. Hence, the Universe doesn’t expand. The solution to this problem is the theory of gravitation in flat space-time where space isn’t expanding. All the results of gravitation for weak fields of this theory agree with those of General Relativity to measurable accuracy whereas at the beginning of the Universe the results of both theories are quite different, i.e. no singularity by gravitation in flat space-time and non-expanding universe, and a Big Bang (singularity) by General Relativity. 展开更多
关键词 Gravitation in Flat Space-Time cosmological models Hubble Constant No Big Bang No Singularity Non-Expanding Universe
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Constraining Brans–Dicke Cosmology with the CSST Galaxy Clustering Spectroscopic Survey
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作者 Anda Chen Yan Gong +2 位作者 Fengquan Wu Yougang Wang Xuelei Chen 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2022年第5期190-198,共9页
The Brans-Dicke(BD)theory is the simplest Scalar-Tensor theory of gravity,which can be considered as a candidate of modified Einstein’s theory of general relativity.In this work,we forecast the constraints on BD theo... The Brans-Dicke(BD)theory is the simplest Scalar-Tensor theory of gravity,which can be considered as a candidate of modified Einstein’s theory of general relativity.In this work,we forecast the constraints on BD theory in the CSST galaxy clustering spectroscopic survey with a magnitude limit~23 AB mag for point-source 5σdetection.We generate mock data based on the zCOSMOS catalog and consider the observational and instrumental effects of the CSST spectroscopic survey.We predict galaxy power spectra in the BD theory from z=0 to 1.5,and the galaxy bias and other systematical parameters are also included.The Markov Chain Monte Carlo technique is employed to find the best-fits and probability distributions of the cosmological and systematical parameters.A BD parameterζis introduced,which satisfiesζ=In(1+(1/ω)).We find that the CSST spectroscopic galaxy clustering survey can give|ξ|<10^(-2),or equivalently|ω|>O(10^(2))and|■/G|<10^(-13),under the assumptionζ=0.These constraints are almost at the same order of magnitude compared to the joint constraints using the current cosmic microwave background,baryon acoustic oscillations and TypeⅠa supernova data,indicating that the CSST galaxy clustering spectroscopic survey would be powerful for constraining the BD theory and other modified gravity theories. 展开更多
关键词 cosmology -cosmological models -cosmological parameters from large-scale structure
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MOUND: An Alternative to Milgrom’s MOND
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作者 Patrick G. Tonin 《International Journal of Astronomy and Astrophysics》 2021年第1期87-94,共8页
We test and explore a Modified Universe Dynamics (MOUND) formula recently proposed by the author. We show that, similarly to Milgrom’s Modified Newtonian Dynamics (MOND), it is successful in accounting for the mass d... We test and explore a Modified Universe Dynamics (MOUND) formula recently proposed by the author. We show that, similarly to Milgrom’s Modified Newtonian Dynamics (MOND), it is successful in accounting for the mass discrepancy in spiral galaxies, and it predicts the Baryonic Tully-Fisher Relation (BTFR) and the Radial Acceleration Relation (RAR). Contrary to Milgrom’s MOND, MOUND also explains the dynamics of galaxy clusters and does not rely on an empirical interpolating function or an ad hoc acceleration parameter. 展开更多
关键词 cosmological models Dark Matter Modified Newtonian Dynamics
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An interacting scenario for dark energy in a Bianchi type-I universe 被引量:1
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作者 Hassan Amirhashchi Syed Nasrullah Ali Qazi Hishamuddin Zainuddin 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2014年第11期1383-1392,共10页
We study the interaction between dark energy (DE) and dark matter in the scope of anisotropic Bianchi type-I space-time. First we derive the general form of the DE equation of state (EoS) parameter in both non-int... We study the interaction between dark energy (DE) and dark matter in the scope of anisotropic Bianchi type-I space-time. First we derive the general form of the DE equation of state (EoS) parameter in both non-interacting and interacting cases and then we examine its future by applying a hyperbolic scale factor. It is shown that in the non-interacting case, depending on the value of the anisotropy parameter K, the DE EoS parameter varies from phantom to quintessence whereas in the interacting case the EoS parameter varies in the quintessence region. However, in both cases, the DE EoS parameter ωde ultimately (i.e. at z : -1) tends to the cosmological constant (ωde = -1). Moreover, we fix the cosmological bound on the anisotropy parameter K by using recent observational data about the Hubble parameter. 展开更多
关键词 cosmology: Bianchi type-I model -- dark energy -- dark matter
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Modelling and Analysis of the Hubble Diagram of 280 Type SNIa Supernovae and Gamma Ray Bursts Redshifts with Analytical and Empirical Redshift/Magnitude Functions 被引量:2
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作者 Laszlo A. Marosi 《International Journal of Astronomy and Astrophysics》 2016年第3期272-275,共5页
Based on an analysis of 280 Type SNIa supernovae and gamma-ray bursts redshifts in the range of z = 0.0104 - 8.1 the Hubble diagram is shown to follow a strictly exponential slope predicting an exponentially expanding... Based on an analysis of 280 Type SNIa supernovae and gamma-ray bursts redshifts in the range of z = 0.0104 - 8.1 the Hubble diagram is shown to follow a strictly exponential slope predicting an exponentially expanding or static universe. At redshifts > 2 - 3 ΛCDM models show a poor agreement with the observed data. Based on the results presented in this paper, the Hubble diagram test does not necessarily support the idea of expansion according to the big-bang concordance model. 展开更多
关键词 MAGNITUDE Redshift Data Fitting SUPERNOVAE Gamma Ray Bursts Hubble Diagram ΛCDM cosmological Model
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The interpretation of the CMBR
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作者 Yi-Jia Zheng 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2021年第9期180-184,共5页
In the popular ACDM model,the cosmic microwave background radiation(CMBR)is thought to be the remnant of the early hot universe.An important precondition of this interpretation of CMBR is:after the last scattering sur... In the popular ACDM model,the cosmic microwave background radiation(CMBR)is thought to be the remnant of the early hot universe.An important precondition of this interpretation of CMBR is:after the last scattering surface formed,the high temperature ionized gases in the universe became low temperature neutral gases and so the universe has been completely transparent to the radiation which comes from the hot early universe.However,observations show that today most gases in the universe are still in a high temperature ionized state.The universe is not completely transparent to the radiation which comes from the hot early universe.According to the famous Sunyaev-Zeldovich effect,if the CMBR comes from the early hot universe and follows a perfect blackbody spectrum,the free electrons in the cosmic plasma will distort the perfect blackbody spectrum of the CMBR.In this case,the observed CMBR cannot be of a perfect blackbody spectrum.This is a fatal flaw in the interpretation of CMBR using the ACDM model.In order to overcome this fatal flaw,in this paper it is proposed that in the ACDM model frame,a better interpretation of CMBR is:The CMBR is a thermal equilibrium product between the high temperature ionized gases and the cosmic radiation field in the local universe space. 展开更多
关键词 cosmology:theory cosmological model cosmic microwave background radiation
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