scholarly journals Dynamical description of a quintom cosmological model nonminimally coupled with gravity

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Mihai Marciu
Keyword(s):  
Dark Energy ◽  
Cosmological Model ◽  
Potential Energy ◽  
Space Structure ◽  
Point Of View ◽  
De Sitter ◽  
Phase Space Structure ◽  
Stability Method ◽  
Dynamical Properties ◽  
Dynamical Description

AbstractIn this work we have studied a cosmological model based on a quintom dark energy model non-minimally coupled with gravity, endowed with a specific potential energy of the exponential squared type. For this specific type of potential energy and non-minimal coupling, the dynamical properties are analyzed and the corresponding cosmological effects are discussed. Considering the linear stability method, we have investigated the dynamical properties of the phase space structure, determining the physically acceptable solutions. The analysis showed that in this model we can have various cosmological epochs, corresponding to radiation, matter domination, and de Sitter eras. Each solution is investigated from a physical and cosmological point of view, obtaining possible constraints of the model’s parameters. In principle the present cosmological setup represent a possible viable scalar tensor theory which can explain various transitional effects related to the behavior of the dark energy equation of state and the evolution of the Universe at large scales.

scholarly journals Applying explicit symplectic integrator to study chaos of charged particles around magnetized Kerr black hole

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
Wei Sun ◽  
Ying Wang ◽  
Fuyao Liu ◽  
Xin Wu
Keyword(s):  
Black Hole ◽  
Charged Particles ◽  
Kerr Black Hole ◽  
Space Structure ◽  
Point Of View ◽  
Symplectic Integrator ◽  
Spacetime Geometry ◽  
Kerr Spacetime ◽  
Phase Space Structure ◽  
Local Point

AbstractIn a recent work of Wu, Wang, Sun and Liu, a second-order explicit symplectic integrator was proposed for the integrable Kerr spacetime geometry. It is still suited for simulating the nonintegrable dynamics of charged particles moving around the Kerr black hole embedded in an external magnetic field. Its successful construction is due to the contribution of a time transformation. The algorithm exhibits a good long-term numerical performance in stable Hamiltonian errors and computational efficiency. As its application, the dynamics of order and chaos of charged particles is surveyed. In some circumstances, an increase of the dragging effects of the spacetime seems to weaken the extent of chaos from the global phase-space structure on Poincaré sections. However, an increase of the magnetic parameter strengthens the chaotic properties. On the other hand, fast Lyapunov indicators show that there is no universal rule for the dependence of the transition between different dynamical regimes on the black hole spin. The dragging effects of the spacetime do not always weaken the extent of chaos from a local point of view.

scholarly journals Phase Space Analysis of the Nonexistence of Dynamical Matching in a Stretched Caldera Potential Energy Surface

2019 ◽  
Vol 29 (04) ◽  
pp. 1950057 ◽  
Author(s):  
Matthaios Katsanikas ◽  
Stephen Wiggins
Keyword(s):  
Phase Space ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Critical Value ◽  
Space Structure ◽  
Space Structures ◽  
Two Dimensional ◽  
Phase Space Structure ◽  
Parametrized Family

In this paper, we continue our studies of the two-dimensional caldera potential energy surface in a parametrized family that allows for a study of the effect of symmetry on the phase space structures that govern how trajectories enter, cross, and exit the region of the caldera. As a particular form of trajectory crossing, we are able to determine the effect of symmetry and phase space structure on dynamical matching. We show that there is a critical value of the symmetry parameter which controls the phase space structures responsible for the manner of crossing, interacting with the central region (including trapping in this region) and exiting the caldera. We provide an explanation for the existence of this critical value in terms of the behavior of the Hénon stability parameter for the associated periodic orbits.

scholarly journals QUINTOM COSMOLOGY WITH GENERAL POTENTIALS

2009 ◽  
Vol 18 (04) ◽  
pp. 549-557 ◽  
Author(s):  
M. R. SETARE ◽  
E. N. SARIDAKIS
Keyword(s):  
Dark Energy ◽  
Phase Space ◽  
Dynamical Evolution ◽  
Space Structure ◽  
Late Time ◽  
Phase Space Structure ◽  
Phantom Model ◽  
Potential Form ◽  
Homogeneous Universe

We investigate the phase space structure of the quintom paradigm in the framework of a spatially flat, open or closed isotropic and homogeneous universe. We examine the dynamical evolution under the assumption of late time dark energy domination, without specifying the explicit quintom potential form. The obtained cosmological behavior is qualitatively different than that acquired from the single phantom model.

scholarly journals Cosmology in the mimetic higher-curvature $$f(R,R_{\mu \nu }R^{\mu \nu })$$ gravity

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Adam Z. Kaczmarek ◽  
Dominik Szczȩśniak
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Cosmological Model ◽  
Holographic Dark Energy ◽  
Scalar Potential ◽  
De Sitter ◽  
Field Equations ◽  
Dark Energy Density ◽  
Planck Data ◽  
Reconstruction Scheme

AbstractIn the framework of the mimetic approach, we study the $$f(R,R_{\mu \nu }R^{\mu \nu })$$ f ( R , R μ ν R μ ν ) gravity with the Lagrange multiplier constraint and the scalar potential. We introduce field equations for the discussed theory and overview their properties. By using the general reconstruction scheme we obtain the power law cosmology model for the $$f(R,R_{\mu \nu }R^{\mu \nu })=R+d(R_{\mu \nu }R^{\mu \nu })^p$$ f ( R , R μ ν R μ ν ) = R + d ( R μ ν R μ ν ) p case as well as the model that describes symmetric bounce. Moreover, we reconstruct model, unifying both matter dominated and accelerated phases, where ordinary matter is neglected. Using inverted reconstruction scheme we recover specific $$f(R,R_{\mu \nu }R^{\mu \nu })$$ f ( R , R μ ν R μ ν ) function which give rise to the de-Sitter evolution. Finally, by employing the perfect fluid approach, we demonstrate that this model can realize inflation consistent with the bounds coming from the BICEP2/Keck array and the Planck data. We also discuss the holographic dark energy density in terms of the presented $$f(R,R_{\mu \nu }R^{\mu \nu })$$ f ( R , R μ ν R μ ν ) theory. Thus, it is suggested that the introduced extension of the mimetic regime may describe any given cosmological model.

Cosmological spacetimes

2018 ◽  
Author(s):  
Nathalie Deruelle ◽  
Jean-Philippe Uzan
Keyword(s):  
Cosmological Model ◽  
Large Scale ◽  
Cosmic Time ◽  
De Sitter ◽  
Matter Distribution ◽  
Observable Universe ◽  
Cosmological Principle ◽  
Riemannian Spacetime ◽  
The Universe ◽  
Copernican Principle

This chapter provides a few examples of representations of the universe on a large scale—a first step in constructing a cosmological model. It first discusses the Copernican principle, which is an approximation/hypothesis about the matter distribution in the observable universe. The chapter then turns to the cosmological principle—a hypothesis about the geometry of the Riemannian spacetime representing the universe, which is assumed to be foliated by 3-spaces labeled by a cosmic time t which are homogeneous and isotropic, that is, ‘maximally symmetric’. After a discussion on maximally symmetric space, this chapter considers spacetimes with homogenous and isotropic sections. Finally, this chapter discusses Milne and de Sitter spacetimes.

Explicit symplectic-like integration with corrected map for inseparable Hamiltonian

2020 ◽  
Vol 501 (1) ◽  
pp. 1511-1519
Author(s):  
Junjie Luo ◽  
Weipeng Lin ◽  
Lili Yang
Keyword(s):  
Phase Space ◽  
Space Structure ◽  
Eighth Order ◽  
Time Step ◽  
Extended Phase ◽  
Energy Error ◽  
Phase Space Structure ◽  
Compact Binary ◽  
Three Body

ABSTRACT Symplectic algorithms are widely used for long-term integration of astrophysical problems. However, this technique can only be easily constructed for separable Hamiltonian, as preserving the phase-space structure. Recently, for inseparable Hamiltonian, the fourth-order extended phase-space explicit symplectic-like methods have been developed by using the Yoshida’s triple product with a mid-point map, where the algorithm is more effective, stable and also more accurate, compared with the sequent permutations of momenta and position coordinates, especially for some chaotic case. However, it has been found that, for the cases such as with chaotic orbits of spinning compact binary or circular restricted three-body system, it may cause secular drift in energy error and even more the computation break down. To solve this problem, we have made further improvement on the mid-point map with a momentum-scaling correction, which turns out to behave more stably in long-term evolution and have smaller energy error than previous methods. In particular, it could obtain a comparable phase-space distance as computing from the eighth-order Runge–Kutta method with the same time-step.

Anisotropic ghost dark energy cosmological model with hybrid expansion law

New Astronomy ◽  
2017 ◽  
Vol 57 ◽  
pp. 70-75 ◽  
Author(s):  
Chandra Rekha Mahanta ◽  
Nitin Sarma
Keyword(s):  
Dark Energy ◽  
Cosmological Model ◽  
Ghost Dark Energy

scholarly journals OBSERVATIONAL CONSTRAINTS ON THE GENERALIZED CHAPLYGIN GAS

2009 ◽  
Vol 18 (13) ◽  
pp. 2007-2022 ◽  
Author(s):  
SERGIO DEL CAMPO ◽  
J. R. VILLANUEVA
Keyword(s):  
Dark Energy ◽  
Cosmological Model ◽  
Chaplygin Gas ◽  
Observational Constraints ◽  
Energy Component ◽  
Generalized Chaplygin Gas ◽  
Astronomical Data ◽  
Astronomical Observations ◽  
Dark Energy Component ◽  
Two Parameters

In this paper we study a quintessence cosmological model in which the dark energy component is considered to be the generalized Chaplygin gas and the curvature of the three-geometry is taken into account. Two parameters characterize this sort of fluid: ν and α. We use different astronomical data for restricting these parameters. It is shown that the constraint ν ≲ α agrees well enough with the astronomical observations.

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