scholarly journals Gravitational decoupling and superfluid stars

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
Roldao da Rocha
Keyword(s):  
Scalar Field ◽  
Observational Data ◽  
Mass Function ◽  
The Self ◽  
Brane Tension ◽  
Relativistic Limit ◽  
Asymptotic Value ◽  
General Relativistic ◽  
Physical Features ◽  
Scalar Gravity

AbstractThe gravitational decoupling is applied to studying minimal geometric deformed (MGD) compact superfluid stars, in covariant logarithmic scalar gravity on fluid branes. The brane finite tension is shown to provide more realistic values for the asymptotic value of the mass function of MGD superfluid stars, besides constraining the range of the self-interacting scalar field, minimally coupled to gravity. Several other physical features of MGD superfluid stars, regulated by the finite brane tension and a decoupling parameter, are derived and discussed, with important corrections to the general-relativistic limit that corroborate to current observational data.

scholarly journals RASTALL COSMOLOGY

2012 ◽  
Vol 18 ◽  
pp. 67-76 ◽  
Author(s):  
JÚLIO C. FABRIS ◽  
OLIVER F. PIATTELLA ◽  
DAVI C. RODRIGUES ◽  
CARLOS E. M. BATISTA ◽  
MAHAMADOU H. DAOUDA
Keyword(s):  
Scalar Field ◽  
Observational Data ◽  
Canonical Form ◽  
Conservation Law ◽  
Chaplygin Gas ◽  
Cosmological Models ◽  
The Self ◽  
Generalized Chaplygin Gas ◽  
Field Representation ◽  
Theory Of Gravity

We review the difficulties of the generalized Chaplygin gas model to fit observational data, due to the tension between background and perturbative tests. We argue that such issues may be circumvented by means of a self-interacting scalar field representation of the model. However, this proposal seems to be successful only if the self-interacting scalar field has a non-canonical form. The latter can be implemented in Rastall's theory of gravity, which is based on a modification of the usual matter conservation law. We show that, besides its application to the generalized Chaplygin gas model, other cosmological models based on Rastall's theory have many interesting and unexpected new features.

scholarly journals Gravitational decoupling of generalized Horndeski hybrid stars

2022 ◽  
Vol 82 (1) ◽  
Author(s):  
Roldao da Rocha
Keyword(s):  
General Relativity ◽  
Physical Properties ◽  
Neutron Stars ◽  
Observational Data ◽  
White Dwarfs ◽  
Mass Function ◽  
Effective Radius ◽  
Asymptotic Value ◽  
Klein Gordon ◽  
Hybrid Stars

AbstractGravitational decoupled compact polytropic hybrid stars are here addressed in generalized Horndeski scalar-tensor gravity. Additional physical properties of hybrid stars are scrutinized and discussed in the gravitational decoupling setup. The asymptotic value of the mass function, the compactness, and the effective radius of gravitational decoupled hybrid stars are studied for both cases of a bosonic and a fermionic prevalent core. These quantities are presented and discussed as functions of Horndeski parameters, the decoupling parameter, the adiabatic index, and the polytropic constant. Important corrections to general relativity and generalized Horndeski scalar-tensor gravity, induced by the gravitational decoupling, comply with available observational data. Particular cases involving white dwarfs, boson stellar configurations, neutron stars, and Einstein–Klein–Gordon solutions, formulated in the gravitational decoupling context, are also scrutinized.

A class of inflaton potentials from RG analysis of scalar-gravity interaction

2014 ◽  
Vol 11 (02) ◽  
pp. 1460008
Author(s):  
Artur R. Pietrykowski
Keyword(s):  
Renormalization Group ◽  
Scalar Field ◽  
Observational Data ◽  
Particle Physics ◽  
Field System ◽  
Group Methods ◽  
Renormalization Group Methods ◽  
Scalar Gravity ◽  
Inflationary Models ◽  
The Way

Inflationary models are characterized by the form of a potential which is arbitrary and usually parametrized so as to match the observational data. However, making use of the renormalization group methods to a gravity-scalar field system it is possible to find physically nontrivial potentials that might be relevant for cosmology and particle physics as well. I will pinpoint the way this class of potentials may be found as well as discuss their utility for inflationary models.

scholarly journals Tachyonic matter cosmology with exponential and hyperbolic potentials

2017 ◽  
Vol 26 (02) ◽  
pp. 1750012 ◽  
Author(s):  
B. Pourhassan ◽  
J. Naji
Keyword(s):  
Scalar Field ◽  
Observational Data ◽  
Cosmological Parameters ◽  
Field Potentials ◽  
Exponential Potential ◽  
Frw Universe ◽  
Hyperbolic Cosine ◽  
Special Cases ◽  
Friedmann Robertson Walker ◽  
Type Potential

In this paper, we consider tachyonic matter in spatially flat Friedmann–Robertson–Walker (FRW) universe, and obtain behavior of some important cosmological parameters for two special cases of potentials. First, we assume the exponential potential and then consider hyperbolic cosine type potential. In both cases, we obtain behavior of the Hubble, deceleration and EoS parameters. Comparison with observational data suggest the model with hyperbolic cosine type scalar field potentials has good model to describe universe.

Classical electrodynamics: the equation of motion

1974 ◽  
Vol 76 (1) ◽  
pp. 359-367 ◽  
Author(s):  
P. A. Hogan
Keyword(s):  
Electromagnetic Field ◽  
Charged Particle ◽  
Scalar Field ◽  
World Line ◽  
External Electromagnetic Field ◽  
Equation Of Motion ◽  
The Self ◽  
Classical Electrodynamics ◽  
Field Equations ◽  
The World

In this paper we derive the Lorentz-Dirac equation of motion for a charged particle moving in an external electromagnetic field. We use Maxwell's electromagnetic field equations together with the assumptions (1) that all fields are retarded and (2) that the 4-force acting on the charged particle is a Lorentz 4-force. To define the self-field on the world-line of the charge we utilize a contour integral representation for the field due to A. W. Conway. This by-passes the need to define an ‘average field’. In an appendix the case of a scalar field is briefly discussed.

CONFORMAL COUPLING'S OUTRAGEOUS LEGACY

2002 ◽  
Vol 11 (10) ◽  
pp. 1531-1536
Author(s):  
L. RAUL ABRAMO ◽  
LEON BRENIG ◽  
EDGARD GUNZIG
Keyword(s):  
Scalar Field ◽  
Scalar Curvature ◽  
The Other ◽  
Minimal Coupling ◽  
Quantum Stability ◽  
Paradoxical Situation ◽  
Other Hand ◽  
The One ◽  
Hilbert Action ◽  
Scalar Gravity

In Einstein's gravity, non-minimal coupling of a scalar field to the scalar curvature leads to a paradoxical situation. On the one hand, it opens the way to qualitatively new cosmological dynamics. On the other hand, there are sectors of non-minimally coupled scalar-gravity theories for which the Einstein–Hilbert action reverses its sign, which seems to indicate that the whole system is unstable. We show how conformal coupling bypasses this problem. Due to a subtle interplay between gravity and the scalar field, classical and quantum stability are guaranteed globally. This liberates conformal coupling from a serious obstacle. Inflationary solutions in the new sector are also presented, which are validated by current observations.

scholarly journals Lowering the self-coupling of the scalar field in the generalized Higgs inflation

2018 ◽  
Vol 363 (7) ◽  
Author(s):  
Kourosh Nozari ◽  
Somayeh Shafizadeh ◽  
Narges Rashidi
Keyword(s):  
Scalar Field ◽  
The Self

Complexity factors for static axial system in self-interacting Brans–Dicke gravity

2019 ◽  
Vol 16 (11) ◽  
pp. 1950174 ◽  
Author(s):  
M. Sharif ◽  
Amal Majid
Keyword(s):  
Scalar Field ◽  
Evolution Equations ◽  
Riemann Tensor ◽  
Additional Source ◽  
Bianchi Identities ◽  
Structure Scalars ◽  
Physical Attributes ◽  
Physical Features ◽  
Axial System

This paper explores the physical attributes of a static axial source that induce complexity within the fluid in the background of self-interacting Brans–Dicke theory. Bel’s approach is used to split the Riemann tensor and construct structure scalars that involve physical features of the fluid in the presence of scalar field. Using the evolution equations derived from Bianchi identities as well as structure scalars, five complexity factors are identified which include constraints on the scalar field. Finally, the conditions of vanishing complexity are used to present solutions for an anisotropic inhomogeneous spheroid. It is concluded that scalar field is an additional source of complexity.

A study of dynamical equations for non-minimally coupled scalar field using Noether symmetric approach

2016 ◽  
Vol 31 (19) ◽  
pp. 1650116 ◽  
Author(s):  
Sourav Dutta ◽  
Madan Mohan Panja ◽  
Subenoy Chakraborty
Keyword(s):  
Scalar Field ◽  
Infinitesimal Generator ◽  
Einstein Gravity ◽  
Matter Content ◽  
The Self ◽  
Noether Symmetry ◽  
Dynamical Equations ◽  
Augmented Space ◽  
Constants Of Motion ◽  
Scalar Field Cosmology

Non-minimally coupled scalar field cosmology has been studied in this work within the framework of Einstein gravity. In the background of homogeneous and isotropic Friedmann–Lemaitre–Robertson–Walker (FLRW) spacetime non-minimally coupled scalar field having self-interacting potential is taken as the source of the matter content. The constraint of imposing Noether symmetry on the Lagrangian of the system not only determines the infinitesimal generator (the symmetry vector) but also the coupling function and the self-interacting potential for the scalar field. By choosing appropriately a point transformation in the augmented space, one of the transformed variables is cyclic for the Lagrangian. Finally, using constants of motion, the solutions are analyzed.

Sign in / Sign up

Export Citation Format

Share Document