scholarly journals DOPPLER EFFECTS FROM BENDING OF LIGHT RAYS IN CURVED SPACE–TIMES

2006 ◽  
Vol 15 (08) ◽  
pp. 1183-1198
Author(s):  
MATTEO LUCA RUGGIERO ◽  
ANGELO TARTAGLIA ◽  
LORENZO IORIO
Keyword(s):  
Gravitational Field ◽  
Quadrupole Moment ◽  
Giant Planets ◽  
Axially Symmetric ◽  
Curved Space ◽  
Gravitational Fields ◽  
Light Rays ◽  
Doppler Effects ◽  
Electromagnetic Signals ◽  
Bending Of Light

We study Doppler effects in curved space–time, i.e. the frequency shifts induced on electromagnetic signals propagating in the gravitational field. In particular, we focus on the frequency shift due to the bending of light rays in weak gravitational fields. We consider, using the PPN formalism, the gravitational field of an axially symmetric distribution of mass. The zeroth order, i.e. the sphere, is studied then passing to the contribution of the quadrupole moment, and finally to the case of a rotating source. We give numerical estimates for situations of physical interest, and by a very preliminary analysis, we argue that analyzing the Doppler effect could lead, in principle, in the foreseeable future, to the measurement of the quadrupole moment of the giant planets of the Solar System.

MOTION AROUND A GLOBAL MONOPOLE

2000 ◽  
Vol 15 (06) ◽  
pp. 869-873
Author(s):  
A. BANERJEE ◽  
T. GHOSH
Keyword(s):  
Gravitational Field ◽  
Einstein Equations ◽  
Global Monopole ◽  
Test Particles ◽  
Light Rays ◽  
Bending Of Light

The motion of test particles and light rays in the perturbed gravitational field around a global monopole is studied. The metric of the monopole was previously obtained by solving the linearized semiclassical Einstein equations (Hiscock). The bending of light ray passing by such a monopole has contributions from the conical object as well as from the perturbed terms. The possibility of trapping particles in the perturbed gravitational field is also discussed.

scholarly journals Approximate perfect fluid solutions with quadrupole moment

2021 ◽  
Author(s):  
Medeu Abishev ◽  
Nurzada Beissen ◽  
Farida Belissarova ◽  
Kuantay Boshkayev ◽  
Aizhan Mansurova ◽  
...  
Keyword(s):  
Perfect Fluid ◽  
Quadrupole Moment ◽  
Line Element ◽  
Approximate Solutions ◽  
Axially Symmetric ◽  
Field Equations ◽  
Matching Conditions ◽  
Fluid Source ◽  
Gravitational Fields ◽  
Spherically Symmetry

We investigate the interior Einstein’s equations in the case of a static, axially symmetric, perfect fluid source. We present a particular line element that is specially suitable for the investigation of this type of interior gravitational fields. Assuming that the deviation from spherically symmetry is small, we linearize the corresponding line element and field equations and find several classes of vacuum and perfect fluid solutions. We find some particular approximate solutions by imposing appropriate matching conditions.

scholarly journals Possible Alterations of Local Gravitational Field Inside a Superconductor

Entropy ◽  
2021 ◽  
Vol 23 (2) ◽  
pp. 193 ◽  
Author(s):  
Giovanni Alberto Ummarino ◽  
Antonio Gallerati
Keyword(s):  
Gravitational Field ◽  
Landau Theory ◽  
Time Dependent ◽  
Qualitative Comparison ◽  
Ginzburg Landau ◽  
High Tc ◽  
Gravitational Fields ◽  
Favorable Conditions

We calculate the possible interaction between a superconductor and the static Earth’s gravitational fields, making use of the gravito-Maxwell formalism combined with the time-dependent Ginzburg–Landau theory. We try to estimate which are the most favorable conditions to enhance the effect, optimizing the superconductor parameters characterizing the chosen sample. We also give a qualitative comparison of the behavior of high–Tc and classical low–Tc superconductors with respect to the gravity/superfluid interplay.

scholarly journals PARAMETRIC INSTABILITY IN SCALAR GRAVITATIONAL FIELDS

2012 ◽  
Vol 27 (24) ◽  
pp. 1230023 ◽  
Author(s):  
TREVOR B. DAVIES ◽  
CHARLES H.-T. WANG ◽  
ROBERT BINGHAM ◽  
J. TITO MENDONÇA
Keyword(s):  
Gravitational Field ◽  
Field Effect ◽  
Strong Field ◽  
Parametric Instability ◽  
Spherically Symmetric ◽  
Scalar Tensor Theory ◽  
Subsequent Work ◽  
Dynamical Mechanism ◽  
Gravitational Fields ◽  
Tensor Theory

We present a brief review on a new dynamical mechanism for a strong field effect in scalar–tensor theory. Starting with a summary of the essential features of the theory and subsequent work by several authors, we analytically investigate the parametric excitation of a scalar gravitational field in a spherically symmetric radially pulsating neutron star.

Numerical Analysis of Air Convection in a Vertical Cylindrical Container With and Without a Gravitational Field Under a Gradient of a Magnetic Field

2002 ◽  
Author(s):  
Masato Akamatsu ◽  
Mitsuo Higano ◽  
Yoshio Takahashi ◽  
Hiroyuki Ozoe
Keyword(s):  
Magnetic Field ◽  
Gravitational Field ◽  
Transfer Rate ◽  
Relative Orientation ◽  
Axial Position ◽  
Cylindrical Container ◽  
Gravitational Fields ◽  
Air Convection ◽  
Magnetizing Force ◽  
The Magnetic Field

Two-dimensional numerical computations were carried out for natural convection of air in a vertical cylindrical container with and without a gravitational field under a gradient of a magnetic field. The magnetic field and the magnetizing force were induced in the cylinder area and the strength and the vectors of the magnetizing force were dependent on the axial location of the electric coil. Sample computations were carried out by changing the relative orientation of an electric coil and container. In a gravitational field, air in a cylindrical container was driven by both gravitational and magnetizing forces. On the other hand, the air flow was induced by the magnetizing force even in a non-gravitational field. Flow pattern and the heat transfer rate greatly depended on the axial position of the electric coil under both gravitational and non-gravitational fields.

scholarly journals Gravitational Fields and Gravitational Waves

2021 ◽  
Author(s):  
Tony Yuan
Keyword(s):  
Gravitational Field ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Doppler Effect ◽  
Gravitational Force ◽  
Laser Interferometer ◽  
Speed Of Light ◽  
Gravitational Fields ◽  
Light Waves ◽  
Research Questions

The relative velocity between objects with finite velocity affects the reaction between them. This effect is known as general Doppler effect. The Laser Interferometer Gravitational-Wave Observatory (LIGO) discovered gravitational waves and found their speed to be equal to the speed of light c. Gravitational waves are generated following a disturbance in the gravitational field; they affect the gravitational force on an object. Just as light waves are subject to the Doppler effect, so are gravitational waves. This article explores the following research questions concerning gravitational waves: What is the spatial distribution of gravitational waves? Can the speed of a gravitational wave represent the speed of the gravitational field (the speed of the action of the gravitational field upon the object)? What is the speed of the gravitational field? Do gravitational waves caused by the revolution of the Sun affect planetary precession? Can we modify Newton’s gravitational equation through the influence of gravitational waves?

scholarly journals Generalizing the coupling between geometry and matter: $$f\left( R,L_m,T\right) $$ gravity

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Zahra Haghani ◽  
Tiberiu Harko
Keyword(s):  
Gravitational Field ◽  
Energy Momentum Tensor ◽  
Equations Of Motion ◽  
Momentum Tensor ◽  
Newtonian Limit ◽  
Gravity Models ◽  
Momentum Balance ◽  
Field Equations ◽  
Gravitational Fields ◽  
Generalized Poisson

AbstractWe generalize and unify the $$f\left( R,T\right) $$ f R , T and $$f\left( R,L_m\right) $$ f R , L m type gravity models by assuming that the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar R, of the trace of the energy–momentum tensor T, and of the matter Lagrangian $$L_m$$ L m , so that $$ L_{grav}=f\left( R,L_m,T\right) $$ L grav = f R , L m , T . We obtain the gravitational field equations in the metric formalism, the equations of motion for test particles, and the energy and momentum balance equations, which follow from the covariant divergence of the energy–momentum tensor. Generally, the motion is non-geodesic, and takes place in the presence of an extra force orthogonal to the four-velocity. The Newtonian limit of the equations of motion is also investigated, and the expression of the extra acceleration is obtained for small velocities and weak gravitational fields. The generalized Poisson equation is also obtained in the Newtonian limit, and the Dolgov–Kawasaki instability is also investigated. The cosmological implications of the theory are investigated for a homogeneous, isotropic and flat Universe for two particular choices of the Lagrangian density $$f\left( R,L_m,T\right) $$ f R , L m , T of the gravitational field, with a multiplicative and additive algebraic structure in the matter couplings, respectively, and for two choices of the matter Lagrangian, by using both analytical and numerical methods.

MULTI-SCALE MECHANICAL BEHAVIOR ANALYSIS ON FLUID–SOLID COUPLING FOR OSTEONS IN VARIOUS GRAVITATIONAL FIELDS

2021 ◽  
Author(s):  
HAO ZHANG ◽  
HAI-YING LIU ◽  
CHUN-QIU ZHANG ◽  
ZHEN-ZHONG LIU ◽  
WEI WANG
Keyword(s):  
Gravitational Field ◽  
Fluid Shear Stress ◽  
Bone Matrix ◽  
Fluid Pressure ◽  
Gravity Gradient ◽  
Static Compression ◽  
Gravitational Fields ◽  
Multi Scale ◽  
Earth’S Gravitational Field ◽  
Mechanical Microenvironment

Background: Compact bone mainly consists of cylindrical osteon structures. In microgravity, the change in the mechanical microenvironment of osteocytes might be the root cause of astronauts’ bone loss during space flights. Methods: A multi-scale three-dimensional (3D) fluid–solid coupling finite element model of osteons with a two-stage pore structure was developed using COMSOL software based on the natural structure of osteocytes. Gradients in gravitational fields of [Formula: see text]1, 0, 1, 2.5, and 3.7[Formula: see text]g were used to investigate the changes in the mechanical microenvironment on osteocyte structure. The difference in arteriole pulsating pressure and static compression stress caused by each gravity gradient was investigated. Results: The mechanical response of osteocytes increased with the value of g, compared with the Earth’s gravitational field. For instance, the fluid pressure of osteocytes and the von Mises stress of bone matrix near lacunae decreased by 31.3% and 99.9%, respectively, in microgravity. Under static loading, only about 16.7% of osteocytes in microgravity and 58.3% of osteocytes in the Earth’s gravitational field could reach the fluid shear stress threshold of biological reactions in cell culture experiments. Compared with the Earth’s gravitational field, the pressure gradient inside osteocytes severely decreased in microgravity. Conclusion: The mechanical microenvironment of osteocytes in microgravity might cause significant changes in the mechanical microenvironment of osteocytes, which may lead to disuse osteoporosis in astronauts.

3. Extrasolar tests of gravity

2017 ◽  
pp. 35-45
Author(s):  
Timothy Clifton
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Field ◽  
Solar System ◽  
Neutron Stars ◽  
Event Horizon ◽  
Gravitational Fields ◽  
Binary Pulsars ◽  
Tests Of Gravity ◽  
Triple Star

By studying objects outside our Solar System, we can observe star systems with far greater gravitational fields. ‘Extrasolar tests of gravity’ considers stars of different sizes that have undergone gravitational collapse, including white dwarfs, neutron stars, and black holes. A black hole consists of a region of space-time enclosed by a surface called an event horizon. The gravitational field of a black hole is so strong that anything that finds its way inside the event horizon can never escape. Other star systems considered are binary pulsars and triple star systems. With the invention of even more powerful telescopes, there will be more tantalizing possibilities for testing gravity in the future.

Sign in / Sign up

Export Citation Format

Share Document