We investigated the scenario of time-dependent diffusive interaction between dark matter and dark energy and showed that such a model can be accommodated within the observations of luminosity distanceredshift data in ...We investigated the scenario of time-dependent diffusive interaction between dark matter and dark energy and showed that such a model can be accommodated within the observations of luminosity distanceredshift data in Supernova la(SN la)observations.We obtain constraints on different relevant parameters of this model from the observational data.We consider a homogeneous scalar field(t)driven by a k-essence Lagrangian of the form L=V(φ)F(X)with constant potential V(φ)=V,to describe the dynamics of dark energy in this model.Using the temporal behaviour of the FRW scale factor,the equation of state and total energy density of the dark fluid,extracted from the analysis of SN la(JLA)data,we have obtained the time-dependence of the k-essence scalar field and also reconstructed the form of the function F(X)in the k-essence Lagrangian.展开更多
In this study,we investigate the collapsing scenario for the k-essence emergent Vaidya spacetime in the context of massive gravity's rainbow.For this study,we consider that the background metric is Vaidya spacetim...In this study,we investigate the collapsing scenario for the k-essence emergent Vaidya spacetime in the context of massive gravity's rainbow.For this study,we consider that the background metric is Vaidya spacetime in massive gravity's rainbow.We show that the k-essence emergent gravity metric closely resembles the new type of generalized Vaidya massive gravity metric with the rainbow deformations for null fluid collapse,where we consider the k-essence scalar field as a function solely of the advanced or the retarded time.The k-essence emergent Vaidya massive gravity rainbow mass function is also different.This new type k-essence emergent Vaidya massive gravity rainbow metric satisfies the required energy conditions.The existence of a locally naked central singularity and the strength and strongness of the singularities for the rainbow deformations of the k-essence emergent Vaidya massive gravity metric are the interesting outcomes of the present work.展开更多
In this paper,we study the dynamics of k-essence in loop quantum cosmology(LQC).The study indicates that the loop quantum gravity(LQG)effect plays a key role only in the early epoch of the universe and is diluted in t...In this paper,we study the dynamics of k-essence in loop quantum cosmology(LQC).The study indicates that the loop quantum gravity(LQG)effect plays a key role only in the early epoch of the universe and is diluted in the later stages.The fixed points in LQC are basically consistent with those in standard Friedmann-Robertson-Walker(FRW)cosmology.For most of the attractor solutions,the stability conditions in L Q C are in agreement with those for the standard FRW universe.For some special fixed points,however,tighter constraints are imposed thanks to the LQG effect.展开更多
On studying some new models of Robertson-Walker universes with a Brans-Dicke scalar field, it is found that most of these universes contain a dark energy like fluid which confirms the present scenario of the expansion...On studying some new models of Robertson-Walker universes with a Brans-Dicke scalar field, it is found that most of these universes contain a dark energy like fluid which confirms the present scenario of the expansion of the universe. In one of the cases, the exact solution of the field equations gives a universe with a false vacuum, while in another it reduces to that of dust distribution in the Brans-Dicke cosmology when the cosmological constant is not in the picture. In one particular model it is found that the universe may undergo a Big Rip in the future, and thus it will be very interesting to investigate such models further.展开更多
The objective of this work is to generate a general formalism of f(R,L(X))-gravity in the context of dark energy under the framework of K-essence emergent geometry with the Dirac-Born-Infeld(DBI) variety of action,whe...The objective of this work is to generate a general formalism of f(R,L(X))-gravity in the context of dark energy under the framework of K-essence emergent geometry with the Dirac-Born-Infeld(DBI) variety of action,where R is the familiar Ricci scalar,L(X) is the DBI type non-canonical Lagrangian with X=1/2g^(μν)▽_(μ)φ▽_(ν)φ,and φ is the K-essence scalar field.The emergent gravity metric(G_(μν)) and the well known gravitational metric(g^(μν))are not conformally equivalent.We have constructed a modified field equation using the metric formalism in f(R,L(X))-gravity incorporating the corresponding Friedmann equations into the framework of the background gravitational metric,which is of Friedmann-Lemaitre-Robertson-Walker(FLRW) type.The solution of the modified Friedmann equations have been deduced for the specific choice of f(R,L(X)),which is of Starobinsky-type,using the power law expansion method.The consistency of the model with the accelerating phase of the universe has been shown when we restrict ourselves to consider the value of the dark energy density as φ^(2)=8/9=0.888 <1,which indicates that the present universe is dark-energy dominated.Graphical plots for the energy density(ρ),pressure(p),and equation of state parameter(ω) with respect to(w.r.t.) time(t) based on parametric values are interestingly consistent with the dark energy domination theory,and hence the accelerating features.We also highlight the corresponding energy conditions and constraints of the f(R,L(X)) theory with a basic example.展开更多
基金University Grants Commission(UGC),India for supporting this work by means of NET Fellowship(Ref.No.22/06/2014(i)EU-V and Sr.No.2061451168)。
文摘We investigated the scenario of time-dependent diffusive interaction between dark matter and dark energy and showed that such a model can be accommodated within the observations of luminosity distanceredshift data in Supernova la(SN la)observations.We obtain constraints on different relevant parameters of this model from the observational data.We consider a homogeneous scalar field(t)driven by a k-essence Lagrangian of the form L=V(φ)F(X)with constant potential V(φ)=V,to describe the dynamics of dark energy in this model.Using the temporal behaviour of the FRW scale factor,the equation of state and total energy density of the dark fluid,extracted from the analysis of SN la(JLA)data,we have obtained the time-dependence of the k-essence scalar field and also reconstructed the form of the function F(X)in the k-essence Lagrangian.
文摘In this study,we investigate the collapsing scenario for the k-essence emergent Vaidya spacetime in the context of massive gravity's rainbow.For this study,we consider that the background metric is Vaidya spacetime in massive gravity's rainbow.We show that the k-essence emergent gravity metric closely resembles the new type of generalized Vaidya massive gravity metric with the rainbow deformations for null fluid collapse,where we consider the k-essence scalar field as a function solely of the advanced or the retarded time.The k-essence emergent Vaidya massive gravity rainbow mass function is also different.This new type k-essence emergent Vaidya massive gravity rainbow metric satisfies the required energy conditions.The existence of a locally naked central singularity and the strength and strongness of the singularities for the rainbow deformations of the k-essence emergent Vaidya massive gravity metric are the interesting outcomes of the present work.
基金Supported by the Natural Science Foundation of China(11775036)Fok Ying Tung Education Foundation(171006)Jian-Pin Wu is also supported by Top Talent Support Program from Yangzhou University.
文摘In this paper,we study the dynamics of k-essence in loop quantum cosmology(LQC).The study indicates that the loop quantum gravity(LQG)effect plays a key role only in the early epoch of the universe and is diluted in the later stages.The fixed points in LQC are basically consistent with those in standard Friedmann-Robertson-Walker(FRW)cosmology.For most of the attractor solutions,the stability conditions in L Q C are in agreement with those for the standard FRW universe.For some special fixed points,however,tighter constraints are imposed thanks to the LQG effect.
文摘On studying some new models of Robertson-Walker universes with a Brans-Dicke scalar field, it is found that most of these universes contain a dark energy like fluid which confirms the present scenario of the expansion of the universe. In one of the cases, the exact solution of the field equations gives a universe with a false vacuum, while in another it reduces to that of dust distribution in the Brans-Dicke cosmology when the cosmological constant is not in the picture. In one particular model it is found that the universe may undergo a Big Rip in the future, and thus it will be very interesting to investigate such models further.
基金the DSTB,Government of West Bengal,India for financial support through the Grants No.:322(Sanc.)/ST/P/S&T/16G-3/2018 dated06.03.2019。
文摘The objective of this work is to generate a general formalism of f(R,L(X))-gravity in the context of dark energy under the framework of K-essence emergent geometry with the Dirac-Born-Infeld(DBI) variety of action,where R is the familiar Ricci scalar,L(X) is the DBI type non-canonical Lagrangian with X=1/2g^(μν)▽_(μ)φ▽_(ν)φ,and φ is the K-essence scalar field.The emergent gravity metric(G_(μν)) and the well known gravitational metric(g^(μν))are not conformally equivalent.We have constructed a modified field equation using the metric formalism in f(R,L(X))-gravity incorporating the corresponding Friedmann equations into the framework of the background gravitational metric,which is of Friedmann-Lemaitre-Robertson-Walker(FLRW) type.The solution of the modified Friedmann equations have been deduced for the specific choice of f(R,L(X)),which is of Starobinsky-type,using the power law expansion method.The consistency of the model with the accelerating phase of the universe has been shown when we restrict ourselves to consider the value of the dark energy density as φ^(2)=8/9=0.888 <1,which indicates that the present universe is dark-energy dominated.Graphical plots for the energy density(ρ),pressure(p),and equation of state parameter(ω) with respect to(w.r.t.) time(t) based on parametric values are interestingly consistent with the dark energy domination theory,and hence the accelerating features.We also highlight the corresponding energy conditions and constraints of the f(R,L(X)) theory with a basic example.