WIGGLY COSMIC STRINGS ACCRETE DARK ENERGY

2006 ◽  
Vol 15 (04) ◽  
pp. 603-613 ◽  
Author(s):  
PEDRO F. GONZÁLEZ-DÍAZ ◽  
JOSÉ A. JIMÉNEZ MADRID
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Cosmic Strings ◽  
Energy Condition ◽  
Phantom Energy ◽  
Dominant Energy Condition ◽  
Final State ◽  
Cylindrically Symmetric ◽  
Energy Models ◽  
Maximum Value

This paper deals with a study of the cylindrically symmetric accretion of dark energy with equation of state p = wρ onto wiggly straight cosmic strings, interpreting that the accreted energy only contributes the extent of the wiggliness, but consistently leaves invariant the unperturbed line density μ0. We have obtained that when w > -1, the perturbed linear energy density in the string core gradually increases tending to a finite maximum value as time increases, for all considered dark energy models. Where the dominant energy condition is violated, all such models predict a steady decreasing of the perturbed linear energy density μ of the cosmic strings as phantom energy is being accreted. The final state of the string after such an accretion process is a wiggleless defect. It is argued however, that if accreation of phantom energy would proceed by successive quantum steps, then the defect would continue losing perturbed linear energy density beyond μ0, until a minimum nonzero value which can be smaller than that corresponding to the unperturbed string.

scholarly journals Violation of the Dominant Energy Condition in Geometrodynamics

Symmetry ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 400
Author(s):  
Vladimir Lasukov
Keyword(s):  
Black Holes ◽  
Dark Energy ◽  
Energy Condition ◽  
Dominant Energy Condition ◽  
Isotropic Energy ◽  
Cosmological Singularity ◽  
Dominant Condition ◽  
Field Theoretical Model ◽  
Over Time

It is shown that in Einstein’s theory and in the theory of gravity with Logunov constraints, there is a field-theoretical model of dark energy that is consistent with the observational data indicating that the Hubble value increases over time. In the developed model of dark energy, the isotropic energy dominant condition is violated. It solves the problem of the cosmological singularity and the singularity of “black holes”. The compact configuration of the scalar field can generate a flux of particles by the pairs of particles production mechanism from the vacuum by a field of barrier and in the process of transformation of thermal energy (Hawking radiation) and acceleration energy into radiation. The scalars can play the role of the so-called “black holes” with no singularity inside themselves.

scholarly journals SUPERNOVA Ia AND GALAXY CLUSTER GAS MASS FRACTION CONSTRAINTS ON DARK ENERGY

2006 ◽  
Vol 21 (29) ◽  
pp. 2197-2204 ◽  
Author(s):  
KYLE M. WILSON ◽  
GANG CHEN ◽  
BHARAT RATRA
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Cosmological Constant ◽  
Mass Fraction ◽  
Galaxy Cluster ◽  
Apparent Magnitude ◽  
Model Parameters ◽  
Dark Energy Density ◽  
Energy Models ◽  
Fraction Versus

We use the Riess et al. (2004)1 supernova Ia apparent magnitude versus redshift data and the Allen et al. (2004)2 galaxy cluster gas mass fraction versus redshift data to constrain dark energy models. These data provide complementary constraints that when combined together significantly restrict model parameters and favor slowly-evolving dark energy density models, close to the Einstein cosmological constant limit of dark energy.

scholarly journals Dark Matter Candidates with Dark Energy Interiors Determined by Energy Conditions

Symmetry ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 662 ◽  
Author(s):  
Irina Dymnikova
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Energy Condition ◽  
Phantom Energy ◽  
Weak Energy Condition ◽  
Energy Conditions ◽  
De Sitter ◽  
Dynamical Equations ◽  
De Sitter Vacuum ◽  
Observational Signature

We outline the basic properties of regular black holes, their remnants and self-gravitating solitons G-lumps with the de Sitter and phantom interiors, which can be considered as heavy dark matter (DM) candidates generically related to a dark energy (DE). They are specified by the condition T t t = T r r and described by regular solutions of the Kerr-Shild class. Solutions for spinning objects can be obtained from spherical solutions by the Newman-Janis algorithm. Basic feature of all spinning objects is the existence of the equatorial de Sitter vacuum disk in their deep interiors. Energy conditions distinguish two types of their interiors, preserving or violating the weak energy condition dependently on violation or satisfaction of the energy dominance condition for original spherical solutions. For the 2-nd type the weak energy condition is violated and the interior contains the phantom energy confined by an additional de Sitter vacuum surface. For spinning solitons G-lumps a phantom energy is not screened by horizons and influences their observational signatures, providing a source of information about the scale and properties of a phantom energy. Regular BH remnants and G-lumps can form graviatoms binding electrically charged particles. Their observational signature is the electromagnetic radiation with the frequencies depending on the energy scale of the interior de Sitter vacuum within the range available for observations. A nontrivial observational signature of all DM candidates with de Sitter interiors predicted by analysis of dynamical equations is the induced proton decay in an underground detector like IceCUBE, due to non-conservation of baryon and lepton numbers in their GUT scale false vacuum interiors.

Diagnosing Tsallis holographic dark energy models with statefinder and ω − ω′ pair

2019 ◽  
Vol 34 (13) ◽  
pp. 1950101 ◽  
Author(s):  
Umesh Kumar Sharma ◽  
Anirudh Pradhan
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Holographic Dark Energy ◽  
Tsallis Entropy ◽  
Observation Data ◽  
Energy Models ◽  
Evolutionary Trajectories

A useful method, known as statefinder diagnostic, which may differentiate one dark energy (DE) model from others is applied in this work to a holographic dark energy (HDE) model from Tsallis entropy, called the Tsallis holographic dark energy (THDE) model. The evolutionary trajectories of this model are plotted in the statefinder parameter — planes and [Formula: see text] plane, and it is observed that the parameter [Formula: see text] of this model plays a magnificent role from the statefinder and [Formula: see text] plane viewpoints. Eventually, the evolutionary trajectories are plotted considering two different values of THDE energy density ([Formula: see text]), [Formula: see text], in the light of Planck 2018 results VI base-LCDM cosmology and [Formula: see text], in the light of SNe + BAO + OHD + CMB observation data.

scholarly journals Unphysical properties in a class of interacting dark energy models

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
R. von Marttens ◽  
H. A. Borges ◽  
S. Carneiro ◽  
J. S. Alcaniz ◽  
W. Zimdahl
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Energy Condition ◽  
Matter Density ◽  
Dark Energy Density ◽  
Energy Models ◽  
Cosmological Scenario ◽  
Selection For ◽  
Interacting Dark Energy Models ◽  
Energy Components

AbstractModels with non-gravitational interactions between the dark matter and dark energy components are an alternative to the standard cosmological scenario. These models are characterized by an interaction term, and a frequently used parameterization is $$Q = 3\xi H \rho _{x}$$ Q = 3 ξ H ρ x , where H is the Hubble parameter and $$\rho _{x}$$ ρ x is the dark energy density. Although recent analyses have reported that this particular scenario provides a potential solution to the $$H_{0}$$ H 0 and $$\sigma _{8}$$ σ 8 tensions for negative values of the interaction parameter $$\xi $$ ξ , we show here that such an interval of values of $$\xi $$ ξ leads to a violation of the Weak Energy Condition for the dark matter density, which is accompanied by unphysical instabilities of matter perturbations. Using current observational data we also show that the inclusion of the physical prior $$\xi \ge 0$$ ξ ≥ 0 in the statistical analysis alters the parameter selection for this model and discards it as a solution for the $$H_{0}$$ H 0 -tension problem.

scholarly journals Some models of holographic dark energy on the Randall–Sundrum brane and observational data

2019 ◽  
Vol 29 (01) ◽  
pp. 1950176 ◽  
Author(s):  
A. V. Astashenok ◽  
A. S. Tepliakov
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Observational Data ◽  
Energy Analysis ◽  
Holographic Dark Energy ◽  
Brane Tension ◽  
Dark Energy Density ◽  
Energy Models ◽  
Current Energy ◽  
The Universe

Some models of holographic dark energy for Randall–Sundrum brane are considered. For the first class of dark energy models, we take energy density in the form [Formula: see text], where [Formula: see text] is size of event horizon in universe and [Formula: see text] is parameter (Tsallis holographic energy). Analysis of observational data allows to define upper limit on value of [Formula: see text] ([Formula: see text] is current energy density in the universe and [Formula: see text] is brane tension). Then we investigate models for which dark energy density has the form [Formula: see text] where [Formula: see text] is Hubble parameter.

scholarly journals NULL ENERGY CONDITION AND DARK ENERGY MODELS

2008 ◽  
Vol 23 (32) ◽  
pp. 2787-2798 ◽  
Author(s):  
TAOTAO QIU ◽  
YI-FU CAI ◽  
XINMIN ZHANG
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Field Model ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Scalar Model ◽  
Phantom Model ◽  
Energy Models ◽  
Short Period ◽  
The Universe

Null Energy Condition (NEC) requires the equation of state (EoS) of the universe wu satisfy wu ≥ -1, which implies, for instance in a universe with matter and dark energy dominating wu = w m Ω m + w de Ω de = w de Ω de ≥ -1. In this paper we study constraints on the dark energy models from the requirement of the NEC. We will show that with Ω de ~ 0.7, w de < -1 at present epoch is possible. However, NEC excludes the possibility of w de < -1 forever as happened in the Phantom model, but if w de < -1 stays for a short period of time as predicted in the Quintom theory, NEC can be satisfied. We take three examples of Quintom models of dark energy, namely the phenomenological EoS, the two-scalar-field model and the single scalar model with a modified Dirac–Born–Infeld (DBI) Lagrangian to show how this happens.

scholarly journals A Study on Some Special Forms of Holographic Ricci Dark Energy in Fractal Universe

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Surajit Chattopadhyay ◽  
Antonio Pasqua ◽  
Sudipto Roy
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Deceleration Parameter ◽  
Hubble Parameter ◽  
Equations Of State ◽  
State Parameter ◽  
Ricci Dark Energy ◽  
Energy Models

We have considered the modified and the extended holographic Ricci dark energy models (MHRDE and EHRDE) in fractal universe. We have assumed a time-like fractal profile v=t−β, where β=4(1−α). We have reconstructed the Hubble parameter H, the energy density, the equations of state parameter w, and the deceleration parameter q for both MHRDE and EHRDE.

scholarly journals Taxonomy of Dark Energy Models

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 163
Author(s):  
Verónica Motta ◽  
Miguel A. García-Aspeitia ◽  
Alberto Hernández-Almada ◽  
Juan Magaña ◽  
Tomás Verdugo
Keyword(s):  
Dark Energy ◽  
Cold Dark Matter ◽  
Accelerated Expansion ◽  
Energy Component ◽  
The Past ◽  
Energy Models ◽  
The Status ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Unknown Component

The accelerated expansion of the Universe is one of the main discoveries of the past decades, indicating the presence of an unknown component: the dark energy. Evidence of its presence is being gathered by a succession of observational experiments with increasing precision in its measurements. However, the most accepted model for explaining the dynamic of our Universe, the so-called Lambda cold dark matter, faces several problems related to the nature of such energy component. This has led to a growing exploration of alternative models attempting to solve those drawbacks. In this review, we briefly summarize the characteristics of a (non-exhaustive) list of dark energy models as well as some of the most used cosmological samples. Next, we discuss how to constrain each model’s parameters using observational data. Finally, we summarize the status of dark energy modeling.

Sign in / Sign up

Export Citation Format

Share Document