scholarly journals Phantom dark energy from scalar-torsion coupling

2020 ◽  
pp. 2050331
Author(s):  
Nikodem J. Popławski
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Lagrangian Density ◽  
Kinetic Term ◽  
Equivalent Formulation ◽  
Phantom Dark Energy ◽  
General Relativistic ◽  
Theory Of Gravity ◽  
Cartan Theory

We show that a scalar field without a kinetic term in the Lagrangian density, coupled to the covariant divergence of the torsion vector in the Einstein–Cartan theory of gravity, becomes kinetic in its general-relativistic equivalent formulation. The resulting kinetic term is negative: such a scalar field could be a source of phantom dark energy.

Phantom dark energy models with negative kinetic term

2006 ◽  
Vol 74 (8) ◽  
Author(s):  
Jens Kujat ◽  
Robert J. Scherrer ◽  
A. A. Sen
Keyword(s):  
Dark Energy ◽  
Kinetic Term ◽  
Energy Models ◽  
Phantom Dark Energy

scholarly journals First Order Framework for Gauge k-Vortices

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
D. Bazeia ◽  
L. Losano ◽  
M. A. Marques ◽  
R. Menezes
Keyword(s):  
Scalar Field ◽  
Energy Density ◽  
Boundary Conditions ◽  
Unit Circle ◽  
Analytical Solutions ◽  
Covariant Derivative ◽  
Lagrangian Density ◽  
Kinetic Term ◽  
First Order

We study vortices in generalized Maxwell-Higgs models, with the inclusion of a quadratic kinetic term with the covariant derivative of the scalar field in the Lagrangian density. We discuss the stressless condition and show that the presence of analytical solutions helps us to define the model compatible with the existence of first order equations. A method to decouple the first order equations and to construct the model is then introduced and, as a bonus, we get the energy depending exclusively on a function of the fields calculated from the boundary conditions. We investigate some specific possibilities and find, in particular, a compact vortex configuration in which the energy density is all concentrated in a unit circle.

scholarly journals DARK ENERGY, DARK MATTER AND GRAVITY

2007 ◽  
Vol 16 (12a) ◽  
pp. 2003-2012 ◽  
Author(s):  
ORFEU BERTOLAMI
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Solar System ◽  
Physical Theory ◽  
Scalar Fields ◽  
High Accuracy ◽  
Scalar Theory ◽  
General Relativistic ◽  
Cosmological Tests ◽  
Theory Of Gravity

We discuss the motivation for high accuracy relativistic gravitational experiments in the solar system and complementary cosmological tests. We focus our attention on the issue of distinguishing a generic scalar theory of gravity as the underlying physical theory from the usual general-relativistic picture, where one expects the presence of fundamental scalar fields associated, for instance, with inflation, dark matter and dark energy.

scholarly journals Unified Dark Matter Scalar Field Models

2010 ◽  
Vol 2010 ◽  
pp. 1-29 ◽  
Author(s):  
Daniele Bertacca ◽  
Nicola Bartolo ◽  
Sabino Matarrese
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Galactic Halo ◽  
Kinetic Term ◽  
Spherically Symmetric ◽  
Rotation Curves ◽  
Spherically Symmetric Solutions ◽  
Scalar Field Models ◽  
Unified Description

We analyze and review cosmological models in which the dynamics of a single scalar field accounts for a unified description of the Dark Matter and Dark Energy sectors, dubbed Unified Dark Matter (UDM) models. In this framework, we consider the general Lagrangian of -essence, which allows to find solutions around which the scalar field describes the desired mixture of Dark Matter and Dark Energy. We also discuss static and spherically symmetric solutions of Einstein's equations for a scalar field with noncanonical kinetic term, in connection with galactic halo rotation curves.

scholarly journals UNIFIED DARK MATTER IN SCALAR FIELD COSMOLOGIES

2007 ◽  
Vol 22 (38) ◽  
pp. 2893-2907 ◽  
Author(s):  
DANIELE BERTACCA ◽  
SABINO MATARRESE ◽  
MASSIMO PIETRONI
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Cosmological Constant ◽  
Sound Speed ◽  
State Parameter ◽  
Equation Of Motion ◽  
Kinetic Term ◽  
Fluid Equation ◽  
Classical Trajectories

Considering the general Lagrangian of k-essence models, we study and classify them through variables connected to the fluid equation of state parameter wκ. This allows one to find solutions around which the scalar field describes a mixture of dark matter and cosmological constant-like dark energy, an example being the purely kinetic model proposed by Scherrer. Making the stronger assumption that the scalar field Lagrangian is exactly constant along solutions of the equation of motion, we find a general class of k-essence models whose classical trajectories directly describe a unified dark matter/dark energy (cosmological constant) fluid. While the simplest case of a scalar field with canonical kinetic term unavoidably leads to an effective sound speed cs = 1, thereby inhibiting the growth of matter inhomogeneities, more general non-canonical k-essence models allow for the possibility that cs≪1 whenever matter dominates.

scholarly journals SCALAR, FOUR VOLUME AND HOLOGRAPHIC DARK ENERGY

2012 ◽  
Vol 10 ◽  
pp. 95-106 ◽  
Author(s):  
CHANGJUN GAO
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Holographic Dark Energy ◽  
Specific Form ◽  
Holographic Dark Energy Model ◽  
Cosmic Evolution ◽  
Dimensional Spacetime ◽  
Phantom Dark Energy ◽  
Acceleration Of The Universe ◽  
The Universe

We explore the cosmic evolution of a scalar field which is identified with the four dimensional spacetime volume. Given a specific form for the Lagrangian of the scalar field, a new holographic dark energy model is present. The energy density of dark energy is reversely proportional to the square of the radius of the cosmic null hypersurface which is present as a new infrared cutoff for the Universe. We find this holographic dark energy belongs to the phantom dark energy for some appropriate parameters in order to interpret the current acceleration of the Universe.

scholarly journals GENERAL COORDINATE TRANSFORMATIONS AS THE ORIGINS OF DARK ENERGY

2007 ◽  
Vol 22 (04) ◽  
pp. 749-776 ◽  
Author(s):  
VINCENT G. J. RODGERS ◽  
TAKESHI YASUDA
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Virasoro Algebra ◽  
Field Theories ◽  
One Dimension ◽  
Coordinate Transformations ◽  
Moody Algebra ◽  
Gauge Transformations ◽  
Yang Mills ◽  
Phantom Dark Energy

In this note we demonstrate that the algebra associated with coordinate transformations might contain the origins of a scalar field that can behave as an inflaton and/or a source for dark energy. We will call this particular scalar field the diffeomorphism scalar field. In one dimension, the algebra of coordinate transformations is the Virasoro algebra while the algebra of gauge transformations is the Kac–Moody algebra. An interesting representation of these algebras corresponds to certain field theories that have meaning in any dimension. In particular, the so-called Kac–Moody sector corresponds to Yang–Mills theories and the Virasoro sector corresponds to the diffeomorphism field theory that contains the scalar field and a rank-two symmetric, traceless tensor. We will focus on the contributions of the diffeomorphism scalar field to cosmology. We show that this scalar field can, qualitatively, act as a phantom dark energy, an inflaton, a dark matter source, and the cosmological constant Λ.

scholarly journals Anisotropic dark energy Bianchi type III cosmological models in the Brans–Dicke theory of gravity

2012 ◽  
Vol 90 (2) ◽  
pp. 193-198 ◽  
Author(s):  
Muhammad Farasat Shamir ◽  
Akhlaq Ahmad Bhatti
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Cosmological Model ◽  
Bianchi Type ◽  
Constant Deceleration Parameter ◽  
Physical Behavior ◽  
Type Iii ◽  
Anisotropic Dark Energy ◽  
Theory Of Gravity ◽  
Physical Quantities

The main purpose of this paper is to explore the solutions of Bianchi type III cosmological model in Brans–Dicke theory of gravity in the background of anisotropic dark energy. We use the assumption of constant deceleration parameter and power law relation between scalar field [Formula: see text] and scale factor a to find the solutions. The physical behavior of the solutions has been discussed using some physical quantities.

Effective masses in a dense fermion background — Applied to neutrinos, dark matter and dark energy

2014 ◽  
Vol 29 (21) ◽  
pp. 1444010
Author(s):  
Bruce H. J. McKellar ◽  
T. J. Goldman ◽  
G. J. Stephenson
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Effective Mass ◽  
Negative Pressure ◽  
Expectation Value ◽  
Effective Masses ◽  
Neutrino Astrophysics

If fermions interact with a scalar field, and there are many fermions present the scalar field may develop an expectation value and generate an effective mass for the fermions. This can lead to the formation of fermion clusters, which could be relevant for neutrino astrophysics and for dark matter astrophysics. Because this system may exhibit negative pressure, it also leads to a model of dark energy.

Sign in / Sign up

Export Citation Format

Share Document