Tagged Questions
0
votes
0answers
87 views
covarient derivative of electromagnetic field tensor
I'm trying to prove the energy momentum tensor in curved spacetime for Electromagnetic field is Divergence-less directly(Without using general lie derivative method which can prove any energy momentum ...
0
votes
2answers
131 views
Advanced Heaviside-Feynman formula implies electromagnetic inertia?
The Heaviside-Feynman formula (see Feynman Lectures vol I Ch.28, vol II Ch. 21) gives the electric and magnetic fields measured at an observation point $P$ due to an arbitrarily moving charge $q$
$$ ...
1
vote
2answers
108 views
Are electrons moving? If so relative to whom? and why is there no magnetic field?
electrons on earth moving with us, due to rotation of earth, revolution of earth, sun and our galaxy right?
Then, why is there no magnetic field around a piece of copper wire?
1
vote
1answer
50 views
Regarding Electromagnetic Plane and Maxwell equations
I asked this on the math.stackechange but I was told that it might be a good idea to ask here too since my problem is physics/math! Here is the question:
Hello everybody I am kind of struggling with ...
1
vote
0answers
73 views
Einstein +Maxwell 's tensor
Why is it true that we can deduce that Einstein's GR equations coupled with Maxwell's EM equations may be written in the form $$R_{ij}=C(F_{ik}F_j^{\,\,k}-{1\over 4}g_{ij}F_{mn}F^{mn})$$
without ...
4
votes
2answers
240 views
Einstein Field Equations and Electromagnetic Stress-Energy Tensor
My question is: if we write Einstein field equations in this form:
$$R_{\mu\nu} - \dfrac{1}{2}g_{\mu\nu}R=8\pi \dfrac{G}{c^4}T_{\mu\nu}$$
Then the left hand side is one statement about the geometry ...
1
vote
3answers
243 views
Similarity between the Coulomb force and Newton's gravitational force
Coulomb force and gravitational force has the same governing equation. So they should be same in nature. A moving electric charge creates magnetic field, so a moving mass should create some force ...
4
votes
2answers
174 views
Does Kaluza-Klein Theory Require an Additional Scalar Field?
I've seen the Kaluza-Klein metric presented in two different ways., cf. Refs. 1 and 2.
In one, there is a constant as well as an additional scalar field introduced:
$$\tilde{g}_{AB}=\begin{pmatrix}
...
4
votes
4answers
313 views
Can a photon get emitted without a receiver?
It is generally agreed upon that electromagnetic waves from an emitter does not have to connect to a receiver, but how can we be sure this is a fact? The problem is that we can never observe non ...
4
votes
1answer
121 views
Kaluza-Klein Christoffel Symbols
I have a question regarding the connection coefficients as they pertain to the following paper: http://www.weylmann.com/kaluza.pdf . When I try to calculate the 4D Christoffel symbols from the 4D part ...
3
votes
0answers
79 views
Materials with different gravitomagnetic permeability?
If you start with general relativity, and assume small perturbations around a nearly flat metric, it is possible to obtain linearized equations of gravity that look a lot like Maxwell's equations, ...
3
votes
3answers
301 views
Gravity stronger than electromagnetic force in a black hole?
Well, the question has somewhat been answered before, but there's one part missing, which - I'd think - is in conflict with the physical laws.
The earlier reply says that the gravitational pull even ...
9
votes
1answer
408 views
If you are carrying a magnet, can you tell when you cross the event horizon of a black hole?
By the no hair theorem, a black hole is completely characterized by it's mass, charge and angular momentum. Therefore dipole and higher pole magnetic fields are completely expelled when a black hole ...
8
votes
0answers
289 views
Do intergalactic magnetic fields imply an Open Universe?
According to a recent paper on the arXiv, they do. How credible is this result? The abstract says:
The detection of magnetic fields at high redshifts, and in empty
intergalactic space, support ...
3
votes
1answer
153 views
If a magnetic monopole falls into a schwarzchild black hole, what happens to the magnetic field?
By the no-hair theorem, black holes can only have mass, charge and angular momentum. Does "charge" include "magnetic charge" (such as from a magnetic monopole)? Can black holes have magnetic charge ...
6
votes
1answer
202 views
When a neutral star with a magnetic field collapses to form a black hole, what happens to the magnetic field?
By the no-hair theorem, black holes are only characterized by mass, charge and angular momentum. If the star is neutral, the black hole will have only mass and angular momentum - and therefore it ...
6
votes
1answer
199 views
What happens to an embedded magnetic field when a black hole is formed from rotating charged dust?
Black holes have no-hair so there are uniquely specified by a mass, charge and angular momentum. Imagine a cloud of charged rotating dust. There will be a magnetic field associated with the current ...
2
votes
4answers
1k views
If gravity is a bend in Space-time then what is magnetism?
Einstein postulated that gravity bends the geometry of space-time then what does magnetism do in to the geometry of space-time, or is there even a correlation between space-time geometry and ...
2
votes
1answer
141 views
Can a charged black hole interact via electromagnetism? [duplicate]
Possible Duplicate:
Detection of the Electric Charge of a Black Hole
Light cannot escape from a black hole. However light is also interpreted as the carrier of the electromagnetic force. So ...
0
votes
1answer
176 views
Gravimagnetic monopole and General relativity
Review and hystorical background:
Gravitomagnetism (GM), refers to a set of formal analogies between Maxwell's field equations and an approximation, valid under certain conditions, to the Einstein ...
2
votes
1answer
318 views
is space infinitely divisible?
As a child I remember hearing the popular paradox presented by Zeno proposing that Achilles could never catch a tortoise in a race since he would have to traverse the infinite space between himself ...
1
vote
1answer
297 views
Blandford-Znajek process: Why/how does the current flow along the magnetic field lines
Related: How would a black hole power plant work?
I have put a bit of commentary enumerating my confusions in parentheses
I read in Black Holes and Time Warps (Kip Thorne), that quasars can generate ...
0
votes
2answers
167 views
Should $E$ and $B$ change with Gravity?
Lets examine a typical GR metric:
$$ds^2=g_{00}dt^2-g_{11}dx^2-g_{22}dy^2-g_{33}dz^2$$
The "d" going with ds has its correct meaning when the path is
specified with respect to a one dimensional ...
5
votes
2answers
84 views
Torsion and gauge invariant EM kinetic term
Everytime I hear about adding torsion to GR, something struggles me: how do you create a kinetic term for the electromagnetic field that is still gauge-invariant? One of the consequences of torsion is ...
3
votes
3answers
569 views
Action principle for the Electromagnetism and Gravity
Here is the formula for the stress energy tensor:
$$
T_{\mu\nu} = - {2\over\sqrt{ |\det g| }}{\delta S_{EM}\over
\delta g^{\mu\nu}}
$$
(This follows from varying the total action $S ...
2
votes
1answer
165 views
What determine whether the dynamical equations are tensor equations or vector equations?
Newton's 2nd law which is central to Newtonian dynamics, is a vector equation
$\sum\textbf{F}_{external}=m\textbf{a}$
Same with Maxwell's equations in the covariant form.
On the other hand, ...
6
votes
3answers
338 views
Charging a black hole?
What would happen if we have a black hole and we start shooting at it a single electron at a time, and go on doing it forever? Would the electrons start to bounce off eventually?
3
votes
2answers
428 views
What role does electrical charge play in black holes?
Not having studied General Relativity, I have sometimes been puzzled by references to the behaviour for "classic" black holes — as they are popularly portrayed — as being true for black ...
13
votes
2answers
400 views
Detection of the Electric Charge of a Black Hole
By the "No Hair Theorem", three quantities "define" a black hole; Mass, Angular Momentum, and Charge. The first is easy enough to determine, look at the radius of the event horizon and you can use the ...
3
votes
3answers
241 views
Singularity-free stationary electro-vacuum solution
Let's say we have a spherically symmetric fluid:
$$
T^{\alpha \beta} = \begin{bmatrix}
\rho & 0 & 0 & 0 \\
0 & p & 0 & 0 \\
0 & 0 & p & 0 \\
0 ...
3
votes
2answers
250 views
Gravitational wave energy
Electromagnetic energy can be related to it's frequency via $E=h\nu$. Is there a comparable relationship between gravitational wave energy and frequency?
18
votes
5answers
658 views
Should a neutron fall faster than a proton?
If you drop a proton and a neutron in a gravitational field, they both fall, but the proton has a charge and accelerating charges radiate energy, so that leaves less kinetic energy for the proton and ...
13
votes
7answers
2k views
Is it theoretically possible to shield gravitational waves?
Electromagnetic waves can be shielded by a perfect conductor. What about gravitational waves?
4
votes
2answers
549 views
Noticing that Newtonian gravity and electrostatics are equivalent, is there also a relationship between the general relativity and electrodynamics?
In classical mechanics, we had Newton's law of gravity $F \propto \frac{Mm}{r^2}$. Because of this, all laws of classical electrostatics applied to classical gravity if we assumed that all charges ...
3
votes
3answers
835 views
Is it possible/correct to describe electromagnetism using curved space(-time)?
Comparing the simples form of the forces of both phenomena: the law of Newton for gravitation $V\propto \frac{1}{r}$, and the Coulomb law for electrostatics $V\propto \frac{1}{r}$, one might think ...
