A varying polytropic gas universe and phase space analysis

2016 ◽  
Vol 31 (16) ◽  
pp. 1650097 ◽  
Author(s):  
M. Khurshudyan
Keyword(s):  
Phase Space ◽  
Large Scale ◽  
Accelerated Expansion ◽  
Late Time ◽  
Mathematical Tool ◽  
Phase Space Analysis ◽  
Space Analysis ◽  
Polytropic Gas ◽  
Dark Fluid ◽  
Large Scale Universe

In this paper, we will consider a phenomenological model of a dark fluid that is able to explain an accelerated expansion of our low redshift universe and the phase transition to this accelerated expanding universe. Recent developments in modern cosmology towards understanding of the accelerated expansion of the large scale universe involve various scenarios and approaches. Among these approaches, one of well-known and accepted practice is modeling of the content of our universe via dark fluid. There are various models of dark energy fluid actively studied in recent literature and polytropic gas is among them. In this work, we will consider a varying polytropic gas which is a phenomenological modification of polytropic gas. Our model of varying polytropic dark fluid has been constructed to analogue to a varying Chaplygin gas actively discussed in the literature. We will consider interacting models, where dark matter is a pressureless fluid, to have a comprehensive picture. Phase space analysis is an elegant mathematical tool to earn general understanding of large scale universe and easily see an existence of a solution to cosmological coincidence problem. Imposing some constraints on parameters of the models, we found late time attractors for each case analytically. Cosmological consequences for the obtained late time attractors are discussed.

Phase space analysis of the Umami Chaplygin model

2021 ◽  
pp. 2150052
Author(s):  
Qihong Huang ◽  
Ruanjing Zhang ◽  
Jun Chen ◽  
He Huang ◽  
Feiquan Tu
Keyword(s):  
Phase Space ◽  
Cosmic Acceleration ◽  
Accelerated Expansion ◽  
Late Time ◽  
Phase Space Analysis ◽  
Space Analysis ◽  
History Of ◽  
Evolutionary Trajectories ◽  
The Universe ◽  
Universe Evolution

In this paper, we analyze the universe evolution and phase space behavior of the Umami Chaplygin model, where the Umami Chaplygin fluid replaces both a dark energy and a dark and baryonic matter. We find the Umami Chaplygin model can be stable against perturbations under some conditions and can be used to explain the late-time cosmic acceleration. The results of phase space analysis show that there exists a late-time accelerated expansion attractor with [Formula: see text], which indicates the Umami Chaplygin fluid can behave as a cosmological constant. Moreover, the Umami Chaplygin model can describe the expansion history of the universe. The evolutionary trajectories of the statefinder diagnostic pairs and the finite time future singularities are also discussed.

Phase space analysis in a model of f(T) gravity with nonlinear sign changeable interactions

2017 ◽  
Vol 14 (03) ◽  
pp. 1750041 ◽  
Author(s):  
Martiros Khurshudyan
Keyword(s):  
Phase Space ◽  
Modified Gravity ◽  
Large Scale ◽  
Nonlinear Interactions ◽  
Phase Space Analysis ◽  
Space Analysis ◽  
Recent Interest ◽  
Modern Cosmology ◽  
Large Scale Universe ◽  
The Universe

Sign changeable interactions continue to gain serious attention in modern cosmology. On the other hand, recent interest towards nonlinear interactions gave us a motivation to consider various sign changeable nonlinear interactions. In this paper, we will consider cosmological models involving suggested new sign changeable nonlinear interactions. To describe background dynamics of the large scale universe [Formula: see text] gravity is used i.e the universe is governed by torsional modified gravity. In our models, we adopted barotropic EoS and pressureless fluid to model dark energy and dark matter, respectively. In addition to other assumptions about the models, particular form of [Formula: see text] is considered to perform phase space analysis.

scholarly journals A NOTE ON THE COSMOLOGICAL DYNAMICS IN FINITE-RANGE GRAVITY

2003 ◽  
Vol 12 (04) ◽  
pp. 689-696 ◽  
Author(s):  
M. SAMI
Keyword(s):  
Phase Space ◽  
Gravity Theory ◽  
Accelerated Expansion ◽  
Late Time ◽  
Finite Range ◽  
Phase Space Analysis ◽  
Space Analysis ◽  
Late Time Acceleration ◽  
Isotropic Cosmology ◽  
The Universe

In this note we consider the homogeneous and isotropic cosmology in the finite-range gravity theory recently proposed by Babak and Grishchuk. In this scenario the universe undergoes late time accelerated expansion if both the massive gravitons present in the model are tachyons. We carry out the phase space analysis of the system and show that the late-time acceleration is an attractor of the model.

Interacting dark energy models in f(T) gravity

2017 ◽  
Vol 32 (18) ◽  
pp. 1750097 ◽  
Author(s):  
M. Khurshudyan ◽  
R. Myrzakulov ◽  
As. Khurshudyan
Keyword(s):  
Phase Transition ◽  
Observational Data ◽  
Large Scale ◽  
Cosmological Models ◽  
Accelerated Expansion ◽  
Late Time ◽  
Time Behavior ◽  
Expanding Universe ◽  
Theory Of Gravity ◽  
Large Scale Universe

The accelerated expansion of the large-scale universe can be explained in various ways. There are various modifications, and each of them makes an attempt to give its own explanation of the physics behind it. It is well known that modern cosmology is full of various phenomenological assumptions to obtain comprehensive results comparable with observational data. General Relativity is the main theory of gravity and proposed modifications compared to it, giving a hope to find explanations of phenomenological assumptions. f(T) theory of gravity is one of the options. In this paper, we will consider a particular example of f(T) theory and study the effects of various interactions on a cosmological model. Phase space analysis is used to have a qualitative understanding of the late-time behavior of the suggested cosmological models. During our study, we found that among phenomenological models suggested in this paper, we have cosmological models being in good agreement with the observational data. Moreover, study of the behavior of the deceleration parameter q showed a phase transition from a decelerated expanding universe to the accelerated (recent) expanding universe. On the other hand, for the parameters of the models giving the mentioned phase transition, we have estimated the present day values of statefinder parameters (r, s).

scholarly journals Phase space analysis of a FRW cosmology in the Maxwell–Cattaneo approach

2018 ◽  
Vol 27 (16) ◽  
pp. 1950001 ◽  
Author(s):  
Yoelsy Leyva
Keyword(s):  
Dark Matter ◽  
Phase Space ◽  
Bulk Viscosity ◽  
Early Time ◽  
Late Time ◽  
Stiff Matter ◽  
Phase Space Analysis ◽  
Space Analysis ◽  
Perfect Fluids ◽  
Frw Model

In this work, we present a phase space analysis of a spatially flat Friedmann–Robertson–Walker (FRW) model in which the dark matter fluid is modeled as an imperfect fluid having bulk viscosity. The bulk viscosity is governed by the Maxwell–Cattaneo approach. The rest of the components of the model — radiation and dark energy — are treated as perfect fluids. Imposing a complete cosmological dynamics and taking into account a recent constraint on the dark matter equation-of-state (EOS), we obtain bound on the bulk viscosity. We show that is possible to describe transitions from radiation-dominated to matter-dominated period, which then evolves to a stable accelerated solution of late time. At early time, before the radiation-dominated epoch, the model suggests the presence of an unstable stiff matter solution which is not possible to associate with a viable configuration in the early universe.

scholarly journals Dynamics of Mixed Dark Energy Domination in Teleparallel Gravity and Phase-Space Analysis

2015 ◽  
Vol 2015 ◽  
pp. 1-20 ◽  
Author(s):  
Emre Dil ◽  
Erdinç Kolay
Keyword(s):  
Dark Energy ◽  
Phase Space ◽  
Scalar Fields ◽  
Teleparallel Gravity ◽  
Late Time ◽  
Baryonic Matter ◽  
Acceleration Phase ◽  
Phase Space Analysis ◽  
Space Analysis ◽  
Phantom Scalar

We consider a novel dark energy model to investigate whether it will provide an expanding universe phase. Here we propose a mixed dark energy domination which is constituted by tachyon, quintessence, and phantom scalar fields nonminimally coupled to gravity, in the absence of background dark matter and baryonic matter, in the framework of teleparallel gravity. We perform the phase-space analysis of the model by numerical methods and find the late-time accelerated attractor solutions implying the acceleration phase of universe.

Phase-space analysis of daily streamflow: characterization and prediction

1998 ◽  
Vol 21 (6) ◽  
pp. 463-475 ◽  
Author(s):  
Q. Liu ◽  
S. Islam ◽  
I. Rodriguez-Iturbe ◽  
Y. Le
Keyword(s):  
Phase Space ◽  
Phase Space Analysis ◽  
Space Analysis ◽  
Daily Streamflow
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