The special theory of relativity describes the motion and dynamics of objects moving at significant fractions of the speed of light.
5
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2answers
157 views
Relativistic equivalent of a spring-force?
Usually what helps me understand a concept better in physics is to write a simulation of it. I've got to the point where I'm competent in the basics of special relativity, but, I can't figure out how ...
1
vote
2answers
86 views
What is the process that gives mass to free relativitic particles?
When a free particle move in space with a known momentum and energy then what is the physical process that gives mass to that free (relativistic) particle?
What is role does the Higgs field in that ...
1
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2answers
274 views
Special Relativity: What differential equation describes an accelerated object from a non-inertial reference frame?
I am looking for a set of differential equations (to be solved numerically for an educational program) that would describe the position and apparent time of an accelerated clock relative to a ...
6
votes
1answer
195 views
drift velocity of electrons in a superconductor
is there a formula for the effective speed of electron currents inside superconductors?
The formula for normal conductors is:
$$ V = \frac{I}{nAq}$$
I wonder if there are any changes to this ...
2
votes
1answer
55 views
Relativistic Computation?
Is it possible to employ relativity to develop computational technology?
Here is a really basic example:
Build a Computer and Feed it the Problem (say the problem is projected to take 10 years to ...
2
votes
1answer
50 views
Field Tensor and classical limits
I would be very grateful if someone would kindly explain this generalization of the Lorentz force law to the special relativity domain. Please bear with me.
Classically, the Lorentz force law is ...
2
votes
1answer
67 views
Understanding bending light beam perpendicular to motion
I'm just reading a book about gravity. An example it gives is a spaceship accelerating. A beam of light travelling at right angles to the direction of movement of the spaceship enters it via a small ...
1
vote
1answer
78 views
The definition of Lorentz transformation
I know that the Lorentz transformation, when two frames $\mathcal{S}$ and $\mathcal{S}'$ are in standard configuration (the axes are all parallel to their counterparts in the other inertial frame) is ...
1
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1answer
88 views
Retarded time Lienard Wiechert potential
In a potential which needs to be evaluated at the retarded time, is this the time which represents the actual time the "physics" occurred? So $t_{\text{ret}}=t-\frac{r}{c}$, not just because it may be ...
1
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1answer
201 views
Special relativity paradox and gravitation/acceleration equivalence
One of the features of the black hole complementarity is the following :
According to an external observer, the infinite time dilation at the horizon itself makes it appear as if it takes an ...
1
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1answer
194 views
Why can't this speed be measured?
Superman and Supergirl were playing catch. When Superman is moving with a speed of 0.800c relative to Supergirl, he threw a ball to Supergirl with a speed of 0.600c relative to him.
a. ...
0
votes
1answer
39 views
Relativistic Lagrangian transformations
I need to study the relativistic lagrangian of a free particle.
It's
$\ L= - m c^2 \sqrt[2]{1- \frac{|u|^2}{c^2}} $ I need to study the translation, boost and rotation symmetry. I say it doesn't ...
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votes
1answer
26 views
Viewing a reference frame from inside of it?
Can one observe one's own frame of reference without moving out side the frame?
For example, if you are on a train and you throw ball in the air up and down.
When you are on the train (frame 1) you ...
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votes
1answer
45 views
Wavefront emitted by bodies at traveling near the velocity of light
I studied that no body can travel with the velocity of light. But, assuming that when a body moves nearly velocity of light, will it obey length contraction law of Einstein or will it emit the same ...
0
votes
1answer
74 views
What's the relativistic energy of a moving strained spring as $k\to\infty$
Suppose a spring with stiffness $k$, is strained by constant forces on each end.
In a frame where the strained spring moves at a constant velocity, what's the total relativistic energy of the moving ...
0
votes
1answer
124 views
Why does weak equivalence principle say gravity is equivalent to acceleration?
I am told that the weak equivalent principle, that $m_i=m_g$ (inertial and gravitational masses are equivalent) is equivalent to the statement that in a small system you can't tell whether you are in ...
-1
votes
1answer
73 views
Speed astronauts measure moving at the speed of light
Lets suppose a spaceship travels with v = 0.9c relative to the Earth. The time inside the spaceship would pass slower than on Earth. Would the astronauts measure a different speed (that means, a ...
-6
votes
1answer
197 views
Speed of light is not fixed?
In my research, I found that the speed of light is not fixed. IS it true?
Namely, We know that light refracts when the medium it travels through changes. Actually, light travels in the same medium ...
6
votes
0answers
89 views
Status of experimental searches for tachyons?
Now that the dust has settled on the 2011 superluminal neutrino debacle at OPERA, I'm interested in understanding the current status of experimental searches for neutrinos. Although the OPERA claim ...
5
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0answers
62 views
Why do we identify symmetric 2nd rank tensors with spin-2 particles in string theory?
I am going through Tong's lecture notes on String Theory and came across the following irrep decomposition (Chap 2, p.43) of the bosonic string first excited states:
$$\text{traceless symmetric} ...
5
votes
0answers
157 views
What is the difference between the properties of Electron spin and Photon polarization/helicity?
What is the difference between a photon's polarization/helicity and an electrons spin half? I know that the photon is spin 1 but isn't its polarization analogous to spin half?
This question stems ...
4
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0answers
87 views
What is the proper time used in relativistic non equilibrium statistical physics?
In the literature one often finds covariant relativistic generalizations of classical non equilibrium statistical equations (Boltzmann, Vlasov, Landau, fokker-planck, etc...) but I wonder what is the ...
3
votes
0answers
28 views
What's wrong with this application of Thomas Precession to circular motion velocity measurements?
If you happen to have the Third Edition of Classical Electrodynamics by John David Jackson, turn to section 11.8, as that's where I'm getting all this from. If not, you should still be able to follow ...
3
votes
0answers
103 views
Meaning of spin
I'm pretty astounded that I did not hear about this sooner, but in my course on QFT our professor told us that the concept of spin can be used to mean three things:
Mechanical spin (apparently a ...
3
votes
0answers
138 views
Should the Jacobian be negative in $\mathrm{d}^4 x$?
In page 24 of Srednicki's QFT textbook, he says that $\mathrm{d}^4x$ is a Lorentz scalar. I understand that the determinant of a Lorentz matrix is always $\pm 1$. So in an improper Lorentz ...
3
votes
0answers
78 views
How would an observer perceive movement on a train that's travelling near the speed of light?
Person A is on Earth and a train (or whatever you want to imagine) travels past him at near the speed of light. How would person A perceive movement on the ship? If time is slowed on the ship from the ...
3
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0answers
41 views
Spectrum of a quantum relativistic “distance squared” operator
This question disusses the same concepts as that question (this time in quantum context). Consider a relativistic system in spacetime dimension $D$. Poincare symmetry yields the conserved charges $M$ ...
2
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0answers
75 views
Fermi Walker vs. Fermi transport
A vector field $f^\mu$ is said to be Fermi-Walker transported along a curve $\gamma$ parametrized with $\tau$ if the following holds $$\frac{\mathrm{D}}{\mathrm{d}\tau}f^\mu = -(a^\mu v^\nu - a^\nu ...
2
votes
0answers
75 views
Car parking special-relavity puzzle
Hi I read the following puzzle from an old text book long time ago. However it doesn't provide the answer. So what is the solution?
Let's suppose a car is going to park to a garage and the garage is ...
2
votes
0answers
117 views
How do I extend the Lorentz transformation metric to dimensions>4?
How do I extend the general Lorentz transformation matrix (not just a boost along an axis, but in directions where the dx1/dt, dx2/dt, dx3/dt, components are all not zero. For eg. as on the Wikipedia ...
2
votes
0answers
87 views
Does the passage of time effect a photons entanglement with another?
I recently read an article about "Delayed-choice entanglement swapping". Here is an excerpt from the article:
Delayed-choice entanglement swapping consists of the following steps.
(I use the ...
1
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0answers
43 views
Solving the equation of relativistic motion
How does one solve the tensor differential equation for the relativistic motion of a partilcle of charge $e$ and mass $m$, with 4-momentum $p^a$ and electromagnetic field tensor $F_{ab}$ of a constant ...
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0answers
149 views
Does Mansuripur's Paradox involve fictitious charges?
Mansuripur's Paradox involves a magnet moving at relativistic speeds in an external electric field.
Additional: thanks to Retarded Potential, who found the original paper.
If I understand correctly, ...
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0answers
160 views
Matrix manipulation for Dirac matrices
From the Dirac equation in gamma matrices, we know that $$\gamma^i=\begin{pmatrix}
0 & \sigma^i \\
-\sigma^i & 0
\end{pmatrix}$$ and $$\gamma^0=\begin{pmatrix}
I & 0 \\
0 & -I
...
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0answers
40 views
Adittional ways of writing down the gamma in relation to speen direction
I have managed to proove below that equation $\gamma(v')=\gamma \gamma(v)\left(1-v_x \, u\!/\!c^2\right)$ holds if whole speed $v$ is in the direction of axis $x,x'$. So $v$ equals $v_x$ and therefore ...
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0answers
200 views
Could someone transmit a signal with equally-tuned Casimir plates across the quantum field?
It seems, one could exploit the Casimir effect to send messages across arbitrarily-large distances with carefully-tuned Casimir plates.
Obviously, relativity would preclude FTL information transfer, ...
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0answers
239 views
How equivalent are heat energy and work energy in connection with a spinning flywheel?
Let's say we have two identical spinning flywheels, that have arbitrary geometry, and are made of copper.
Now we apply some heat energy at the center point of flywheel A, causing it to slow down a ...
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0answers
57 views
Relativistic canonical transformation
What is relativistic canonical transformation? I need every piece of information about it.
Does anyone know a reference or an article about relativistic canonical transformation?
For example, in ...
0
votes
0answers
40 views
Relativistic solution for Zeno's stadium paradox?
The stadium Zeno paradox (not the same paradox from the Quantum-Zeno-Effect, but the same Zeno) gives a paradox about time, when two runners move toward a standing person from different directions. ...
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0answers
64 views
Relativistic interaction: gamma + proton = delta
We have a proton at rest, and there's an incident photon that is absorbed by the proton producing the excited state "delta".
Photon energy: $\hbar \omega$,
Proton rest Energy: $m_p c^2$,
Delta rest ...
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0answers
103 views
About the theory of relativity
Why is speed of light constant in every non inertial frame of reference? Is there any theoretical explanation behind this postulate Since we cannot completely depend upon the experimental results?
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0answers
83 views
Alternate derivation of kinetic mass increase in special relativity, from Maudlin
I've recently come across a derivation, which I've not seen before, of mass increase in special relativity. It seems to make sense, but I get tripped-up on an intermediate step, and I can't seem to ...
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0answers
31 views
time oscillation
Can there be a situation, where the time dilation is oscillating, in the sense that one observer notes that the time for the other frame is moving faster then slower, etc...? Can this oscillation be ...
0
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0answers
70 views
Proper time and 4-velocity
I am trying to derive 4-velocity, but i get stucked when i try to derive equation for proper time. I end up confused as i get $\scriptsize\textrm{d}\tau = \frac{\textrm{d}t}{\gamma(v)}$ instead of ...
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0answers
42 views
Help identifying an expression for the action
I found the following expression for the action of a (free, I think) relativistic particle in my notes but I can't remember from what it came from:
$$ S = \int_{0}^{N} \left [ ...
0
votes
0answers
187 views
Is there an easy derivation of relativistic velocities addition and relativistic doppler shift?
Is there an easy derivation of relativistic velocities addition and relativistic doppler shift?
I'm looking for some easy derivation of the above. Like this ...
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0answers
18 views
Is there a way to compute or explain if a decay prefers decaying into mainly mass or mainly energy?
Is there a way to compute or explain if a decay prefers decaying into mainly mass or mainly energy ?
I know quarks prefer to decay into the most massfull quarks : ...
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0answers
143 views
Newton Gravitational constant $G$, Plank constant $\hbar$ , Speed of Light $c$ : The Dream Team of moderators?
The 3 great constants of Nature are well known :
The Speed of light $c$ (special relativity)
The Plank constant $\hbar$ (quantum mechanics)
The Newton ...
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0answers
157 views
Lorentz transformations of the polarization vector
Let $\bf{n}'$ be a unit vector in the direction of a wavevector in the plasma rest frame and $\bf{B'}$ be a unit vector along the magnetic
field in the plasma rest frame. The electric field of a ...
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0answers
153 views
Comparing Lagrangian in Special Relativity vs General Relativity for a weak gravitational field
This is a sequel to this question.
Who knows a difference between the Lagrangian in SR and GR for a weak gravitational field in non-relativistic case? What is the reason of this difference?
