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Prospects of the Multi-channel Photometric Survey Telescope in the Cosmological Application of Type Ia Supernovae
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作者 Zhenyu Wang Jujia Zhang +1 位作者 Xinzhong Er Jinming Bai 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第4期183-191,共9页
The Multi-channel Photometric Survey Telescope(Mephisto)is a real-time,three-color photometric system designed to capture the color evolution of stars and transients accurately.This telescope system can be crucial in ... The Multi-channel Photometric Survey Telescope(Mephisto)is a real-time,three-color photometric system designed to capture the color evolution of stars and transients accurately.This telescope system can be crucial in cosmological distance measurements of low-redshift(low-z,z■0.1)Type Ia supernovae(SNe Ia).To optimize the capabilities of this instrument,we perform a comprehensive simulation study before its official operation is scheduled to start.By considering the impact of atmospheric extinction,weather conditions,and the lunar phase at the observing site involving the instrumental features,we simulate light curves of SNe Ia obtained by Mephisto.The best strategy in the case of SN Ia cosmology is to take the image at an exposure time of 130 s with a cadence of 3 days.In this condition,Mephisto can obtain hundreds of high-quality SNe Ia to achieve a distance measurement better than 4.5%.Given the on-time spectral classification and monitoring of the Lijiang 2.4 m Telescope at the same observatory,Mephisto,in the whole operation,can significantly enrich the well-calibrated sample of supernovae at low-z and improve the calibration accuracy of high-z SNe Ia. 展开更多
关键词 (stars:)supernovae:general (cosmology:)cosmological parameters telescopes
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The Extremal Universe Exact Solution from Einstein’s Field Equation Gives the Cosmological Constant Directly
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作者 Espen Gaarder Haug 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第1期386-397,共12页
Einstein’s field equation is a highly general equation consisting of sixteen equations. However, the equation itself provides limited information about the universe unless it is solved with different boundary conditi... Einstein’s field equation is a highly general equation consisting of sixteen equations. However, the equation itself provides limited information about the universe unless it is solved with different boundary conditions. Multiple solutions have been utilized to predict cosmic scales, and among them, the Friedmann-Lemaître-Robertson-Walker solution that is the back-bone of the development into today standard model of modern cosmology: The Λ-CDM model. However, this is naturally not the only solution to Einstein’s field equation. We will investigate the extremal solutions of the Reissner-Nordström, Kerr, and Kerr-Newman metrics. Interestingly, in their extremal cases, these solutions yield identical predictions for horizons and escape velocity. These solutions can be employed to formulate a new cosmological model that resembles the Friedmann equation. However, a significant distinction arises in the extremal universe solution, which does not necessitate the ad hoc insertion of the cosmological constant;instead, it emerges naturally from the derivation itself. To the best of our knowledge, all other solutions relying on the cosmological constant do so by initially ad hoc inserting it into Einstein’s field equation. This clarification unveils the true nature of the cosmological constant, suggesting that it serves as a correction factor for strong gravitational fields, accurately predicting real-world cosmological phenomena only within the extremal solutions of the discussed metrics, all derived strictly from Einstein’s field equation. 展开更多
关键词 General Relativity Theory Cosmological Constant Extremal Solution Reissner-Nordström KERR Kerr-Newman
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Hubble Tension Explanation from This Cosmological Model AΛΩ (Slow Bang Model, SB)
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作者 Jean Perron 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第1期106-125,共20页
In this article we present a model of Hubble-Lemaître law using the notions of a transmitter (galaxy) and a receiver (MW) coupled to a model of the universe (Slow Bang Model, SB), based on a quantum approach of t... In this article we present a model of Hubble-Lemaître law using the notions of a transmitter (galaxy) and a receiver (MW) coupled to a model of the universe (Slow Bang Model, SB), based on a quantum approach of the evolution of space-time as well as an equation of state that retains all the infinitesimal terms. We find an explanation of the Hubble tension H<sub>0</sub>. Indeed, we have seen that this constant depends on the transceiver pair which can vary from the lowest observable value, from photons of the CMB (theoretical [km/s/Mpc]) to increasingly higher values depending on the earlier origin of the formation of the observed galaxy or cluster (ETG ~0.3 [Gy], ~74 [km/s/Mpc]). We have produced a theoretical table of the values of the constant according to the possible pairs of transmitter/receiver in the case where these galaxies follow the Hubble flow without large disturbance. The calculated theoretical values of the constant are in the order of magnitude of all values mentioned in past studies. Subsequently, we applied the models to 9 galaxies and COMA cluster and found that the models predict acceptable values of their distances and Hubble constant since these galaxies mainly follow the Hubble flow rather than the effects of a galaxy cluster or a group of clusters. In conclusion, we affirm that this Hubble tension does not really exist and it is rather the understanding of the meaning of this constant that is questioned. 展开更多
关键词 Model of the Universe Cosmological Constant Hubble Constant Hubble’s Tension Hubble-Lemaître Law Hubble’s Flow
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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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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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Adiabaticity Violated Not Enough: Presume Primordial Black Holes to Generate Gravitons for Cosmological Constant, as Candidate for DE Initially
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作者 Andrew Walcott Beckwith 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2023年第1期100-107,共8页
Instant preheating as given in terms of window where adiabaticity is violated is a completely inefficient form of particle production if we use Padmandabhan scalar potentials. This necessitates using a very different ... Instant preheating as given in terms of window where adiabaticity is violated is a completely inefficient form of particle production if we use Padmandabhan scalar potentials. This necessitates using a very different mechanism for early universe gravition production as an example which is to break up the initial “mass” formed about 10<sup>60</sup> times Planck mass into graviton emitting 10<sup>5</sup> gram sized micro black holes. The mechanism is to assume that we have a different condition than the usual adiabaticity idea which is connected with reheating of the universe. Hence, we will be looking at an earlier primordial black hole generation for generation of gravitons. 展开更多
关键词 Black Holes Cosmological Constant Universe Gravition
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Cosmological Inconstant, Supernovae 1a and Decelerating Expansion
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作者 Russell Bagdoo 《Journal of Modern Physics》 CAS 2023年第5期692-721,共30页
In 1998, two groups of astronomers, one led by Saul Perlmutter and the other by Brian Schmidt, set out to determine the deceleration—and hence the total mass/energy—of the universe by measuring the recession speeds ... In 1998, two groups of astronomers, one led by Saul Perlmutter and the other by Brian Schmidt, set out to determine the deceleration—and hence the total mass/energy—of the universe by measuring the recession speeds of type la supernovae (SN1a), came to an unexpected conclusion: ever since the universe was about 7 billion years old, its expansion rate has not been decelerating. Instead, the expansion rate has been speeding up. To justify this acceleration, they suggested that the universe does have a mysterious dark energy and they have emerged from oblivion the cosmological constant, positive this time, which is consistent with the image of an inflationary universe. To explain the observed dimming of high-redshift SN1a they have bet essentially on their distance revised upwards. We consider that an accelerated expansion leads right to a “dark energy catastrophe” (i.e., the chasm between the current cosmological vacuum density value of 10 GeV/m<sup>3</sup> and the vacuum energy density proposed by quantum field theory of ~10<sup>122</sup> GeV/m<sup>3</sup>). We suppose rather that the universe knows a slowdown expansion under the positive pressure of a dark energy, otherwise called a variable cosmological constant. The dark luminosity of the latter would be that of a “tired light” which has lost energy with distance. As for the low brilliance of SN1a, it is explained by two physical processes: The first relates to their intrinsic brightness—supposedly do not vary over time—which would depend on the chemical conditions which change with the temporal evolution;the second would concern their apparent luminosity. Besides the serious arguments already known, we strongly propose that their luminosity continually fades by interactions with cosmic magnetic fields, like the earthly PVLAS experiment which loses much more laser photons than expected by crossing a magnetic field. It goes in the sense of a “tired light” which has lost energy with distance, and therefore, a decelerated expansion of the universe. Moreover, we propose the “centrist” principle to complete the hypothesis of the cosmological principle of homogeneity and isotropy considered verified. Without denying the Copernican principle, he is opposed to a “spatial” theoretical construction which accelerates the world towards infinity. The centrist principle gives a “temporal” and privileged vision which tends to demonstrate the deceleration of expansion. 展开更多
关键词 Variable Cosmological Constant SN1a Dark Energy Catastrophe Theory of Relation Deceleration of the Expansion PVLAS Experiment Tired Light Centrist Principle
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The Evolving Absolute Magnitude of Type 1a Supernovae and Its Critical Impact on the Cosmological Parameters
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作者 Abraham P. Mahtessian Garen S. Karapetian +1 位作者 Martik A. Hovhannisyan Lazar A. Mahtessian 《International Journal of Astronomy and Astrophysics》 2023年第2期39-60,共22页
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
关键词 Supernovae SNe1a Cosmological Parameters COSMOLOGY ACCELERATION
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ETG Galaxies (<400 [My]) from JWST Already Predicted in 2019 from This Cosmological Model AΛΩ (Slow Bang Model, SB)
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作者 Jean Perron 《Journal of High Energy Physics, Gravitation and Cosmology》 2023年第3期800-834,共35页
A model of the universe (preprint 2019), based on a quantum approach to the evolution of space-time as well as on an equation of state that retains all the infinitesimal terms, has made it possible to estimate a large... A model of the universe (preprint 2019), based on a quantum approach to the evolution of space-time as well as on an equation of state that retains all the infinitesimal terms, has made it possible to estimate a large number of parameters relating to the universe and in particular the estimation of a colossal phantom energy E<sub>Λ</sub> represented by the existence of a hidden photon &ycirc;present everywhere. This energy undergoes dilution in H<sup>4</sup> due to expansion of the universe. In order to introduce the effects of this energy on the curvature of space-time, we chose to express it by the cosmological constant Λ in the equation of the GR via the element tensor T<sup>00</sup>. This positive energy E<sub>Λ</sub> which acts as additional effect to gravity and we have expressed this energy in the form of an equation which expresses a so-called cosmological force F<sub>Λ</sub>. We estimated that this photon or hidden particle of spin 1 has an energy ~1 [meV] at our cosmic position t<sub>0</sub> which makes it an ultra-light axion ULA. Subsequently, with the action of this augmented force, especially in the first 400 [My] we were able to explain, in part, the rapid development of galaxy formation as seen by JWST as well as several observed dynamic behaviors of the barionic mass of some galaxies as MW, M33, UGC12591, NGC3198, UGC2885 and NGC253 whose observations raise questions and require additional explanations that led to the likely existence of unobserved matter called DM. However, it appears that this cosmological force makes it possible to explain several observations without the use of this DM. A first conclusion was drawn, namely the much earlier formation of galaxies by the action of this cosmological force coupled with gravity (GLASS z12). In addition, the model made it possible to explain the need or not to use the concept of DM for ETGs and LTGs by the more or less early and long period of the beginning of galaxy formation over a period ranging from ~170 to 1200 [My]. Thus, the model makes it possible to explain to a large extent the observations of the dynamics of the galaxies studied. However, several questions remain. 展开更多
关键词 Model of Universe ETG LTG UDG Cosmological Constant Hidden Photon Hidden Boson GLASS z12
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Mass of the Universe from Quarks: A Plausible Solution to the Cosmological Constant Problem
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作者 Kevin Oramah 《Journal of Modern Physics》 2023年第12期1672-1692,共21页
A framework to estimate the mass of the universe from quarks is presented, taking spacetime into account. This is a link currently missing in our understanding of physics/science. The focus on mass-energy balance is a... A framework to estimate the mass of the universe from quarks is presented, taking spacetime into account. This is a link currently missing in our understanding of physics/science. The focus on mass-energy balance is aimed at finding a solution to the Cosmological Constant (CC) problem by attempting to quantize space-time and linking the vacuum energy density at the beginning of the universe and the current energy density. The CC problem is the famous disagreement of approximately 120 orders of magnitude between the theoretical energy density at the Planck scale and the indirectly measured cosmological energy density. Same framework is also used to determine the mass of the proton and neutron from first principles. The only input is the up quark (u-quark) mass, or precisely, the 1st generation quarks. The method assumes that the u-quark is twice as massive as the down-quark (d-quark). The gap equation is the starting point, introduced in its simplest form. The main idea is to assume that all the particles and fields in the unit universe are divided into quarks and everything else. Everything else means all fields and forces present in the universe. It is assumed that everything else can be “quark-quantized”;that is, assume that they can be quantized into similar sizeable u-quarks and/or it’s associated interactions and relations. The result is surprisingly almost as measured and known values. The proton structure and mass composition are also analysed, showing that it likely has more than 3 quarks and more than 3 valence quarks. It is also possible to estimate the percentage of dark matter, dark energy, ordinary matter, and anti-matter. Finally, the cosmological constant problem or puzzle is resolved by connecting the vacuum energy density of Quantum Field Theory (5.1E+96 kg/m<sup>3</sup>) and the energy density of General Relativity (1.04E−26 kg/m<sup>3</sup>). Upon maturation, this framework can serve as a bridging platform between Quantum Field Theory and General Relativity. Other aspects of natures’ field theories can be successfully ported to the platform. It also increases the chances of solving some of the unanswered questions in physics. 展开更多
关键词 Cosmological Constant Proton Mass-Structure Quark-Quantization Dark Matter Dark Energy Age of the Universe Energy Density Spacetime Quantization
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Cosmological application on five-dimensional teleparallel theory equivalent to general relativity
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作者 Gamal G.L.Nashed 《Chinese Physics B》 SCIE EI CAS CSCD 2012年第10期122-129,共8页
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
关键词 5D teleparallel equivalent of general relativity 5D solutions cosmological parameters cosmological problems
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From Poincaré’s Electro-Gravific Ether (1905) to Cosmological Background Radiation (3°K, 1965)
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作者 Yves Pierseaux 《Journal of Modern Physics》 2020年第9期1410-1427,共18页
<p align="justify"> <span style="font-family:Verdana;"></span><span style="font-family:Verdana;"></span>It is well known that Einstein published in June 1905... <p align="justify"> <span style="font-family:Verdana;"></span><span style="font-family:Verdana;"></span>It is well known that Einstein published in June 1905 his theory of Special Relativity (SR) without entirely based on space-time Lorentz Transformation (LT) with invariance of Light Velocity. It is much less known that Poincaré published, practically at the same time, a SR also based entirely on LT with also an invariant velocity. However, according to Poincaré, the invariant is not only that of light wave but also that of Gravific Wave in Ether. Poincaré’s Gravific ether exerts also a Gravific pressure, in the same paper, on <i>charged </i>(e) Electron (a “Hole in Ether” according to Poincaré). There are thus two SR: That of Einstein (ESR), without ether and without gravitation, and that of Poincaré (PSR), with Electro-Gravific-Ether. The crucial question arises then: Does “SPECIAL” Poincaré’s (e)-G field fall in the framework of Einstein’s GENERAL Relativity? Our answer is positive. On the basis of Einstein’s equation of gravitation (1917) with Minkowskian Metric (MM) and Zero Constant Cosmological (CC) we rediscover usual Static Vacuum (without <i>charge e </i>of electron). On the other hand with MM and <i>Non-Zero </i>CC, we discover the gravific field of a Cosmological Black Hole (CBH) with density of dark energy compatible with expanding vacuum. Hawking’s Stellar Black Hole (SBH) emits outgoing Black Radiation, whilst Poincaré’s CBH emits (at time zero) incoming Black Radiation. We show that Poincaré’s G-electron involves a (quantum) GRAVITON (on the model of Einstein’s quantum photon) underlying a de Broglie’s G-Wave. There is therefore a Gackground Cosmological model in Poincaré’s basic paper which predicts a density and a temperature of CBR very close to the observed (COBE) values. </p> 展开更多
关键词 Poincaré’s Special Relativity (PSR) with Gravitation PSR in Einstein’s GR with CC Poincaré’s Cosmological Black Hole Poincaré’s Incoming Cosmological Black Radiation versus Hawking’ s Outgoing Stellar Black Radiation Poincaré’s Gravitational Pressure on Electron (“Ge”) Vacuum without Charge e (ESR) Vacuum with Charge e (PSR) Lightlike Quantum Graviton
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Effects of the cosmological constant on chaos in an FRW scalar field universe 被引量:2
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作者 Da-Zhu Ma Xin Wu Shuang-Ying Zhong 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2009年第11期1185-1191,共7页
The dependence of chaos on two parameters of the cosmological constant and the self-interacting coefficient in the imaginary phase space for a closed Friedman- Robertson-Walker (FRW) universe with a conformally coup... The dependence of chaos on two parameters of the cosmological constant and the self-interacting coefficient in the imaginary phase space for a closed Friedman- Robertson-Walker (FRW) universe with a conformally coupled scalar field, as the full understanding of the dependence in real phase space, is investigated numerically. It is found that Poincar6 plots for the two parameters less than 1 are almost the same as those in the absence of the cosmological constant and self-interacting terms. For energies below the energy threshold of 0.5 for the imaginary problem in which there are no cosmological constant and self-interacting terms, an abrupt transition to chaos occurs when at least one of the two parameters is 1. However, the strength of the chaos does not increase for energies larger than the threshold. For other situations of the two parameters larger than 1, chaos is weaker, and even disappears as the two parameters increase. 展开更多
关键词 COSMOLOGY cosmological parameters -- methods NUMERICAL
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Using “Enhanced Quantization” to Bound the Cosmological Constant, and Computing Quantum Number n for Production of 100 Relic Mini Black Holes in a Spherical Region of Emergent Space-Time 被引量:3
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作者 Andrew Walcott Beckwith 《Journal of High Energy Physics, Gravitation and Cosmology》 2018年第3期549-566,共18页
We are looking at comparison of two action integrals and we identify the Lagrangian multiplier as setting up a constraint equation (on cosmological expansion). This is a direct result of the fourth equation of our man... We are looking at comparison of two action integrals and we identify the Lagrangian multiplier as setting up a constraint equation (on cosmological expansion). This is a direct result of the fourth equation of our manuscript which unconventionally compares the action integral of General relativity with the second derived action integral, which then permits Equation (5), which is a bound on the Cosmological constant. What we have done is to replace the Hamber Quantum gravity reference-based action integral with a result from John Klauder’s “Enhanced Quantization”. In doing so, with Padamabhan’s treatment of the inflaton, we then initiate an explicit bound upon the cosmological constant. The other approximation is to use the inflaton results and conflate them with John Klauder’s Action principle for a way, if we have the idea of a potential well, generalized by Klauder, with a wall of space time in the Pre Planckian-regime to ask what bounds the Cosmological constant prior to inflation, and to get an upper bound on the mass of a graviton. We conclude with a redo of a multiverse version of the Penrose cyclic conformal cosmology. Our objective is to show how a value of the rest mass of the heavy graviton is invariant from cycle to cycle. All this is possible due to Equation (4). And we compare all these with results of Reference [1] in the conclusion, while showing its relevance to early universe production of black holes, and the volume of space producing 100 black holes of value about 10^2 times Planck Mass. Initially evaluated in a space-time of about 10^3 Planck length, in spherical length, we assume a starting entropy of about 1000 initially. 展开更多
关键词 INFLATON Action Integral COSMOLOGICAL Constant Penrose Cyclic Cosmology Black Holes Massive GRAVITONS ENHANCED QUANTIZATION
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Combining optical and X-ray observations of galaxy clusters to constrain cosmological parameters 被引量:2
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作者 Heng Yu Zong-Hong Zhu 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2011年第7期776-786,共11页
Galaxy clusters present unique advantages for cosmological study.Here we collect a new sample of 10 lensing galaxy clusters with X-ray observations to constrain cosmological parameters.The redshifts of the lensing clu... Galaxy clusters present unique advantages for cosmological study.Here we collect a new sample of 10 lensing galaxy clusters with X-ray observations to constrain cosmological parameters.The redshifts of the lensing clusters lie between 0.1 and 0.6,and the redshift range of their arcs is from 0.4 to 4.9.These clusters are selected carefully from strong gravitational lensing systems which have both X-ray satellite observations and optical giant luminous arcs with known redshifts.Giant arcs usually appear in the central region of clusters,where mass can be traced with luminosity quite well.Based on gravitational lensing theory and a cluster mass distribution model,we can derive a ratio using two angular diameter distances.One is the distance between lensing sources and the other is that between the deflector and the source. Since angular diameter distance relies heavily on cosmological geometry,we can use these ratios to constrain cosmological models.Moreover,X-ray gas fractions of galaxy clusters can also be a cosmological probe.Because there are a dozen parameters to be fitted,we introduce a new analytic algorithm,Powell's UOBYQA(Unconstrained Optimization By Quadratic Approximation) ,to accelerate our calculation.Our result demonstrates that this algorithm is an effective fitting method for such a continuous multi-parameter constraint.We find an interesting fact that these two approaches are separately sensitive toΩΛandΩM.By combining them,we can get reasonable fitting values of basic cosmological parameters:ΩM=0.26 +0.04 -0.04,andΩΛ=0.82 +0.14 -0.16. 展开更多
关键词 X-rays:galaxies:clusters—gravitational lensing—cosmological parameters
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Robertson-Walker cosmological models with perfect fluid in general relativity 被引量:1
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作者 Rishi Kumar Tiwari 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2011年第7期767-775,共9页
Einstein's field equations with variable gravitational and cosmological constants are considered in the presence of perfect fluid for a Robertson-Walker universe by assuming the cosmological term to be proportional t... Einstein's field equations with variable gravitational and cosmological constants are considered in the presence of perfect fluid for a Robertson-Walker universe by assuming the cosmological term to be proportional to R-m(R is a scale factor and m is a constant).A variety of solutions is presented.The physical significance of the cosmological models has also been discussed. 展开更多
关键词 cosmological parameters—cosmology:variable cosmological term
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How to Use Starobinsky Inflationary Potential Plus Argument from Alder, Bazin, and Schiffer as Radial Acceleration to Obtain First Order Approximation as to Where/When Cosmological Constant May Form 被引量:1
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作者 Andrew Walcott Beckwith 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2022年第4期1012-1018,共7页
Using the Klauder enhanced quantization as a way to specify the cosmological constant as a baseline for the mass of a graviton, we eventually come up and then we will go to the Starobinsky potential as a replacement f... Using the Klauder enhanced quantization as a way to specify the cosmological constant as a baseline for the mass of a graviton, we eventually come up and then we will go to the Starobinsky potential as a replacement for the term N used in Equation (3) and Equation (4). From there we will read in a way to describe conditions allowing for where the cosmological constant may be set. The idea also is to describe a regime of space-time where the initial perturbation/start to inflation actually occurred, as is alluded to in the final part of the document. 展开更多
关键词 Radial Acceleration Cosmological Constant Raviton
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Non Linear Electrodynamics Contributing to a Minimum Vacuum Energy (“Cosmological Constant”) Allowed in Early Universe Cosmology 被引量:3
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作者 Andrew Walcott Beckwith 《Journal of High Energy Physics, Gravitation and Cosmology》 2016年第1期25-32,共8页
This article poses the question of a minimum cosmological constant, i.e. vacuum energy at the start of the cosmological evolution from a near singularity. We pose this comparing formalism as given by Berry (1976) as t... This article poses the question of a minimum cosmological constant, i.e. vacuum energy at the start of the cosmological evolution from a near singularity. We pose this comparing formalism as given by Berry (1976) as to a small time length, and compare that in its entirety to compare this value given by Berry (1976) with a minimum time length at the start of cosmological space-time evolution. Using the methodology of Zeldovich (1972) as to a problem with electron-positron pair production we also propose another upper bound to the problem of minimum time length which may be accessible to experimental inquiry. This then makes the problem of minimum time length a way of specifying a magnetic field dependence of the cosmological constant, which has major implications to answering if quintessence, i.e. a changing cosmological vacuum energy, or a constant for the “cosmological constant” problem. Our answer is an initial value for the cosmological vacuum energy 10<sup>10</sup> - 10<sup>20</sup> times greater than today which suggests either Quintessence, or if still a constant, a much better value for this parameter than what is suggested by traditional field theory methods. In closing we review how our construct supports work done by Corda, as to early universe models and what the implications are, as to the choices we have made. 展开更多
关键词 Cosmological Vacuum Energy Energy Density Initial Time Step
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Cosmological constraints on ultra-light axion fields
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作者 Jian-Gang Kang Yan Gong +1 位作者 Gong Cheng Xuelei Chen 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2020年第4期99-106,共8页
Ultra-light axions(ULAs)with mass less than 10-20 eV have interesting behaviors that may contribute to either dark energy or dark matter at different epochs of the Universe.Their properties can be explored by cosmolog... Ultra-light axions(ULAs)with mass less than 10-20 eV have interesting behaviors that may contribute to either dark energy or dark matter at different epochs of the Universe.Their properties can be explored by cosmological observations,such as expansion history of the Universe,cosmic large-scale structure,cosmic microwave background,etc.In this work,we study the ULAs with mass around 10-33 eV,which means that the ULA field still rolls slowly at present with the equation of state w=-1 as dark energy.To investigate the mass and other properties of this kind of ULA field,we adopt the measurements of Type Ia supernova(SN Ia),baryon acoustic oscillation(BAO),and Hubble parameter H(z).The Markov Chain Monte Carlo(MCMC)technique is employed to perform the constraints on the parameters.Finally,by exploring four cases of the model,we find that the mass of this ULA field is about 3×10-33 eV if assuming the initial axion fieldφi=Mpl.We also investigate a general case by assumingφi≤Mpl,and find that the fitting results ofφi/Mpl are consistent with or close to 1 for the datasets that we use. 展开更多
关键词 COSMOLOGY DARK energy COSMOLOGICAL parameters
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