scholarly journals Field Equations and Radial Solutions in a Noncommutative Spherically Symmetric Geometry

2014 ◽  
Vol 2014 ◽  
pp. 1-9
Author(s):  
Aref Yazdani
Keyword(s):  
Line Element ◽  
Teleparallel Gravity ◽  
State Theory ◽  
Radial Solutions ◽  
Field Equations ◽  
Force Equation ◽  
Symmetric Geometry ◽  
Noncommutative Gauge Theory ◽  
Theories Of Gravity ◽  
First Time

We study a noncommutative theory of gravity in the framework of torsional spacetime. This theory is based on a Lagrangian obtained by applying the technique of dimensional reduction of noncommutative gauge theory and that the yielded diffeomorphism invariant field theory can be made equivalent to a teleparallel formulation of gravity. Field equations are derived in the framework of teleparallel gravity through Weitzenbock geometry. We solve these field equations by considering a mass that is distributed spherically symmetrically in a stationary static spacetime in order to obtain a noncommutative line element. This new line element interestingly reaffirms the coherent state theory for a noncommutative Schwarzschild black hole. For the first time, we derive the Newtonian gravitational force equation in the commutative relativity framework, and this result could provide the possibility to investigate examples in various topics in quantum and ordinary theories of gravity.

Phase space correspondence between Jordan and Einstein frames

2021 ◽  
pp. 2150087
Author(s):  
Amin Salehi
Keyword(s):  
Phase Space ◽  
Critical Point ◽  
Critical Points ◽  
Dynamical Behavior ◽  
Cosmological Parameters ◽  
Jordan Frame ◽  
Field Equations ◽  
Theories Of Gravity ◽  
The Stability ◽  
Jordan And Einstein Frames

Scalar–tensor theories of gravity can be formulated in the Einstein frame or in the Jordan frame (JF) which are related with each other by conformal transformations. Although the two frames describe the same physics and are equivalent, the stability of the field equations in the two frames is not the same. Here, we implement dynamical system and phase space approach as a robustness tool to investigate this issue. We concentrate on the Brans–Dicke theory in a Friedmann–Lemaitre–Robertson–Walker universe, but the results can easily be generalized. Our analysis shows that while there is a one-to-one correspondence between critical points in two frames and each critical point in one frame is mapped to its corresponds in another frame, however, stability of a critical point in one frame does not guarantee the stability in another frame. Hence, an unstable point in one frame may be mapped to a stable point in another frame. All trajectories between two critical points in phase space in one frame are different from their corresponding in other ones. This indicates that the dynamical behavior of variables and cosmological parameters is different in two frames. Hence, for those features of the study, which focus on observational measurements, we must use the JF where experimental data have their usual interpretation.

Kinetic study on the linalool ozonolysis reaction in the atmosphere

2012 ◽  
Vol 90 (4) ◽  
pp. 353-361 ◽  
Author(s):  
Xiaomin Sun ◽  
Chenxi Zhang ◽  
Yuyang Zhao ◽  
Jing Bai ◽  
Maoxia He
Keyword(s):  
Rate Constants ◽  
Transition State Theory ◽  
State Theory ◽  
Oxidation Products ◽  
Tunneling Effect ◽  
Total Rate ◽  
Variational Transition State Theory ◽  
Atmospheric Lifetime ◽  
Ozone Addition ◽  
First Time

In the atmosphere, linalool ozonolysis will generate a series of oxidation products and then form particles through nucleation. In this study, the linalool ozonolysis mechanisms were studied and some of the main products detected from experiment are verified. The Rice–Ramsperger–Kassel–Marcus (RRKM) theory and the canonical variational transition state theory (CVT) with small curvature tunneling effect (SCT) are used to calculate rate constants over the temperature range of 200∼800 K. The total rate constant for the reaction of ozone with linalool is 4.50 × 10−16 cm3 molecule–l s–l, and the addition of ozone to (CH3)2C=CH– is the main ozone addition position. Furthermore, the Arrhenius formulas are fitted and the lifetimes of reaction species in the troposphere are discussed for the first time. The total atmospheric lifetime of linalool relative to O3 is 2.30 h. The O3-initiated atmospheric lifetimes of P1, P3, and P6 are 2.64 months, 16.67 days, and 15.5 h, respectively.

scholarly journals Accelerating Universe with Viscous Cosmic String in Quadratic Form of Teleparallel Gravity

2019 ◽  
Vol 11 (3) ◽  
pp. 249-262
Author(s):  
S. R. Bhoyar ◽  
V. R. Chirde ◽  
S. H. Shekh
Keyword(s):  
Cosmic String ◽  
Teleparallel Gravity ◽  
Negative Slope ◽  
Accelerating Universe ◽  
Field Equations ◽  
Physical Behavior ◽  
Torsion Scalar ◽  
Bulk Viscous ◽  
The Universe ◽  
Physical Quantities

In this paper, we have investigated Kantowaski-Sachs cosmological model with bulk viscous and cosmic string in the framework of Teleparallel Gravity so called f(T) gravity, where T denotes the torsion scalar. The behavior of accelerating universe is discussed towards the particular choice of f(T) = Α(T) + β(T)m. The exact solutions of the field equations are obtained by applying variable deceleration parameter which is linear in time with a negative slope. The physical behavior of these models has been discussed using some physical quantities. Also, the function of the torsion scalar for the universe is evaluated.

Exact wormholes solutions without exotic matter in f(R,T) gravity

2019 ◽  
Vol 16 (03) ◽  
pp. 1950046 ◽  
Author(s):  
M. Zubair ◽  
Rabia Saleem ◽  
Yasir Ahmad ◽  
G. Abbas
Keyword(s):  
Momentum Tensor ◽  
Exotic Matter ◽  
Gravity Models ◽  
Energy Conditions ◽  
Anisotropic Fluid ◽  
Energy Tensor ◽  
Field Equations ◽  
Stress Energy ◽  
Symmetric Geometry ◽  
The Stability

This paper is aimed to evaluate the existence of wormholes in viable [Formula: see text] gravity models (where [Formula: see text] is the scalar curvature and [Formula: see text] is the trace of stress–energy tensor of matter). The exact solutions for energy–momentum tensor components depending on different shapes and redshift functions are calculated without some additional constraints. To investigate this, we consider static spherically symmetric geometry with matter contents as anisotropic fluid and formulate the Einstein field equations for three different [Formula: see text] models. For each model, we derive expression for weak and null energy conditions and graphically analyzed its violation near the throat. It is really interesting that wormhole solutions do not require the presence of exotic matter — like that in general relativity. Finally, the stability of the solutions for each model is presented using equilibrium condition.

HOW MATTER IS CREATED IN VSL THEORY?

2004 ◽  
Vol 13 (07) ◽  
pp. 1437-1440 ◽  
Author(s):  
RICARDO B. NASCIMENTO ◽  
CALISTRATO S. CÂMARA ◽  
JOEL C. CARVALHO
Keyword(s):  
Line Element ◽  
Particle Creation ◽  
Second Law Of Thermodynamics ◽  
Einstein Equations ◽  
Second Law ◽  
Speed Of Light ◽  
Field Equations ◽  
Creation Rate ◽  
Friedmann Robertson Walker ◽  
Energy Conservation Law

In this work we investigate matter creation in the context of two types of varying speed of light (VSL) cosmologies. We write the energy conservation law arising from Einstein equations for a Friedmann–Robertson–Walker (FRW) line element in a flat universe, solve the field equations and study how particles are created as c changes with cosmic epoch. We calculate the "adiabatic" particle creation rate, the total number of particle as a function of time and find the constrains imposed by the second law of thermodynamics upon the models.

The general axially symmetric static solution of Einstein’s vacuum field equations

1982 ◽  
Vol 382 (1783) ◽  
pp. 467-470 ◽  
Keyword(s):  
General Solution ◽  
Potential Function ◽  
Line Element ◽  
Static Solution ◽  
Vacuum Field ◽  
Axially Symmetric ◽  
Field Equations ◽  
Axis Of Symmetry ◽  
Axisymmetric Solutions ◽  
Associated Function

The general solution in closed form, including all the static axisymmetric solutions of Weyl, is presented in the canonical coordinates ρ and z of his line element. This general solution is constructed from an arbitrary function f ( z ), which coincides with his potential function along the axis of symmetry. To illustrate how the solution may be used, a particular function f , one resulting from a Newtonian solution, is used to find both the potential function and its associated function in the line element.

scholarly journals General relativity and cosmology

2015 ◽  
Vol 24 (14) ◽  
pp. 1530030
Author(s):  
Martin Bucher ◽  
Wei-Tou Ni
Keyword(s):  
General Relativity ◽  
Quantum Gravity ◽  
Gravitational Waves ◽  
100Th Anniversary ◽  
Complete Theory ◽  
Historical Overview ◽  
Field Equations ◽  
First Time

This year marks the 100th anniversary of Einstein’s 1915 landmark paper “Die Feldgleichungen der Gravitation” in which the field equations of general relativity were correctly formulated for the first time, thus rendering general relativity a complete theory. Over the subsequent hundred years, physicists and astronomers have struggled with uncovering the consequences and applications of these equations. This paper, which was written as an introduction to six chapters dealing with the connection between general relativity and cosmology that will appear in the two-volume book One Hundred Years of General Relativity: From Genesis and Empirical Foundations to Gravitational Waves, Cosmology and Quantum Gravity, endeavors to provide a historical overview of the connection between general relativity and cosmology, two areas whose development has been closely intertwined.

Basic Analysis of Magnetic Field in High Temperature Bulk Superconductors

2007 ◽  
Vol 546-549 ◽  
pp. 2115-2118
Author(s):  
Jian Qing Yang ◽  
G.D. Chen ◽  
Xiao Yang Yuan ◽  
You Zhang Zhu
Keyword(s):  
Magnetic Field ◽  
High Temperature ◽  
Lorentz Force ◽  
Analytical Method ◽  
Critical State ◽  
Permanent Magnets ◽  
Levitation Force ◽  
Field Equations ◽  
Force Equation ◽  
Bulk Superconductors

The analysis of magnetic field in high temperature bulk superconductors is presented in this paper. The macroscopic field equations were constructed on the basis of the critical state model and levitation forces ware analyzed between permanent magnets (PM) and HTSC using analytical method. The levitation force between permanent magnets (PM) and HTSC calculation were obtained by using Lorentz force equation [1]. The analytical results show that the presented method is comparatively accurate by comparing the measured levitation forces and the calculation ones. Some relations between B(r, t) and levitation force’s hysteresis are investigated.

scholarly journals An Ideal yet Highly Accurate Model Correlating Global Average Temperature to Excess CO2-Emissions

2021 ◽  
Author(s):  
Roland Hermann Pawelke
Keyword(s):  
Transition State Theory ◽  
Ideal Gas ◽  
State Theory ◽  
Average Temperature ◽  
Global Mean Temperature ◽  
Ideal Gas Law ◽  
System Temperature ◽  
First Time ◽  
Global Mean ◽  
The Ideal

The causality of preceding atmospheric excess-to-equilibrium CO<sub>2</sub>-amounts and trailing system temperature increase is captured in terms of the ideal gas law, equilibrium thermodynamics and transition state theory for the first time: the model’s performance is excellent, publicly available global mean temperature data from 1880 (13.58 °C / 290.7 ppm) to April 2021 (14.49 °C / 416.2 ppm) are reproduced at less than ±2 % deviation. Eight future global mean temperatures for atmospheric CO<sub>2</sub>-levels between 450 ppm and 7000 ppm are extrapolated and an empiric expression of the relation is derived. The model’s ideal nature allows adaption for other greenhouse gases and provides a reference for conclusions about the energetic weighting and the wider significance of the CO<sub>2</sub>-based proportion in the total Greenhouse effect.

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