scholarly journals GRAVITATIONAL EFFECTS OF VARYING ALPHA STRINGS

2006 ◽  
Vol 21 (16) ◽  
pp. 3295-3306 ◽  
Author(s):  
J. MENEZES ◽  
C. SANTOS ◽  
P. P. AVELINO
Keyword(s):  
Scalar Field ◽  
Structure Constant ◽  
Analytical Form ◽  
Field Approximation ◽  
Weak Field ◽  
Fine Structure Constant ◽  
Type Model ◽  
Gravitational Effects ◽  
The Core ◽  
Test Particles

We study spatial variations of the fine-structure constant in the presence of static straight cosmic strings in the weak-field approximation in Einstein gravity. We work in the context of a generic Bekenstein-type model and consider a gauge kinetic function linear in the scalar field. We determine an analytical form for the scalar field and the string metric at large distances from the core. We show that the gravitational effects of α-varying strings can be seen as a combination of the gravitational effects of global and local strings. We also verify that at large distances to the core the space–time metric is similar to that of a global string. We study the motion of test particles approaching from infinity and show that photons are scattered to infinity while massive particles are trapped in bounded trajectories. We also calculate an overall limit on the magnitude of the variation of α for a GUT string, by considering suitable cosmological constraints coming from the Equivalence Principle.

A FIVE DIMENSIONAL MODEL OF EFFECTIVE GRAVITATIONAL AND FINE-STRUCTURE CONSTANTS

2002 ◽  
Vol 17 (29) ◽  
pp. 4317-4323 ◽  
Author(s):  
J. P. MBELEK ◽  
M. LACHIÈZE-REY
Keyword(s):  
Fine Structure ◽  
Scalar Field ◽  
Gravitational Constant ◽  
Structure Constant ◽  
Fine Structure Constant ◽  
Five Dimensional Model ◽  
Bulk Scalar Field ◽  
Structure Constants ◽  
Good Agreement ◽  
Kaluza Klein

It is shown that the coupling of the Kaluza-Klein (KK) internal scalar field both to an external stabilizing bulk scalar field and to the geomagnetic field may explain the observed dispersion in laboratory measurements of the (effective) gravitational constant. Except the PTB 95 value, the predictions are found in good agreement with all of the experimental data. The cosmological variation of the fine-structure constant is also addressed.

scholarly journals Accelerating universe and the time-dependent fine-structure constant

2009 ◽  
Vol 5 (H15) ◽  
pp. 302-302
Author(s):  
Yasunori Fujii
Keyword(s):  
Fine Structure ◽  
Scalar Field ◽  
Structure Constant ◽  
Theoretical Background ◽  
Point Of View ◽  
Fine Structure Constant ◽  
Time Variability ◽  
Accelerating Universe ◽  
Tensor Theory ◽  
The Right

I start with assuming a gravitational scalar field as the dark-energy supposed to be responsible for the accelerating universe. Also from the point of view of unification, a scalar field implies a time-variability of certain “constants” in Nature. In this context I once derived a relation for the time-variability of the fine-structure constant α: Δα/α =ζ Ƶ(α/π) Δσ, where ζ and Ƶ are the constants of the order one, while σ on the right-hand side is the scalar field in action in the accelerating universe. I use the reduced Planckian units with c=ℏ =MP(=(8π G)−1/2)=1. I then compared the dynamics of the accelerating universe, on one hand, and Δα/α derived from the analyses of QSO absorption lines, Oklo phenomenon, also different atomic clocks in the laboratories, on the other hand. I am here going to discuss the theoretical background of the relation, based on the scalar-tensor theory invented first by Jordan in 1955.

scholarly journals Massive Conformal Gravity

2014 ◽  
Vol 2014 ◽  
pp. 1-4 ◽  
Author(s):  
F. F. Faria
Keyword(s):  
Scalar Field ◽  
Field Approximation ◽  
Weak Field ◽  
Vacuum Field ◽  
Conformal Transformations ◽  
Conformal Gravity ◽  
Field Equations ◽  
Metric Tensor ◽  
Weak Field Approximation ◽  
Massive Theory

We construct a massive theory of gravity that is invariant under conformal transformations. The massive action of the theory depends on the metric tensor and a scalar field, which are considered the only field variables. We find the vacuum field equations of the theory and analyze its weak-field approximation and Newtonian limit.

VARIABLE SPEED OF LIGHT THEORIES: A THERMODYNAMIC ANALYSIS OF PLANETARY AND WHITE DWARF PHENOMENA

2011 ◽  
Vol 20 (05) ◽  
pp. 805-820
Author(s):  
PABLO D. SISTERNA
Keyword(s):  
Scalar Field ◽  
Time Variation ◽  
Equations Of State ◽  
Structure Constant ◽  
Hydrostatic Equilibrium ◽  
Fine Structure Constant ◽  
Variable Speed ◽  
Speed Of Light ◽  
Modified Equations ◽  
Scalar Contribution

The thermodynamics of a scalar field interacting with a perfect fluid is studied, and observable consequences of the covariant variable speed of light (VSL) theory proposed by J. Magueijo are obtained. The first law of thermodyamics is modified as the scalar field becomes an additional thermodynamical variable. A recipe to obtain the modified equations of state is also obtained. After discussing the Newtonian limit and the non-relativistic hydrostatic equilibrium equation for the theory, the time-variation of the radius of Mercury induced by the variability of the speed of light (c), and the scalar contribution to the luminosity of white dwarfs are found. Using a bound for the change of that radius and combining it with an upper limit for the variation of the fine-structure constant, a bound on the time-variation of c is set. An independent bound is obtained from luminosity estimates for Stein 2015B.

scholarly journals CONSTRAINTS ON THAWING SCALAR FIELD MODELS FROM FUNDAMENTAL CONSTANTS

2013 ◽  
Vol 22 (07) ◽  
pp. 1350035 ◽  
Author(s):  
QING GAO ◽  
YUNGUI GONG
Keyword(s):  
Fine Structure ◽  
Dark Energy ◽  
Scalar Field ◽  
Observational Data ◽  
Dark Energy Model ◽  
Structure Constant ◽  
Energy Model ◽  
Fine Structure Constant ◽  
Density Parameter ◽  
Scalar Field Models

We consider a dark energy model with a relation between the equation of state parameter w and the energy density parameter Ωϕ derived from thawing scalar field models. Assuming the variation of the fine structure constant is caused by dark energy, we use the observational data of the variation of the fine structure constant to constrain the current value of w0 and Ωϕ0 for the dark energy model. At the 1σ level, the observational data excluded some areas around w0 = –1, which explains the positive detection of the variation of the fine structure constant at the 1σ level, but ΛCDM model is consistent with the data at the 2σ level.

Δα/α FROM QSO ABSORPTION LINES DRIVEN BY AN OSCILLATING SCALAR FIELD

2005 ◽  
Vol 14 (03n04) ◽  
pp. 677-685 ◽  
Author(s):  
YASUNORI FUJII ◽  
SHUNTARO MIZUNO
Keyword(s):  
Fine Structure ◽  
Scalar Field ◽  
Structure Constant ◽  
Oscillatory Behavior ◽  
Absorption Lines ◽  
Fine Structure Constant ◽  
Time Variability ◽  
The Past

The new result on the QSO absorption lines from the VLT–UVES sample is compared with the past reports on the time-variability of the fine-structure "constant" derived from the Keck/HIRES observation, on the basis of an oscillatory behavior of the scalar field supposed to be responsible for the cosmological acceleration.

scholarly journals A Note on the Gravitoelectromagnetic Analogy

Universe ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 451
Author(s):  
Matteo Luca Ruggiero
Keyword(s):  
Slow Motion ◽  
Weak Field ◽  
Einstein’S Equations ◽  
Einstein's Equations ◽  
Gravitational Effects ◽  
Force Equation ◽  
Test Particles ◽  
Motion Approximation ◽  
Stationary Conditions ◽  
Definition Of

We discuss the linear gravitoelectromagnetic approach used to solve Einstein’s equations in the weak-field and slow-motion approximation, which is a powerful tool to explain, by analogy with electromagnetism, several gravitational effects in the solar system, where the approximation holds true. In particular, we discuss the analogy, according to which Einstein’s equations can be written as Maxwell-like equations, and focus on the definition of the gravitoelectromagnetic fields in non-stationary conditions. Furthermore, we examine to what extent, starting from a given solution of Einstein’s equations, gravitoelectromagnetic fields can be used to describe the motion of test particles using a Lorentz-like force equation.

BOUND ON THE TIME VARIATION OF THE FINE STRUCTURE CONSTANT DRIVEN BY QUINTESSENCE

2005 ◽  
Vol 14 (02) ◽  
pp. 335-343 ◽  
Author(s):  
DA-SHIN LEE ◽  
WOLUNG LEE ◽  
KIN-WANG NG
Keyword(s):  
Fine Structure ◽  
Scalar Field ◽  
Time Variation ◽  
Structure Constant ◽  
Fine Structure Constant ◽  
Fifth Force

The bound on the time variation of the fine structure constant (α) driven by the dynamics of quintessence scalar field which is coupled to electromagnetism is discussed using phenomenological quintessential models constrained by SNIa and CMB observations. We find that those models allowing early quintessence give the largest variation Δα at the decoupling epoch. Furthermore, the fifth force experiments imply that Δα/α is less than about 0.1%.

scholarly journals BIMETRIC GRAVITY THEORY, VARYING SPEED OF LIGHT AND THE DIMMING OF SUPERNOVAE

2003 ◽  
Vol 12 (02) ◽  
pp. 281-298 ◽  
Author(s):  
J. W. MOFFAT
Keyword(s):  
Scalar Field ◽  
Structure Constant ◽  
Friedmann Equation ◽  
Gravitational Theory ◽  
Fine Structure Constant ◽  
Speed Of Light ◽  
Dark Energy Component ◽  
Bimetric Gravity ◽  
Physical Consequences ◽  
The Universe

In the bimetric scalar–tensor gravitational theory there are two frames associated with the two metrics ĝμν and gμν, which are linked by the gradients of a scalar field ϕ. The choice of a comoving frame for the metric ĝμν or gμν has fundamental physical consequences for local observers in either metric spacetimes, while maintaining diffeomorphism invariance. If the metric gμν is chosen to be associated with comoving coordinates, then the speed of light varies in the frame with the metric ĝμν. Observers in this frame see the dimming of supernovae because of the increase of luminosity distance versus red shift, due to an increasing speed of light in the past universe. Moreover, in this frame the scalar field ϕ describes a dark energy component in the Friedmann equation for the cosmic scale without acceleration. If we choose ĝμν to be associated with comoving coordinates, then an observer in the gμν metric frame will observe the universe to be accelerating and the supernovae will appear to be farther away. The theory predicts that the gravitational constant G can vary in spacetime, while the fine-structure constant α = e2/ℏc does not vary. The problem of cosmological horizons as viewed in the two frames is discussed.

scholarly journals SPACETIME VARIATION OF α AND THE CMB POWER SPECTRA AFTER THE RECOMBINATION

2011 ◽  
Vol 26 (01) ◽  
pp. 43-52 ◽  
Author(s):  
XIULIAN WANG ◽  
MINGZHE LI
Keyword(s):  
Fine Structure ◽  
Scalar Field ◽  
Power Spectra ◽  
Structure Constant ◽  
Fine Structure Constant ◽  
Microwave Background ◽  
Minimal Coupling ◽  
Spatial Fluctuation ◽  
Light Scalar ◽  
Dynamical Nature

The possible variation of the fine structure constant may be due to the non-minimal coupling of the electromagnetic field to a light scalar field which can be the candidate of dark energy. Its dynamical nature renders the fine structure constant varies with time as well as space. In this paper we point out that the spatial fluctuation of the fine structure will modify the power spectra of the temperature and the polarization of the cosmic microwave background. We show explicitly that the fluctuations of the coupled scalar field generate new temperature anisotropies at the linear order and induce a B mode to the polarization at higher order in general.

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