Article
Astronomy & Astrophysics
Genly Leon, Felipe Orlando Franz Silva
Summary: In this study, local and global phase-space descriptions and averaging methods were used to investigate the qualitative features of solutions for FLRW and Bianchi I metrics in the context of scalar field cosmologies with arbitrary potentials and couplings to matter. Equilibrium points representing various cosmological solutions such as scaling solutions, kinetic-dominated solutions, and vacuum de Sitter solutions associated with the minimum of the potential were obtained, revealing a rich cosmological phenomenology.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Astronomy & Astrophysics
Artur Alho, Woei Chet Lim, Claes Uggla
Summary: In this study, we use a dynamical systems formulation to analyze models with an exponential scalar field and matter with a linear equation of state in a spatially flat and isotropic spacetime. Unlike previous work, which only focused on linear hyperbolic fixed point analysis, we conduct a center manifold analysis of the non-hyperbolic fixed points associated with bifurcations. Additionally, we construct monotonic functions and a Dulac function. By combining these findings with a complete local fixed point analysis, we provide proofs that describe the entire global dynamics of these models, enhancing the previous local results in the literature.
CLASSICAL AND QUANTUM GRAVITY
(2022)
Article
Astronomy & Astrophysics
G. Papagiannopoulos, Spyros Basilakos, Emmanuel N. Saridakis
Summary: In this study, we analyze the dynamical system of Myrzakulov or F(R, T) gravity, focusing on its subclasses and their critical points. We examine the stability and physical features of these models. Our findings show that in class 1 models, the Universe will result in a dark-energy-dominated critical point, while in class 2 models, the behavior of dark energy can be more varied.
Article
Physics, Particles & Fields
Christian G. Bohmer, Erik Jensko, Ruth Lazkoz
Summary: When considering a homogeneous and isotropic cosmological model, the field equations of modified gravity theories can be transformed into autonomous differential equations, which is a successful approach to study such models. We propose a perspective that is applicable to many different modified gravity models and relies on the standard cosmological density parameters, allowing for the extraction of generic information before considering a specific model.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Particles & Fields
S. A. Kadam, B. Mishra, Jackson Levi Said
Summary: This work investigates the impact of a nontrivial input from the kinetic term of the scalar field in scalar-tensor theories in the context of teleparallel gravity. The study reveals the evolutionary behavior of these systems by considering various model settings and determining their critical points. The dynamics of the systems are also discussed.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Mathematics
Genly Leon, Alfredo D. Millano, Andronikos Paliathanasis
Summary: In this study, we investigate the phase space of a scalar field theory obtained through minisuperspace deformation. We consider quintessence or phantom scalar fields in the action derived from minisuperspace deformation on the Einstein-Hilbert action. Our analysis utilizes a modified Poisson algebra with alpha-deformed Poisson brackets that are linked to the Moyal-Weyl star product. We discuss both early- and late-time attractors and reconstruct the cosmological evolution. Additionally, we demonstrate that the model can exhibit the lambda CDM model as a future attractor if we start with a massless scalar field without a cosmological constant term.
Article
Multidisciplinary Sciences
Rodrigo R. Cuzinatto, Rajendra P. Gupta, Pedro J. Pompeia
Summary: In this study, a scalar-tensor theory of gravity is investigated, where the gravitational coupling and the speed of light are considered as space-time functions and define the scalar field. The cosmological coupling is analyzed to show the existence of an attractor point in the phase space. The condition for the coupling ratio between the gravitational coupling and the speed of light is derived for the cosmic evolution after reaching a stable fixed point. The impact of covarying gravitational coupling and speed of light on cosmic evolution is investigated by constructing a generalized continuity equation and solving modified Friedmann equations.
Article
Astronomy & Astrophysics
M. Yoshimura
Summary: We propose models that predict the presence of dark energy, cold dark matter, and slow-roll inflation simultaneously. The density of dark energy is found to be of order (a few meV )(4), and the mass of dark matter constituent is approximately 1 meV. These models incorporate a multiscalar tensor gravity with nontrivial conformal coupling to the Ricci scalar curvature in the Lagrangian density, and make use of the spatially homogeneous kinetic contribution of Nambu-Goldstone modes in a spontaneously broken multiscalar field sector to explain the amount of dark energy. The proposed theories are consistent with general relativity tests at small cosmological distances but differ from general relativity at cosmological scales.
Article
Astronomy & Astrophysics
Jan Ambjorn, Zbigniew Drogosz, Jakub Gizbert-Studnicki, Andrzej Gorlich, Jerzy Jurkiewicz, Daniel Nemeth
Summary: This article discusses the complex geometries extracted from the path integral of a quantum theory of gravity, showing that using suitable coordinate systems and scalar fields that solve Laplace's equation can help understand cosmic voids and filaments structures. It also demonstrates the dramatic changes in geometry that can occur when scalar fields are dynamically coupled to the geometry.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Multidisciplinary Sciences
Sergei V. Chervon, Igor V. Fomin
Summary: This study examines scalar-torsion gravity theories with exact solutions based on a physical type of potential for cosmological inflationary models involving the non-minimal coupling of a scalar field and torsion. Different inflationary dynamics and corresponding scalar field parameters are analyzed. This approach allows for the consideration of various physical potentials and types of scalar-torsion gravity theories in the realization of two stages of accelerated expansion in the universe. The correspondence between the proposed inflationary models and observational constraints on cosmological perturbation parameters is also explored.
Article
Mathematics
Alfredo D. Millano, Genly Leon, Andronikos Paliathanasis
Summary: We perform a detailed study of the phase-space of the field equations of an Einstein-Gauss-Bonnet scalar field cosmology for a spatially flat Friedmann-Lemaitre-Robertson-Walker spacetime. We consider the exponential function for the scalar field potential and assume two cases for the coupling function of the scalar field with the Gauss-Bonnet term: the exponential function and the power-law function. By writing the field equations in dimensionless variables and studying the equilibrium points using normalized and compactified variables, we recover previous results and discover new asymptotic solutions. These couplings provide a rich cosmological phenomenology.
Article
Physics, Multidisciplinary
Andronikos Paliathanasis
Summary: We address the group classification problem for gravitational field equations within the context of brane-world cosmology, considering the presence of a bulk scalar field. By applying the Lie symmetry condition, we find that only the exponential potential exhibits Lie symmetries, and we derive exact solutions for the system using Lie invariants.
Article
Astronomy & Astrophysics
Goutam Mandal, Soumya Chakraborty, Sudip Mishra, Sujay Kr. Biswas
Summary: In this work, a scalar field model is investigated as a candidate for dark energy, interacting with pressure-less dark matter, from a dynamical systems perspective. Two different interaction models are considered, and several critical points and solutions are derived. Stability analyses are performed for both two-dimensional and four-dimensional systems. The study reveals the evolution of the universe and the existence of transient solutions resembling de Sitter solutions.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Mathematics, Applied
Pedro-Maria Alcover-Garau
Summary: Discrete quadratic dynamical systems are used to define models of reality. The behavior of their complex orbits can be understood by studying the Mandelbrot Set. Symmetrical points on the map of periods, generated by encoding the orbits of points in the Mandelbrot Set, play a significant role in determining the values of other points. Understanding the properties of these points is crucial for comprehending the behavior of quadratic and discrete dynamical systems. The article highlights the emergence of scalar symmetry property and its impact on the hypersensitivity of the map of periods to small changes in parameters.
DISCRETE AND CONTINUOUS DYNAMICAL SYSTEMS-SERIES B
(2023)
Article
Physics, Particles & Fields
Shao-Jun Zhang
Summary: A study was conducted on massive scalar field perturbation on Kerr black holes in dynamical Chern-Simons gravity through a (2+1)-dimensional simulation. It was found that tachyonic instability always occurs when the coupling constant exceeds a critical value, for any nonzero black hole spin and any scalar field mass. The presence of a mass term suppresses or even quenches the instability, with the quantitative dependence of the onset of tachyonic instability on the coupling constant, scalar field mass, and black hole spin given numerically.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Physics, Particles & Fields
Aleksander Stachowski, Marek Szydlowski, Krzysztof Urbanowski
EUROPEAN PHYSICAL JOURNAL C
(2017)
Article
Physics, Particles & Fields
Marek Szydlowski, Aleksander Stachowski, Krzysztof Urbanowski
EUROPEAN PHYSICAL JOURNAL C
(2017)
Article
Physics, Particles & Fields
Marek Szydlowski, Aleksander Stachowski, Andrzej Borowiec
EUROPEAN PHYSICAL JOURNAL C
(2017)
Article
Physics, Particles & Fields
Aleksander Stachowski, Marek Szydlowski, Andrzej Borowiec
EUROPEAN PHYSICAL JOURNAL C
(2017)
Article
Astronomy & Astrophysics
Marek Szydlowski, Aleksander Stachowski
PHYSICS OF THE DARK UNIVERSE
(2017)
Article
Physics, Particles & Fields
Marek Szydlowski, Aleksander Stachowski
EUROPEAN PHYSICAL JOURNAL C
(2018)
Article
Physics, Particles & Fields
Marek Szydlowski, Aleksander Stachowski
EUROPEAN PHYSICAL JOURNAL C
(2018)
Article
Astronomy & Astrophysics
A. R. Kurek, A. Stachowski, K. Banaszek, A. Pollo
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2018)
Article
Physics, Particles & Fields
Aleksander Stachowski, Marek Szydlowski, Krzysztof Urbanowski
ADVANCES IN HIGH ENERGY PHYSICS
(2018)
Article
Astronomy & Astrophysics
Marek Szydlowski, Aleksander Stachowski, Krzysztof Urbanowski
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2020)
Article
Physics, Particles & Fields
Orest Hrycyna
EUROPEAN PHYSICAL JOURNAL C
(2020)
Article
Astronomy & Astrophysics
Orest Hrycyna
Summary: Dynamical systems methods were used to investigate a cosmological model with a non-minimally coupled scalar field and asymptotically quadratic potential function. The study found an unstable asymptotic de Sitter state for certain values of the non-minimal coupling constant parameter, leading to a non-singular beginning of the universe. The proposed evolutional model is generic, structurally stable, and independent of the specific choice of initial conditions in phase space.
Proceedings Paper
Mechanics
A. Stachowski, M. Szydlowski, K. Urbanowski
9TH INTERNATIONAL WORKSHOP DICE2018: SPACETIME - MATTER - QUANTUM MECHANICS
(2019)
Article
Astronomy & Astrophysics
Marek Szydlowski, Aleksander Stachowski
Proceedings Paper
Astronomy & Astrophysics
Orest Hrycyna
3RD CONFERENCE OF THE POLISH SOCIETY ON RELATIVITY, 2016
(2017)