The universe content is considered as a non-perfect fluid with bulk viscosity and is described by a more general equation of state （endowed some deviation from the conventionally assumed cosmic perfect fluid model）....The universe content is considered as a non-perfect fluid with bulk viscosity and is described by a more general equation of state （endowed some deviation from the conventionally assumed cosmic perfect fluid model）. We assume the bulk viscosityis a linear combination of two terms： one is constant, and the other is proportional to the scalar expansion 0 = 3a/a. The equation of state is described as p = （γ - 1）p ＋ po, where po is a parameter. In this framework we demonstrate that this model can be used to explain the dark energy dominated universe, and different proper choices of the parameters may lead to three kinds of fates of the cosmological evolution： no future singularity, big rip, or Type-Ⅲ singularity as presented in IS. Nojiri, S.D. Odintsov, and S. Tsujikawa, Phys. Rev. D 71 （2005） 063004].展开更多
In order to study the effect of large scale cosmological expansion on small systems, we assume a Friedmann- Robertson-Walker type coordinate system in presence of a nonzero cosmological constant and derive a non-stati...In order to study the effect of large scale cosmological expansion on small systems, we assume a Friedmann- Robertson-Walker type coordinate system in presence of a nonzero cosmological constant and derive a non-static Reissner-Nrdstr6m metric. It is an analytic function of r for all values except at r = O, which is singular. By determining the equation of motion in this metric we can estimate how expansion of the universe may affect Pioneer＇s motion. Because the metric does not have any event horizon and so high potential regions are accessible, this may help us in better understanding AGN phenomenon.展开更多
A so-called ghost dark energy was recently proposed to explain the present acceleration of the universe.The energy density of ghost dark energy,which originates from Veneziano ghost of Quantum Chromodynamics(QCD),in a...A so-called ghost dark energy was recently proposed to explain the present acceleration of the universe.The energy density of ghost dark energy,which originates from Veneziano ghost of Quantum Chromodynamics(QCD),in a time dependent background,can be written in the form,ρD=αH + βH^2 where H is the Hubble parameter.We investigate the generalized ghost dark energy(GGDE) model in the setup of loop quantum Cosmology(LQC) and Galileon Cosmology.We study the cosmological implications of the models.We also obtain the equation of state and the deceleration parameters and differential equations governing the evolution of this dark energy model for LQC and Galileon Cosmology.展开更多
With the dark energy phenomena explored over a decade, in this present work we discuss a specific case of the generalized Einstein-aether theories, in which the modified Friedmann equation is similar to that in the Dv...With the dark energy phenomena explored over a decade, in this present work we discuss a specific case of the generalized Einstein-aether theories, in which the modified Friedmann equation is similar to that in the Dvali- Gabadadze-Porrati （DGP） brahe world model. We compute the joint statistic constraints on model parameters in this specific case by using the recent type Ia supernovae （SNe Ia） data, the cosmic microwave background （CMB） shift parameter data, and the baryonic acoustic oscillations （BAOs） data traced by the S1oan Digital Sky Survey （SDSS）. Furthermore, we analyze other constrains from the observational Hubble parameter data （OHD）. The comparison with the standard cosmological model （cosmological constant A cold dark matter （ACDM） model） is dearly shown; also we comment on the interesting relation between the coupling constant M in this model and the special accelerate scale in the modified Newtonian dynamies （MOND） model initially given by Milgrom with the hope for interpreting the galaxy rotation curves without introducing mysterious dark matter.展开更多
The paper shows how a generalization of the elasticity theory to four dimensions and to space-time allows for a consistent description of the homogeneous and isotropic universe,including the accelerated expansion.The ...The paper shows how a generalization of the elasticity theory to four dimensions and to space-time allows for a consistent description of the homogeneous and isotropic universe,including the accelerated expansion.The analogy is manifested by the inclusion in the traditional Lagrangian of general relativity of an additional term accounting for the strain induced in the manifold(i.e.in space-time)by the curvature,be it induced by the presence of a texture defect or by a matter/energy distribution.The additional term is su?cient to account for various observed features of the universe and to give a simple interpretation for the so called dark energy.Then,we show how the same approach can be adopted back in three dimensions to obtain the equilibrium configuration of a given solid subject to strain induced by defects or applied forces.Finally,it is shown how concepts coming from the familiar elasticity theory can inspire new approaches to cosmology and in return how methods appropriated to General Relativity can be applied back to classical problems of elastic deformations in three dimensions.展开更多
This issue of Science China Physics, Mechanics ＆ Astronomy celebrates the Centenary of Einstein＇s General Theory of Rela- tivity, which changed the way humanity understood the concepts of space, time and matter. Pri...This issue of Science China Physics, Mechanics ＆ Astronomy celebrates the Centenary of Einstein＇s General Theory of Rela- tivity, which changed the way humanity understood the concepts of space, time and matter. Prior to 1915 Einstein had intro- duced his theory of Special Relativity, and Minkowski had introduced the spacetime metric. General Relativity overthrew the Newtonian idea that space, time and matter were independent, replacing it with the idea that space, time and matter are inex- tricably linked. Within a year of the publication of General Relativity came Schwartzchild＇s exact solution of Einstein＇s field equations which describes the spacetime structure of black holes. In 1916 and 1918 Einstein showed that his theory predicted the existence of gravitational waves. Within 7 years, in 1922, Friedmann published a solution for Einstein＇s field equations applied to a homogeneous universe, uncovering the basic physics of Big Bang cosmology.展开更多
We discuss the P-V criticality and phase transition in the extended phase space of Born-Infeld AdS(BIAdS) black hole surrounded by quintessence dark energy, where the cosmological constant Λ is identified with the th...We discuss the P-V criticality and phase transition in the extended phase space of Born-Infeld AdS(BIAdS) black hole surrounded by quintessence dark energy, where the cosmological constant Λ is identified with the thermodynamical pressure P. Comparing with Van der Waals(VdW)-like SBH/LBH phase transition of Born-Infeld AdS(BI-AdS) black hole, we find that the BI-AdS black hole surrounded by quintessence dark energy possesses lower critical temperature because of parameter a > 0, even disappears since the parameter a taking enough large values leads to Tc ≤ 0. Moreover, the interesting thermodynamic phenomenon of reentrant phase transition(RPT) are also observed,and the quintessence dark energy plays a similar role in this RPT.展开更多
We investigate generalized chaplygin gas for warm inflationary scenario in the context of locally rotationally symmetric Bianchi type I universe model.We assume two different cases of dissipative coefficient,i.e.,cons...We investigate generalized chaplygin gas for warm inflationary scenario in the context of locally rotationally symmetric Bianchi type I universe model.We assume two different cases of dissipative coefficient,i.e.,constant as well as function of scalar field.We construct dynamical equations as well as a relationship between scalar and radiation energy densities under slow-roll approximation.We also derive slow-roll parameters,scalar and tensor power spectra,scalar spectral index,tensor to scalar ratio for analyzing inflationary background during high dissipative regime.We also use the WMAP7 data for the discussion of our parameters.展开更多
基金The project partly supported by National Natural Science Foundation of China under Grant No. 10675062 and the Doctoral Foundation of China We thank Profs. I. Brevik, S.D. 0dintsov, and Lewis H. Ryder for lots of interesting discussions.
文摘The universe content is considered as a non-perfect fluid with bulk viscosity and is described by a more general equation of state （endowed some deviation from the conventionally assumed cosmic perfect fluid model）. We assume the bulk viscosityis a linear combination of two terms： one is constant, and the other is proportional to the scalar expansion 0 = 3a/a. The equation of state is described as p = （γ - 1）p ＋ po, where po is a parameter. In this framework we demonstrate that this model can be used to explain the dark energy dominated universe, and different proper choices of the parameters may lead to three kinds of fates of the cosmological evolution： no future singularity, big rip, or Type-Ⅲ singularity as presented in IS. Nojiri, S.D. Odintsov, and S. Tsujikawa, Phys. Rev. D 71 （2005） 063004].
基金0ur thanks go to the Isfahan University of Technology for the financial support.
文摘In order to study the effect of large scale cosmological expansion on small systems, we assume a Friedmann- Robertson-Walker type coordinate system in presence of a nonzero cosmological constant and derive a non-static Reissner-Nrdstr6m metric. It is an analytic function of r for all values except at r = O, which is singular. By determining the equation of motion in this metric we can estimate how expansion of the universe may affect Pioneer＇s motion. Because the metric does not have any event horizon and so high potential regions are accessible, this may help us in better understanding AGN phenomenon.
文摘A so-called ghost dark energy was recently proposed to explain the present acceleration of the universe.The energy density of ghost dark energy,which originates from Veneziano ghost of Quantum Chromodynamics(QCD),in a time dependent background,can be written in the form,ρD=αH + βH^2 where H is the Hubble parameter.We investigate the generalized ghost dark energy(GGDE) model in the setup of loop quantum Cosmology(LQC) and Galileon Cosmology.We study the cosmological implications of the models.We also obtain the equation of state and the deceleration parameters and differential equations governing the evolution of this dark energy model for LQC and Galileon Cosmology.
基金Supported by Natural Science Foundation of China under Grant Nos. 11075078 and 10675062by the project of knowledge Innovation Program (PKIP) of Chinese Academy of Sciences (CAS) under Grant No. KJCX2.YW.W10 through the KITPC astrophysics and cosmology programmes where we have initiated this present work
文摘With the dark energy phenomena explored over a decade, in this present work we discuss a specific case of the generalized Einstein-aether theories, in which the modified Friedmann equation is similar to that in the Dvali- Gabadadze-Porrati （DGP） brahe world model. We compute the joint statistic constraints on model parameters in this specific case by using the recent type Ia supernovae （SNe Ia） data, the cosmic microwave background （CMB） shift parameter data, and the baryonic acoustic oscillations （BAOs） data traced by the S1oan Digital Sky Survey （SDSS）. Furthermore, we analyze other constrains from the observational Hubble parameter data （OHD）. The comparison with the standard cosmological model （cosmological constant A cold dark matter （ACDM） model） is dearly shown; also we comment on the interesting relation between the coupling constant M in this model and the special accelerate scale in the modified Newtonian dynamies （MOND） model initially given by Milgrom with the hope for interpreting the galaxy rotation curves without introducing mysterious dark matter.
文摘The paper shows how a generalization of the elasticity theory to four dimensions and to space-time allows for a consistent description of the homogeneous and isotropic universe,including the accelerated expansion.The analogy is manifested by the inclusion in the traditional Lagrangian of general relativity of an additional term accounting for the strain induced in the manifold(i.e.in space-time)by the curvature,be it induced by the presence of a texture defect or by a matter/energy distribution.The additional term is su?cient to account for various observed features of the universe and to give a simple interpretation for the so called dark energy.Then,we show how the same approach can be adopted back in three dimensions to obtain the equilibrium configuration of a given solid subject to strain induced by defects or applied forces.Finally,it is shown how concepts coming from the familiar elasticity theory can inspire new approaches to cosmology and in return how methods appropriated to General Relativity can be applied back to classical problems of elastic deformations in three dimensions.
文摘This issue of Science China Physics, Mechanics ＆ Astronomy celebrates the Centenary of Einstein＇s General Theory of Rela- tivity, which changed the way humanity understood the concepts of space, time and matter. Prior to 1915 Einstein had intro- duced his theory of Special Relativity, and Minkowski had introduced the spacetime metric. General Relativity overthrew the Newtonian idea that space, time and matter were independent, replacing it with the idea that space, time and matter are inex- tricably linked. Within a year of the publication of General Relativity came Schwartzchild＇s exact solution of Einstein＇s field equations which describes the spacetime structure of black holes. In 1916 and 1918 Einstein showed that his theory predicted the existence of gravitational waves. Within 7 years, in 1922, Friedmann published a solution for Einstein＇s field equations applied to a homogeneous universe, uncovering the basic physics of Big Bang cosmology.
基金Supported by the National Natural Science Foundation of China under Grant No.1160515Natural Science Foundation of Jiangsu Province under Grant No.BK20160452
文摘We discuss the P-V criticality and phase transition in the extended phase space of Born-Infeld AdS(BIAdS) black hole surrounded by quintessence dark energy, where the cosmological constant Λ is identified with the thermodynamical pressure P. Comparing with Van der Waals(VdW)-like SBH/LBH phase transition of Born-Infeld AdS(BI-AdS) black hole, we find that the BI-AdS black hole surrounded by quintessence dark energy possesses lower critical temperature because of parameter a > 0, even disappears since the parameter a taking enough large values leads to Tc ≤ 0. Moreover, the interesting thermodynamic phenomenon of reentrant phase transition(RPT) are also observed,and the quintessence dark energy plays a similar role in this RPT.
文摘We investigate generalized chaplygin gas for warm inflationary scenario in the context of locally rotationally symmetric Bianchi type I universe model.We assume two different cases of dissipative coefficient,i.e.,constant as well as function of scalar field.We construct dynamical equations as well as a relationship between scalar and radiation energy densities under slow-roll approximation.We also derive slow-roll parameters,scalar and tensor power spectra,scalar spectral index,tensor to scalar ratio for analyzing inflationary background during high dissipative regime.We also use the WMAP7 data for the discussion of our parameters.
