Showing papers on "Deceleration parameter published in 2012"

Gaussian process cosmography

Abstract: Gaussian processes provide a method for extracting cosmological information from observations without assuming a cosmological model. We carry out cosmography---mapping the time evolution of the cosmic expansion---in a model-independent manner using kinematic variables and a geometric probe of cosmology. Using the state of the art supernova distance data from the Union2.1 compilation, we constrain, without any assumptions about dark energy parametrization or matter density, the Hubble parameter and deceleration parameter as a function of redshift. Extraction of these relations is tested successfully against models with features on various coherence scales, subject to certain statistical cautions.

From cosmic deceleration to acceleration: new constraints from SN Ia and BAO/CMB

Abstract: We use type Ia supernovae (SN Ia) data in combination with recent baryonic acoustic oscillations (BAO) and cosmic microwave background (CMB) observations to constrain a kink-like parametrization of the deceleration parameter (q). This q-parametrization can be written in terms of the initial (qi) and present (q0) values of the deceleration parameter, the redshift of the cosmic transition from deceleration to acceleration (zt) and the redshift width of such transition (τ). By assuming a flat space geometry, qi = 1/2 and adopting a likelihood approach to deal with the SN Ia data we obtain, at the 68% confidence level (C.L.), that: zt = 0.56+0.13−0.10, τ = 0.47+0.16−0.20 and q0 = −0.31+0.11−0.11 when we combine BAO/CMB observations with SN Ia data processed with the MLCS2k2 light-curve fitter. When in this combination we use the SALT2 fitter we get instead, at the same C.L.: zt = 0.64+0.13−0.07, τ = 0.36+0.11−0.17 and q0 = −0.53+0.17−0.13. Our results indicate, with a quite general and model independent approach, that MLCS2k2 favors Dvali-Gabadadze-Porrati-like cosmological models, while SALT2 favors ΛCDM-like ones. Progress in determining the transition redshift and/or the present value of the deceleration parameter depends crucially on solving the issue of the difference obtained when using these two light-curve fitters.

Cosmological models with linearly varying deceleration parameter

Abstract: We propose a new law for the deceleration parameter that varies linearly with time and covers Berman’s law where it is constant. Our law not only allows one to generalize many exact solutions that were obtained assuming constant deceleration parameter, but also gives a better fit with data (from SNIa, BAO and CMB), particularly concerning the late time behavior of the universe. According to our law only the spatially closed and flat universes are allowed; in both cases the cosmological fluid we obtain exhibits quintom like behavior and the universe ends with a big-rip. This is a result consistent with recent cosmological observations.

Direction dependence of the deceleration parameter

Abstract: In this paper we study the possibly existing anisotropy in the accelerating expansion Universe by use of the full sample of Union2 data. Using the hemisphere comparison method to search for a preferred direction, we take the deceleration parameter q(0) as the diagnostic to quantify the anisotropy level in the wCDM model. We find that the maximum accelerating expansion direction is (l,b) = (314(+20 degrees)(degrees-13 degrees),(degrees-33 degrees)(+11 degrees)), with the maximum anisotropy level of Delta q(0,max)/(q) over bar (0) = 0.79(+0.27)(-0.28),and that the anisotropy is more prominent when only low redshift data (z <= 0.2) are used. We also discuss this issue in the CPL parameterized model, showing a similar result.

Two-Fluid Scenario for Dark Energy Models in an FRW Universe-Revisited

Abstract: In this paper we study the evolution of the dark energy parameter within the scope of a spatially homogeneous and isotropic Friedmann-Robertson-Walker (FRW) model filled with barotropic fluid and dark energy by revisiting the recent results (Amirhashchi et al. in Chin. Phys. Lett. 28:039801, 2011a). To prevail the deterministic solution we select the scale factor $a(t) = \sqrt{t^{n}e^{t}}$ which generates a time-dependent deceleration parameter (DP), representing a model which generates a transition of the universe from the early decelerating phase to the recent accelerating phase. We consider the two cases of an interacting and non-interacting two-fluid (barotropic and dark energy) scenario and obtained general results. The cosmic jerk parameter in our derived model is also found to be in good agreement with the recent data of astrophysical observations under the suitable condition. The physical aspects of the models and the stability of the corresponding solutions are also discussed.

Three thermodynamically-based parameterizations of the deceleration parameter

Abstract: We propose and constrain with the latest observational data, three model-independent parametrizations of the cosmic deceleration parameter $q(z)$. They are well behaved and stay finite at all redshifts. We construct them by fixing the value of $q$ at high redshift, $q(z\ensuremath{\gg}1)=1/2$ (as demanded by cosmic structure formation), and at the far future $q(z=\ensuremath{-}1)=\ensuremath{-}1$, and smoothly interpolating $q(z)$ between them. The fixed point at $z=\ensuremath{-}1$ is not arbitrarily chosen; it readily follows from the second law of thermodynamics. This fairly reduces the ample latitude in parametrizing $q(z)$.

Observational constraints on Hubble constant and deceleration parameter in power-law cosmology

Abstract: In this paper, we show that the expansion history of the Universe in power-law cosmology essentially depends on two crucial parameters, namely the Hubble constant H0 and deceleration parameter q. We find the constraints on these parameters from the latest H(z) and SNe Ia data. At 1σ level the constraints from H(z) data are obtained as and km s−1 Mpc−1, while the constraints from the Type Ia supernovae (SNe Ia) data are and km s−1 Mpc−1. We also perform the joint test using H(z) and SNe Ia data, which yields the constraints and km s−1 Mpc−1. The estimates of H0 are found to be in close agreement with some recent probes carried out in the literature. The analysis reveals that the observational data successfully describe the cosmic acceleration within the framework of power-law cosmology. We find that the power-law cosmology accommodates well the H(z) and SNe Ia data. We also test the power-law cosmology using the primordial nucleosynthesis, which yields the constraints q≳ 0.72 and H0≲ 41.49 km s−1 Mpc−1. These constraints are found to be inconsistent with the ones derived from the H(z) and SNe Ia data. We carry out the statefinder analysis, and find that the power-law cosmological models approach the standard Λ cold dark matter (ΛCDM) model as q−1. Finally, we conclude that despite having several good features power-law cosmology is not a complete package for the cosmological purposes.

We do not live in the Rh = ct universe

Abstract: We analyse the possibility that our Universe could be described by the model recently proposed by Melia & Shevchuk (2012), where the Hubble scaleRh = c/H is at all times equal to the distance ct that light has travelled since the Big Bang. In such a model, the scale factor is proportional to cosmic time and there is neither acceleration nor decelerat ion of the expansion. We first point out problems with the very foundations of the model and its consequences for the evolution of the Universe. Next, we compare predictions of the model with observational data. As probes of the expansion we use distance data of supernovae type Ia, as well as Hubble rate data obtained from cosmic chronometers and radial baryon acoustic oscillatio ns. We analyse the redshift evolution of the Hubble parameter and its redshift derivatives, toget her with the so-called Om diagnostic and the deceleration parameter. To reliably estimate smoot h functions and their derivatives from discrete data, we use the recently developed Gaussian Processes in Python package (GaPP). Our general conclusion is that the discussed model is strongly d isfavoured by observations, especially at low redshifts (z . 0.5). In particular, it predicts specific constant values for th e deceleration parameter and for redshift derivatives of the Hubble parame ter, which is ruled out by the data.

Kaluza-Klein Cosmological Model in f(R,T) Gravity

Abstract: A five dimensional Kaluza-Klein space-time is considered in the presence of perfect fluid source in f(R,T) gravity proposed by Harko et al. ( arXiv:1104.2669 [gr-qc], 2011). A cosmological model with a negative constant deceleration parameter with an appropriate choice of a function f(T) is presented. To find a determinate solution of the field equations it is assumed that scalar of expansion is proportional to the shear scalar of the space time. The physical behavior of the model is also studied.

Cosmokinetics: A joint analysis of Standard Candles, Rulers and Cosmic Clocks

Abstract: We study the accelerated expansion of the Universe by using the kinematic approach. In this context, we parameterize the deceleration parameter, q(z), in a model independent way. Assuming three simple parameterizations we reconstruct q(z). We do the joint analysis with combination of latest cosmological data consisting of standard candles (Supernovae Union2 sample), standard ruler (CMB/BAO), cosmic clocks (age of passively evolving galaxies) and Hubble (H(z)) data. Our results support the accelerated expansion of the Universe.

Dark energy models with anisotropic fluid in Bianchi Type-VI (0) space-time with time dependent deceleration parameter

Abstract: We present two dark energy (DE) models with an anisotropic fluid in Bianchi type-VI 0 space-time by considering time dependent deceleration parameter (DP). The equation of state (EoS) for dark energy ω is found to be time dependent and its existing range for derived models is in good agreement with the recent observations. Under the suitable condition, the anisotropic models approach to isotropic scenario. We also find that during the evolution of the universe, the EoS parameter for DE changes from ω>−1 to ω=−1 in first model whereas from ω>−1 to ω<−1 in second model which is consistent with recent observations. The cosmological constant Λ 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 type Ia supernovae observations. The cosmic jerk parameter in our derived models is also found to be in good agreement with the recent data of astrophysical observations. The physical and geometric aspects of both the models are also discussed in detail.

High-redshift cosmography: new results and implications for dark energy

Abstract: The explanation of the accelerated expansion of the Universe poses one of the most fundamental questions in physics and cosmology today. If the acceleration is driven by some form of dark energy (DE), and in the absence of a well-based theory to interpret the observations, one can try to constrain the parameters describing the kinematical state of the universe using a cosmographic approach, which is fundamental in that it requires only a minimal set of assumptions, namely to specify the metric, and it does not rely on the dynamical equations for gravity. Our high-redshift analysis allows us to put constraints on the cosmographic expansion up to the fifth order. It is based on the Union2 type Ia Supernovae (SNIa) data set, the Hubble diagram constructed from some gamma ray burst luminosity distance indicators, and Gaussian priors on the distance from the baryon acoustic oscillations, and the Hubble constant h (these priors have been included in order to help break the degeneracies among model parameters). To perform our statistical analysis and to explore the probability distributions of the cosmographic parameters, we use the Markov Chain Monte Carlo method (MCMC). We finally investigate implications of our results for the DE; in particular, we focus on the parametrization of the DE equation of state (EOS). Actually, a possibility of investigating the nature of DE lies in measuring the DE EOS, w, and its time (or redshift) dependence at high accuracy. However, since w(z) is not directly accessible to measurement, reconstruction methods are needed to extract it reliably from observations. Here we investigate different models of DE, described through several parametrizations of the EOS, by comparing the cosmographic and the EOS series. The main results are as follows: (a) even if relying on a mathematical approximate assumption such as the scale factor series expansion in terms of time, cosmography can be extremely useful in assessing dynamical properties of the Universe; (b) the deceleration parameter clearly confirms the present acceleration phase; (c) the MCMC method provides stronger constraints for parameter estimation, in particular for higher order cosmographic parameters (the jerk and the snap), with respect to those presented in the literature; (d) both the estimation of the jerk and the DE parameters reflect the possibility of a deviation from the � CDM cosmological model; (e) there are indications that the DE EOS is evolving for all the parametrizations that we considered; (f) the q(z) reconstruction provided by our cosmographic analysis allows for a transient acceleration.

Effects of inhomogeneities on apparent cosmological observables: “fake” evolving dark energy

Abstract: Using the exact Lemaitre–Bondi–Tolman solution with a non-vanishing cosmological constant Λ, we investigate how the presence of a local spherically symmetric inhomogeneity can affect apparent cosmological observables, such as the deceleration parameter or the effective equation of state of dark energy (DE), derived from the luminosity distance under the assumption that the real space-time is exactly homogeneous and isotropic. The presence of a local underdensity is found to produce apparent phantom behavior of DE, while a locally overdense region leads to apparent quintessence behavior. We consider relatively small large scale inhomogeneities which today are not linear and could be seeded by primordial curvature perturbations compatible with CMB bounds. Our study shows how observations in an inhomogeneous ΛCDM universe with initial conditions compatible with the inflationary beginning, if interpreted under the wrong assumption of homogeneity, can lead to the wrong conclusion about the presence of “fake” evolving dark energy instead of Λ.

We do not live in the R_h = c t universe

Abstract: We analyse the possibility that our Universe could be described by the model recently proposed by Melia & Shevchuk (2012), where the Hubble scale R_h=c/H is at all times equal to the distance ct that light has travelled since the Big Bang. In such a model, the scale factor is proportional to cosmic time and there is neither acceleration nor deceleration of the expansion. We first point out problems with the very foundations of the model and its consequences for the evolution of the Universe. Next, we compare predictions of the model with observational data. As probes of the expansion we use distance data of supernovae type Ia, as well as Hubble rate data obtained from cosmic chronometers and radial baryon acoustic oscillations. We analyse the redshift evolution of the Hubble parameter and its redshift derivatives, together with the so-called O_m diagnostic and the deceleration parameter. To reliably estimate smooth functions and their derivatives from discrete data, we use the recently developed Gaussian Processes in Python package (GaPP). Our general conclusion is that the discussed model is strongly disfavoured by observations, especially at low redshifts (z<0.5). In particular, it predicts specific constant values for the deceleration parameter and for redshift derivatives of the Hubble parameter, which is ruled out by the data.

Interacting Ricci Dark Energy with Logarithmic Correction

Abstract: Motivated by the holographic principle, it has been suggested that the dark energy density may be inversely proportional to the area A of the event horizon of the universe. However, such a model would have a causality problem. In this work, we consider the entropy-corrected version of the holographic dark energy model in the non-flat FRW universe and we propose to replace the future event horizon area with the inverse of the Ricci scalar curvature. We obtain the equation of state (EoS) parameter ω Λ, the deceleration parameter q and $\Omega_{D}'$ in the presence of interaction between Dark Energy (DE) and Dark Matter (DM). Moreover, we reconstruct the potential and the dynamics of the tachyon, K-essence, dilaton and quintessence scalar field models according to the evolutionary behavior of the interacting entropy-corrected holographic dark energy model.

Accelerating Dark Energy Models in Bianchi Type-V Space-Time with Time Dependent Deceleration Parameter

Abstract: Some new exact solutions of Einstein's field equations have emerged in a spatially homogeneous and anisotropic Bianchi type-V space-time with minimally interacting perfect fluid and anisotropic dark energy (DE) components, which has dynamic equation of state (EoS). We consider Bianchi type-V space-time, introducing three different skewness parameters along spatial directions to quantify deviation of pressure from isotropy. To obtain the deterministic solution we choose the scale factor a(t )= √ t n e t , which yields a time-dependent deceleration parameter (DP). We find that the time dependent value of deceleration parameter is reasonable for the present day universe which yields a transition of the universe from the early decelerating phase to the recent accelerating phase. For different values of n, we can generate a class of physically viable DE models. It is found that quintessence model is suitable for describing the present evolution of the universe. The physical and geometric properties of spatially homogeneous and anisotropic cosmological models are discussed.

Dark energy model with variable q and ω in LRS Bianchi-II space-time

Abstract: The present study deals with spatial homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi-II dark energy model in general relativity. The Einstein’s field equations have been solved exactly by taking into account the proportionality relation between one of the components of shear scalar $(\sigma^{1}_{1})$ and expansion scalar (ϑ), which, for some suitable choices of problem parameters, yields time dependent equation of state (EoS) and deceleration parameter (DP), representing a model which generates a transition of universe from early decelerating phase to present accelerating phase. The physical and geometrical behavior of universe have been discussed in detail.

From cosmic deceleration to acceleration: new constraints from SN Ia and BAO/CMB

Abstract: We use type Ia supernovae (SN Ia) data in combination with recent baryonic acoustic oscillations (BAO) and cosmic microwave background (CMB) observations to constrain a kink-like parametrization of the deceleration parameter ($q$). This $q$-parametrization can be written in terms of the initial ($q_i$) and present ($q_0$) values of the deceleration parameter, the redshift of the cosmic transition from deceleration to acceleration ($z_t$) and the redshift width of such transition ($\tau$). By assuming a flat space geometry, $q_i=1/2$ and adopting a likelihood approach to deal with the SN Ia data we obtain, at the 68% confidence level (C.L.), that: $z_t=0.56^{+0.13}_{-0.10}$, $\tau=0.47^{+0.16}_{-0.20}$ and $q_0=-0.31^{+0.11}_{-0.11}$ when we combine BAO/CMB observations with SN Ia data processed with the MLCS2k2 light-curve fitter. When in this combination we use the SALT2 fitter we get instead, at the same C.L.: $z_t=0.64^{+0.13}_{-0.07}$, $\tau=0.36^{+0.11}_{-0.17}$ and $q_0=-0.53^{+0.17}_{-0.13}$. Our results indicate, with a quite general and model independent approach, that MLCS2k2 favors Dvali-Gabadadze-Porrati-like cosmological models, while SALT2 favors $\Lambda$CDM-like ones. Progress in determining the transition redshift and/or the present value of the deceleration parameter depends crucially on solving the issue of the difference obtained when using these two light-curve fitters.

String cosmological models from early deceleration to current acceleration phase with varying G and $ \Lambda$

Abstract: Thepresent study deals with spatially homogeneous and anisotropic Bianchi-I cosmological models representing massive strings with variable G and decaying vacuum energy density \( \Lambda\) . The energy-momentum tensor, as formulated by Letelier (Phys. Rev. D 20, 1294 (1979); Phys. Rev. D 28, 2414 (1983)), has been used to construct massive string cosmological models for which we assume the expansion scalar in the models is proportional to one of the components of shear tensor and barotropic EoS. The Einstein field equations have been solved by considering the time-dependent deceleration parameter which yields a scale factor \( a(t) = (\sinh(\alpha t))^{\frac{1}{n}}\) , where n is a positive constant. For n > 1 , this generates a transition of the Universe from the early decelerating phase to the recent accelerating phase and the transition redshift zt has been calculated. The study reveals that massive strings dominate the early Universe evolving with deceleration and in the later phase they disappear, which is in good agreement with current astronomical observations. The cosmological constant \( \Lambda\) is found to be a positive decreasing function of time which is corroborated by results from recent Supernovae Ia observations. The physical and geometric properties of the models have been also discussed in detail.

Bianchi Type-V Dark Energy Model in a Scalar-Tensor Theory of Gravitation

Abstract: A spatially homogeneous and anisotropic Bianchi type-V universe with variable equation of state (EoS) parameter and constant deceleration parameter is obtained in a scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, 1986). The physical and kinematical properties of the universe have been discussed.

A dark energy model in a scalar tensor theory of gravitation

Abstract: LRS Bianchi type-I dark energy model with variable equation of state (EoS) parameter is presented in the scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, 1986). To get a determinate solution of the field equations we take the help of special law of variation for Hubble’s parameter presented by Bermann (Nuovo Cimento B 74:182, 1983) which yields a cosmological model with negative constant deceleration parameter. Some physical and kinematical properties of the model are also discussed.

Cosmologies in Horndeski's second-order vector-tensor theory

Abstract: Horndeski derived a most general vector-tensor theory in which the vector field respects the gauge symmetry and the resulting dynamical equations are of second order. The action contains only one free parameter, $\lambda$, that determines the strength of the non-minimal coupling between the gauge field and gravity. We investigate the cosmological consequences of this action and discuss observational constraints. For $\lambda<0$ we identify singularities where the deceleration parameter diverges within a finite proper time. This effectively rules out any sensible cosmological application of the theory for a negative non-minimal coupling. We also find a range of parameter that gives a viable cosmology and study the phenomenology for this case. Observational constraints on the value of the coupling are rather weak since the interaction is higher-order in space-time curvature.

Nonsingular Brans-Dicke- Λ cosmology

Abstract: We discuss a Brans-Dicke model with a cosmological constant, a negative value of the $w$ parameter, and an arbitrary (in general nonvanishing) scale factor at the big bang. The Friedmann equations for a flat universe are considered. The current observational values for Hubble constant ${H}_{0}$ and deceleration parameter ${q}_{0}$ play the role of initial conditions. We follow the approach of Uehara and Kim in order to solve field equations analytically. In K. Uehara and C. W. Kim [Phys. Rev. D 26, 2575 (1982)] only positive values of $w$ were considered; we extend the study to a complete set of possible $w$ values. Our main result is that the scale factor (during its evolution back in time direction) may not vanish, unlike in the standard $\ensuremath{\Lambda}\mathrm{CDM}$ case. In other words, the considered model demonstrates a cosmological bounce instead of the initial singularity. The famous formula (24), that leads to the bounce, is valid only for the dust-filled universe with $p=0$ and, therefore, is not adequate for the early universe hot stage when the bounce happens. So, our results are qualitative in nature and must be used to obtain initial values for the hot stage of the Universe.

Accelerating dark energy models with anisotropic fluid in Bianchi type-$VI_{0}$ space-time

Abstract: Motivated by the increasing evidence for the need of a geometry that resembles Bianchi morphology to explain the observed anisotropy in the WMAP data, we have discussed some features of the Bianchi type-$VI_{0}$ universes in the presence of a fluid that wields 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-$VI_{0}$ space-time. To prevail the deterministic solution we choose the scale factor $a(t) = \sqrt{t^{n}e^{t}}$, which yields a time-dependent deceleration parameter (DP), representing a class of models which generate a transition of the universe from the early decelerating phase to the recent accelerating phase. Under the suitable condition, the anisotropic models approach to isotropic scenario. The EoS for dark energy $\omega$ is found to be time-dependent and its existing range for derived models is in good agreement with the recent observations of SNe Ia data (Knop et al. 2003), SNe Ia data with CMBR anisotropy and galaxy clustering statistics (Tegmark et al. 2004) and latest combination of cosmological datasets coming from CMB anisotropies, luminosity distances of high redshift type Ia supernovae and galaxy clustering (Hinshaw et al. 2009; Komatsu et al. 2009). For different values of $n$, we can generate a class of physically viable DE models.The cosmological constant $\Lambda$ is found to be a positive decreasing function of time and it approaches to a small positive value at late time (i.e. the present epoch) which is corroborated by results from recent type Ia supernovae observations. We also observe that our solutions are stable. The physical and geometric aspects of both the models are also discussed in detail.

QCD ghost f(T)-gravity model

Abstract: Within the framework of modified teleparallel gravity, we reconstruct a f(T) model corresponding to the QCD ghost dark energy scenario. For a spatially flat FRW universe containing only the pressureless matter, we obtain the time evolution of the torsion scalar T (or the Hubble parameter). Then, we calculate the effective torsion equation of state parameter of the QCD ghost f(T)-gravity model as well as the deceleration parameter of the universe. Furthermore, we fit the model parameters by using the latest observational data including SNeIa, CMB and BAO data. We also check the viability of our model using a cosmographic analysis approach. Moreover, we investigate the validity of the generalized second law (GSL) of gravitational thermodynamics for our model. Finally, we point out the growth rate of matter density perturbation. We conclude that in QCD ghost f(T)-gravity model, the universe begins a matter dominated phase and approaches a de Sitter regime at late times, as expected. Also this model is consistent with current data, passes the cosmographic test, satisfies the GSL and fits the data of the growth factor well as the LCDM model.

LRS Bianchi type-II dark energy model in a scalar–tensor theory of gravitation

Abstract: A locally rotationally symmetric Bianchi type-II (LRS B-II) space-time with variable equation of state (EoS) parameter and constant deceleration parameter have been investigated in the scalar-tensor theory proposed by Saez and Ballester (Phys. Lett. A 113:467, 1986). The scalar-tensor field equations have been solved by applying variation law for generalized Hubble’s parameter given by Bermann (Nuovo Cimento 74:182, 1983). The physical and kinematical properties of the model are also discussed.

Bianchi—V string cosmological model and late time acceleration

Abstract: We have searched for the existence of the late time acceleration of the universe with string fluid as the source of matter in Bianchi—V space-time. To derive a deterministic solution, we choose the scale factor to be an increasing function of time that yields a time dependent deceleration parameter, representing a model which generates a universe showing a transition from an early decelerating phase to a recent accelerating phase. The study reveals that strings dominate the early universe and eventually disappear from the universe for sufficiently large times, i.e. in the present epoch. This picture is consistent with current astronomical observations. The physical behavior of the universe is discussed in detail.

Power-law entropy-corrected ricci dark energy and dynamics of scalar fields

Abstract: Motivated by the holographic principle, it has previously been suggested that the dark energy (DE) density can be inversely proportional to the area A of the event horizon of the Universe. However, this kind of model would have a casuality problem. In this work, we study the power-law entropy-corrected holographic DE (PLECHDE) model in the non-flat Friedmann?Robertson?Walker universe, with the future event horizon replaced by the average radius of the Ricci scalar curvature. We derive the equation of state parameter ??, the deceleration parameter q and the evolution of energy density parameter ?D? in the presence of interaction between DE and dark matter. We consider the correspondence between our Ricci-PLECHDE model and the modified Chaplygin gas and the tachyon, K-essence, dilaton and quintessence scalar fields. The potential and dynamics of the scalar field models have been reconstructed according to the evolutionary behaviour of the interacting entropy-corrected holographic DE model.

Power-Law Entropy Corrected Ricci Dark Energy and Dynamics of Scalar Fields

Abstract: Motivated by the holographic principle, it has been suggested that the Dark Energy (DE) density can be inversely proportional to the area $A$ of the event horizon of the universe. However, this kind of model would have a casuality problem. In this work, we study the power-law entropy corrected holographic DE (PLECHDE) model in the non-flat Friedmann-Robertson-Walker universe, with the future event horizon replaced by the average radius of the Ricci scalar curvature. We derive the equation of state parameter $\omega_{\Lambda}$, the deceleration parameter $q$ and the evolution of energy density parameter $\Omega_D'$ in presence of interaction between DE and Dark Matter (DM). We consider the correspondence between our Ricci-PLECHDE model and the Modified Chaplygin Gas (MCG) and the tachyon, K-essence, dilaton and quintessence scalar fields. The potential and the dynamics of the scalar field models have been reconstructed according to the evolutionary behaviour of the interacting entropy-corrected holographic DE model.

Reconstruction of modified gravity with ghost dark energy models

Abstract: In this work, we reconstruct the f(R) modified gravity for different ghost and generalized-ghost dark energy (DE) models in FRW flat universe, which describes the accelerated expansion of the universe. The equation of state and deceleration parameter of reconstructed f(R) gravity have been calculated. The equation of state and deceleration parameter of reconstructed f(R)-ghost/generalized-ghost DE, have been calculated. We show that the corresponding f(R) gravity of ghost/generalized-ghost DE model can behave like phantom or quintessence. Also the transition between deceleration to acceleration regime is indicated by deceleration parameter diagram for reconstructed f(R) generalized-ghost DE model.