Universe evolution, as described by Friedmann's equations, is determined by source terms fixed by the choice of pressure $\times$ energy-density equations of state $p(ρ)$. The usual approach in Cosmology considers equations of state accounting only for kinematic terms, ignoring the contribution from the interactions between the particles constituting the source fluid. In this work the importance of these neglected terms is emphasized. A systematic method, based on the Statistical Mechanics of real fluids, is proposed to include them. A toy-model is presented which shows how such interaction terms can engender significant cosmological effects.
The dynamical behaviors of interacting dark energy in loop quantum cosmology are discussed in this paper. Based on defining three dimensionless variables, we simplify the equations of the fixed points. The fixed points for interacting dark energy can be determined by the Friedmann equation coupled with the dynamical equations {in Einstein cosmology}. But in loop quantum cosmology, besides the Friedmann equation, the conversation equation also give a constrain on the fixed points. The difference of stability properties for the fixed points in loop quantum cosmology and the ones in Einstein cosm…
We investigate interacting ghost dark energy models in higher dimensional cosmology. We attempt to model dark matter within a barotropic fluid with $P_{b}=ω(t)_{b}ρ$. In this work we consider four different models based on choosing equation of state parameter and interaction term. We confirm that our models agree with observational data.
It is showed that complex scalar fields with a self-interaction potential may propagate along null geodesics on flat Friedmann--Lemaître--Robertson--Walker universes with different time-dependent scale factors. This occurs provided they self interact adequately, for different forms of potentials, and even for the massive case.
In this paper we investigate the evolution of the viscous dark energy (DE) interacting with the dark matter (DM) in the Einstein cosmology model. Using the linearizing theory of the dynamical system, we find, in our model, there exists a stable late time scaling solution which corresponds to the accelerating universe, and we also find the unstable solution under some appropriate parameters. In order to alleviate the coincidence problem, some authors considered the effect of quantum correction due to the conform anomaly and the interacting dark energy model. But if we take into account the bulk…
We here investigate the model of interacting dark energy in the context of five dimensional brane cosmology. The effective equations of state of dark energy are evaluated for various choices of the variable time dependent cosmological constant. We have found that the interacting dark energy obeys the phantom divide/crossing scenario in this generalized model. It is also shown that interacting dark energy in this generalized model also resolves the cosmic coincidence problem.
We study the dynamics of interacting holographic dark energy model in Brans-Dicke cosmology for the future event horizon and the Hubble horizon cut-offs. We determine the system of first-order differential equations for the future event horizon and Hubble horizon cut-offs, and obtain the corresponding fixed points, attractors, repellers and saddle points. Finally, we investigate the cosmic coincidence problem in this model for the future event horizon and Hubble horizon cut-offs and find that for both cut-offs and for a variety of Brans-Dicke parameters the coincidence problem is almost resolv…
The present work deals with an interacting dark energy model in the framework of f(T) cosmology. A cosmologically viable form of f(T) is chosen (T is the torsion scalar in teleparallelism) in the background of flat homogeneous and isotropic Friedmann-Robertson-Walker (FRW) space-time model of the universe. The matter content of the universe is chosen as dust interacting with minimally coupled scalar field. The evolution equations are reduced to an autonomous system of ordinary differential equations by suitable transformation of variables. The nature of critical points are analyzed by evaluati…
We propose in this paper an interacting holographic dark energy (IHDE) model in chameleon--tachyon cosmology by interaction between the components of the dark sectors. In the formalism, the interaction term emerges from the scalar field coupling matter lagrangian in the model rather than being inserted into the formalism as an external source for the interaction. The correspondence between the tachyon field and the holographic dark energy (HDE) densities allows to reconstruct the tachyon scalar field and its potential in a flat FRW universe. The model can show the accelerated expansion of the …
This article examines the foundation of the recently developed relativistic variational formalism[1]. Our work is heavily based on [2, 27] which extends this approach to the multi-fluid theory and examines its utility in astrophysics and cosmology. Unlike the extension to the formalism mentioned above, that looks at the general interaction between different types of matter, we use the formalism to examine the interaction involving, ordinary matter, dark matter (DM) and dark energy (DE). We focus on entrainment phenomena involving the dark-sector constituents.
In this paper, we examine the interacting dark energy model in $f(T)$ cosmology. We assume dark energy as a perfect fluid and choose a specific cosmologically viable form $f(T)= β\sqrt{T} $. We show that there is one attractor solution to the dynamical equation of $f(T)$ Friedmann equations. Further we investigate the stability in phase space for a general $f(T)$ model with two interacting fluids. By studying the local stability near the critical points, we show that the critical points lie on the sheet $u^*=(c-1)v^*$ in the phase space, spanned by coordinates $(u,v,Ω,T)$. From this critical s…
The present work deals with the dynamical system investigation of interacting dark energy models (quintessence and phantom) in the framework of Loop Quantum Cosmology by taking into account a broad class of self-interacting scalar field potentials. The main reason for studying potentials beyond the exponential type is to obtain additional critical points which can yield more interesting cosmological solutions. The stability of critical points and the asymptotic behavior of the phase space are analyzed using dynamical system tools and numerical techniques. We study two class of interacting dark…
In this paper, we investigate the nature of self-interacting potential that can support the accelerated expansion of the universe as indicated by observational data. For this purpose, we consider the Bianchi type I (BI) universe model in the Brans-Dicke (BD) field scenario and use a power law for both the scalar field and the scale factor. It is found that the accelerated expansion of the universe can be discussed for a positive power law potential with negative values of the BD parameter. We also explore the evolution of energy density perturbations. This analysis indicates that the model all…
We investigate the interacting holographic dark energy (HDE) with Granda-Oliveros (GO) IR-cutoff in the framework of Brans-Dicke (BD) cosmology. We obtain the equation of state (EoS) parameter of HDE, $w_D$, the effective EoS parameter $w_{\mathrm{eff}}$, the deceleration parameter $q $ and the squared of sound speed $v_s^2$ in a flat FRW universe. We show that at late time the cosmic coincidence problem can be alleviated. Also we show that for non-interacting case, HDE can give a unified dark matter-dark energy profile in BD cosmology, except that it cannot solve the coincidence problem in th…
A proposal to study the effect of interaction in an agegraphic dark energy model in DGP brane-world cosmology is presented in this manuscript. After explaining the details, we proceed to apply the dynamical system approach to the model to analyze its stability. We first, constrain model parameters with a variety of independent observational data such as cosmic microwave background anisotropies, baryon acoustic oscillation peaks and observational Hubble data. Then, we obtain the critical points related to different cosmological epochs. In particular, we conclude that in the presence of interact…
We provide a detailed description for power-law scaling FRW cosmological models in Brans-Dicke theory dominated by two interacting fluid components during the expansion of the universe.
In this paper a possibility of the accelerated expansion of the large scale universe with a varying polytropic fluid of a certain type is presented. About a special role of non-gravitational interactions between dark energy and dark matter, in particular, about a possibility of improvement and solution of problems arising in modern cosmology, has been discussed for a long time. This motivates us to consider new models, where non-gravitational interactions between varying polytropic fluid and cold dark matter are allowed. Mainly non-linear interactions of a specific type is considered, found in…
The strange behaviour of the universe's dark sector offers us the flexibility to address cosmological problems with different approaches. Using this flexibility, we consider a possible exchange of energy among the dark sector components as a viable candidate model. In the present work, we investigate the interaction between two scalar fields within the generalization of a two-component chiral cosmology. We also show that there exists a unique equivalence between fields and fluids description of interacting dark sector model. Later, a detailed analysis of the dynamics of the dark energy-dark ma…
In this paper, we study an interacting holographic dark energy model in the framework of fractal cosmology. The features of fractal cosmology could pass ultraviolet divergencies and also make a better understanding of the universe in different dimensions. We discuss a fractal FRW universe filled with the dark energy and cold dark matter interacting with each other. It is observed that the Hubble parameter embraces the recent observational range while the deceleration parameter demonstrates an accelerating universe and a behavior similar to $Λ$CDM. Plotting the equation of state shows that it l…
In this work, we studied the Power Law and the Logarithmic Entropy Corrected versions of the Ricci Dark Energy (RDE) model in a spatially non-flat universe and in the framework of Hořava-Lifshitz cosmology. For the two cases containing non-interacting and interacting RDE and Dark Matter (DM), we obtained the exact differential equation that determines the evolutionary form of the RDE energy density parameter. Moreover, we obtained the expressions of the deceleration parameter $q$ and, using a parametrization of the equation of state (EoS) parameter $ω_D$ as $ω_D\left(z\right)=ω_0+ω_1 z$, we de…
We construct a cosmological model of late acceleration based on the new agegraphic dark energy model in the framework of Brans-Dicke cosmology where the new agegraphic energy density $ρ_{D}= 3n^2 m^2_p /η^{2}$ is replaced with $ρ_{D}= {3n^2ϕ^2}/({4ωη^2}$). We show that the combination of Brans-Dicke field and agegraphic dark energy can accommodate $w_D = -1 $ crossing for the equation of state of \textit{noninteracting} dark energy. When an interaction between dark energy and dark matter is taken into account, the transition of $w_D $ to phantom regime can be more easily accounted for than whe…
In this work we explore two possible scenarios that can be considered to extend a recent proposed model by the authors known as reconstructed mimetic cosmology. This study is complemented with an statistical analysis for each case. The first scenario considers the inclusion of matter production as a possible source of cosmic expansion in the reconstructed mimetic model, at effective level was found that this construction can cross the phantom divide, the model evolves from quintessence to phantom dark energy. The second scenario corresponds to a construction of an interacting scheme for the da…
This paper deals with a spatially homogeneous and totally anisotropic Bianchi type-V cosmological model within the framework of self interacting Brans Dicke theory of gravity in the background of anisotropic dark energy (DE) with variable equation of state (EoS) parameter and constant deceleration parameter. Constant deceleration parameter leads to two models of universe, i.e. power law model and exponential model. EoS parameter ω and its existing range for the models is in good agreement with the most recent observational data. We notice that ω given by (37) i.e ω(t) = log(k1t) is more suitab…
In this paper, we have studied the interacting and non-interacting dark energy and dark matter in the spatially homogenous and anisotropic Bianchi type-I model in the Brans- Dicke theory of gravitation. The field equations have been solved by using (i) power-law relation and (ii) by assuming scale factor in terms of redshift. Here we have considered two cases of an interacting and non-interacting dark energy scenario and obtained general results. It has been found that for suitable choice of interaction between dark energy and dark matter we can avoid the coincidence problem which appears in t…
In a spatially flat universe and for an interacting cosmology, we have reconstructed the interaction term, $Q$, between a cold dark matter (DM) fluid and a dark energy (DE) fluid, as well as a time-varying equation of state (EoS) parameter $\mathrm{ω_{DE}}$, and have explored their cosmological impacts on the amplitudes of the first six cosmographic parameters, which allow us to extract information about the kinematic state of the universe today. Here, both $Q$ and $\mathrm{ω_{DE}}$ have been modeled in terms of the Chebyshev polynomials. Then, via a Markov-Chain Monte Carlo (MCMC) method, we …
Classical and Loop Quantum Cosmology of Interacting Dark Energy: A Dynamical System Analysis with Superfluid Dark Matter and Dust Matter
Integral University（因蒂格拉尔大学）；L. N. Gumilyov Eurasian National University（列·尼·古米廖夫欧亚国立大学）；Symbiosis Institute of Technology, Nagpur Campus, Symbiosis International (Deemed University)（萨姆比亚斯理工学院那格浦尔校区，萨姆比亚斯国际（认定）大学）
We investigate Holographic Dark Energy Correspondence of Interacting Generalized Chaplygin Gas model in the framework of compact Kaluza-Klein cosmology. The evolution of the modified holographic dark energy and the equation of state parameter is obtained here.Using the present observational value of density parameter a stable configuration is formed which accommodates Dark Energy. we note a connection between Dark Energy and Phantom field and have shown that Dark Energy might have evolved from a Phantom state in the past.
The Noether Symmetry Approach is applied to interacting quintessence cosmology with the aim to search for exact solutions and select scalar-field self-interaction potentials. It turns out that the solutions found are compatible with the accelerated expansion of the Universe and with observational dataset, as the SNeIa Pantheon data.
We investigate the behavior of dark energy interacting with dark matter and unparticle in the framework of loop quantum cosmology. In four toy models, we study the interaction between the cosmic components by choosing different coupling functions representing the interaction. We found that there are only two attractor solutions namely dark energy dominated and dark matter dominated Universe. The other two models are unstable, as they predict either a dark energy filled Universe or one completely devoid of it.
We consider the cosmological dynamics of the cubic Galileon field model interacting with dark matter, where the interaction between the cosmic dark sectors is proportional to Hubble parameter and dark energy density. The background field equations are converted into an autonomous dynamical system of first order equations using suitable dimensionless variables. The fixed points are determined and their stability analyzed by means of the eigenvalue method. The analysis of the stability of the fixed points along that of the avoidance of ghosts and Laplacian instabilities implies negative coupling…
Reconstruction of f(G) Gravity from an Interacting Viscous Generalized QCD Ghost Dark Energy Model: Cosmology and Thermodynamics: Cosmology and Thermodynamics
Mukhtar Auezov South Kazakhstan University（穆赫塔尔·阿尤佐夫南哈萨克斯坦大学）；Amity University Kolkata（阿米提大学加尔各答分校）；L.N. Gumilyov Eurasian National University（L.N. 古米廖夫欧亚国立大学）
We investigate interacting dark energy models in the framework of fractal cosmology. We discuss a fractal FRW universe filled with the dark energy and dark matter which interact with each other. We obtain the equation for the relative density of dark matter and dark energy and the deceleration parameter. This model demonstrates new types of evolution, which are not common to cosmological models with this type of interaction.
Considering the holographic dark energy (HDE) with two different Infrared (IR) cutoffs, we study the evolution of a cyclic universe which avoids the Big-Rip singularity. Our results show that, even in the absence of a mutual interaction between the cosmos sectors, the HDE model with the Hubble radius as IR cutoff can mimics a cosmological constant in the framework of a cyclic cosmology. In addition, we find that both the interacting and non-interacting universes may enter into a cycle of sequential contraction and expansion, if the Granda-Oliveros (GO) cutoff is chosen as the IR cutoff in the …
In the framework of Brans-Dicke cosmology, we have studied the interacting power-law and logarithmic entropy-corrected holographic dark energy models with different cut-offs. The Brans-Dicke parameter is investigated versus the conditions for the acceleration and phantom phases to show that which entropy corrected model can exhibit acceleration with or without the phantom phase at early and present time universes. Moreover, the classical stability or instability of the interacting power-law and logarithmic entropy-corrected holographic dark energy models with different cut-offs is determined a…
In this paper, we study the holographic dark energy density and interacting extended Chaplygin gas energy density in the Einstein gravity. We reconstruct the scalar field and the scalar potential describing the extended Chaplygin gas. In the special case, we obtain energy density and investigate some cosmological parameters. Assuming interaction between components we find energy density for some different parametrization of total EoS. We analyze tensor to scalar ratio and use recent observational data of BICEP2 to fix the model parameters.
Rényi holographic dark energy (RHDE) correspondence is discussed in higher dimensional cosmology, namely Kaluza-Klein (KK) cosmology. Both interacting and non-interacting cosmological scenario are considered here. It is found that the non-interacting model naturally leads to the late accelerated universe, unlike the standard Holographic Dark Energy models in 4$D$, which requires interaction to accommodate the late-time acceleration of the universe. The interacting model produces an accelerating universe at late time albeit failing to attain the estimated present value of the deceleration param…
We study the entropy-corrected version of the holographic dark energy (HDE) model in the framework of modified FRW cosmology. We consider a non-flat universe filled with an interacting viscous entropy-corrected HDE (ECHDE) with dark matter. We also include the case of variable gravitational constant G in our model. We obtain the equation of state and the deceleration parameters of the interacting viscous ECHDE. Moreover, we reconstruct the potential and the dynamics of the quintessence, tachyon, K-essence and dilaton scalar field models according to the evolutionary behavior of the interacting…
The subject of our interest is an extended Chaplygin gas cosmology. In Literature a variety of cosmological models exist studying the behavior of the universe in the presence of the Chaplygin gas. From its initial form Chaplygin gas evolved and accepted different EoS-s and we will work with one of them. The main purpose of this work is to study behavior of the universe in Lyra Manifold with a varying Effective $Λ$-Term, which gives us modified field equations. We are also interested in the behavior of the universe in the case of an existing coupling between the quintessence DE and extended Cha…
Motivated by the recent work of one of us [1], we generalize this work to the case where the pressureless dark matter and the holographic dark energy do not conserve separately but interact with each other. We investigate the cosmological applications of interacting holographic dark energy in Brans-Dicke theory with chameleon scalar field which is non-minimally coupled to the matter field. We find out that in this model the phantom crossing can be constructed if the model parameters are chosen suitably. We also perform the study for the new agegraphic dark energy model and calculate some relev…
Using the Tsallis generalized entropy, holographic hypothesis and also considering the Hubble horizon as the IR cutoff, we build a holographic model for dark energy and study its cosmological consequences in the Brans-Dicke framework. At first, we focus on a non-interacting universe, and thereinafter, we study the results of considering a sign-changeable interaction between the dark sectors of the cosmos. Our investigations show that, compared with the flat case, the power and freedom of the model in describing the cosmic evolution is significantly increased in the presence of the curvature. T…
We investigate the cosmology of interacting spin-2 particles, formulating the multi-gravitational theory in terms of vierbeins and without imposing any Deser-van Nieuwenhuizen-like constraint. The resulting multi-vierbein theory represents a wider class of gravitational theories if compared to the corresponding multi-metric models. Moreover, as opposed to its metric counterpart which in general seems to contain ghosts, it has already been proved to be ghost-free. We outline a discussion about the possible matter couplings and we focus on the study of cosmological scenarios in the case of three…
We consider Brans-Dicke theory with a self-interacting potential in Einstein conformal frame. We show that an accelerating expansion is possible in a spatially flat universe for large values of the Brans-Dicke parameter consistent with local gravity experiments.
We discuss Tsallis holographic dark energy (THDE) model in higher dimension. An interacting dark energy model is proposed with Generalized Chaplygin Gas (GCG) in the framework of Compact Kaluza-Klein gravity. It is shown that a stable configuration can be found in the present epoch which is also compatible with the observed value of the density parameter. It is noted that dark energy (DE) might have evolved from a phantom phase in the past. Nature of dark energy is found to depend on the coupling parameter of the interaction. Classical stability consideration is also found to put an upper boun…
In this paper we study new cosmological models involving new forms of non-gravitational interaction between cold dark matter and dark energy. The main purpose is to demonstrate the applicability of the forms of interaction to the problem in modern cosmology known as accelerated expansion of the large scale universe. It is well known, that a non-gravitational interaction can improve theoretical prediction, but a fundamental theory allowing to derive the form of the interaction is missing. Therefore, an active sought to find a correct form of the interaction from various phenomenological assumpt…
We investigate the compact Kaluza-Klein cosmology in which modified holographic dark energy is interacting with dark matter. Using this scenario, we evaluate equation of state parameter as well as equation of evolution of the modified holographic dark energy. Further, it is shown that the generalized second law of thermodynamics holds without any constraint.
