All Questions
12,537 questions
0
votes
2
answers
51
views
Order of events is invariant in timelike intervals
I thought that the order of events could be something that changes with a boost. But recently, I read in a book that for time-like separated events, the order of events is invariant.
If I think about ...
3
votes
2
answers
96
views
Validity of the velocity addition formulae in Special Relativity using the four-velocity
I'm an undergrad who takes an undergrad SR course and in one of our homework we are asked to find the velocity addition formulae not using the Lorentz transformations but using the four-velocity and ...
- 55
1
vote
1
answer
43
views
Confinement energy scale and boosts
Imagine a reference system where a certain proton is standing still in front of us. We measure its energy and we realize it's very low, so that the strong coupling constant $\alpha_s$ is pretty high ...
- 11
0
votes
0
answers
59
views
Is a quantum state lorentz covariant?
Quantum states are defined on a equal-time time slice. However, an equal-time slice is not an equal-time slice for another boosted frame. So in order for formulation of quantum theory to be Lorentz ...
- 133
-2
votes
0
answers
119
views
Find a "paradox" in QFT where you can identify an absolute frame of reference, please point out errors in my reasoning
I'm not an amateur and I learned QFT systematically. This paradox just occurred to me out of nowhere.
The principle of SR tells us that the law of physics should look the same in all inertial frame. ...
- 133
1
vote
0
answers
55
views
Does the radial wavefunction of the Hydrogen Atom have a relativistic correction?
Fairly simple question but I have not found a definite answer for. With the Schrodinger equation solution for the Hydrogen atom there are higher-order energy corrections which need to be tacked on to ...
- 113
2
votes
1
answer
97
views
Are we sure photons are particles, given that a 1 Hz photon is bigger than our planet? [duplicate]
A photon of 1 Hz has a wavelength of 300000 km, making it bigger than our planet. Are we sure photons are particles ???
lambda = c/f = 300000/1 = 300000 km
- 35
1
vote
3
answers
148
views
Lorentz ether theory (LET) vs special relativity
According to wiki LET page
“[Mansouri–Sexl] implies that a one-way speed of light experiment could in principle distinguish between LET and SR… In the absence of any way to experimentally distinguish ...
- 93
3
votes
0
answers
104
views
Rigorous Justification for "Only Available Tensor"
In many instances, for example in particle physics, some argument of the following form is given: This rank 2 tensor we have here is a function of some vector (say $p^\mu$), so it must be some linear ...
- 497
-3
votes
1
answer
88
views
Inertial Frames, Relativity, Equivalence Principle and the Twin Paradox [duplicate]
I am very unsatisfied with how people resolve the twin paradox. As a little background, here is what the Wikipedia article about the paradox states...
In physics, the twin paradox is a thought ...
- 155
-6
votes
0
answers
73
views
Physics special theory of relativity [duplicate]
Read the question till end scenario may be seem to be same but at last there is different questions.
Scenario:
Inside the moving train: You're sitting in a train that is moving with respect to a ...
0
votes
0
answers
50
views
The twin paradox in a periodic metric [duplicate]
I'll keep it simple as this is a very simple twist on the famous twin paradox. The twin paradox is resolved by the fact that for the clocks to actually meet up again one of them has necessarily ...
- 1,897
-2
votes
1
answer
81
views
Limit of relative speed [duplicate]
Let us suppose that two rockets travel in opposite directions from the earth. The speed of each is more than half the speed of light. My question is whether the two rockets will travel at more than ...
- 129
1
vote
2
answers
147
views
Speed of Light vs Speed of Massless Particles
As I understand it, there are a few different massless particles. Is there anything that differentiates these from each other besides frequency/wavelength?
My definition of speed would be the time it ...
- 11
0
votes
1
answer
34
views
Calculating Pion momenta for probing different structures using de Broglie wavelength
for the following question:
Consider a pion ($π^\pm$) scattering on a target. What pion momenta are needed to observe structures of the size of an atom
($10^{-10}$ m), an atomic nucleus ($10^{−14}$ m)...
0
votes
2
answers
119
views
Is there a common mechanism that gives rise to spatial and time dilation in both Einstein's STR and GTR?
In both General and Special Relativity a body experiences both time and spatial dilation. For example, as a particle approaches C it experiences dilations in time and space. For a particle ...
- 21
-1
votes
1
answer
51
views
Time dilation effect for astronauts travelling to Alpha Centauri Sol in a spaceship at $0.87c$ the speed of light? [duplicate]
Does this mean also that if we want to sent astronauts to Alpha Centauri solar system, 4lys away with the spaceship accelerating to $0.87c$ speed of light (i.e. Lorentz factor γ=2), then the spaceship ...
- 4,376
-6
votes
3
answers
182
views
Will a spaceship moving at $0.87c$ the speed of light, age twice less? [closed]
Strangely enough, the physics community seems to me having opposing views on this, namely many say that constant speed SR time dilation effects in the rest frame of an relativistically moving massive ...
- 4,376
0
votes
4
answers
123
views
Lorentz transformation from the Minkowski metric
Is it possible to derive the matrix:
$$\Lambda=\begin{pmatrix}
\gamma & -\beta\gamma \\
-\beta\gamma & \gamma
\end{pmatrix}$$
From the condition:
$$\Lambda g\Lambda^T=g \ \ \ \ g=\begin{...
- 371
30
votes
2
answers
2k
views
Temperature and time dilation
Say you had some liquid radioactive isotope with a half-life equal to X. If it was cold, the molecules would move slowly, and thus there would be virtually no time dilation involved, resulting in the ...
- 403
0
votes
1
answer
85
views
Simplification of the Differential Cross Section in Peskin and Schroeder
I am reading p. 107 in Peskin and Schroeder's QFT, and I am stucked on one of the steps they took while calculation $2\rightarrow 2$ cross section. For $A+B\rightarrow 1+2$ differential cross section ...
- 3
1
vote
0
answers
67
views
Please help understanding Marinov's generator
I've been working through an interesting puzzle in classical electromagnetism with a fellow researcher, and we've hit a wall. We're hoping the physics community might be able to shed some light on ...
- 43
-3
votes
2
answers
102
views
How to prove that events A and B are the same as C and D (A=C, B=D) in two different systems if their spacetime intervals are equal? [closed]
Consider two spacetime intervals that are equal in two different intertial systems 1 and 2: $$s_1^2=s_2^2$$
Let events A and B happen in system 1 and have coordinates: $$A(T_a,X_a,Y_a,Z_a)$$ $$B(T_b,...
- 431
4
votes
1
answer
247
views
Is there an simple derivation of the solution to the Submarine Paradox in terms of Special Relativity?
In 1989 James Supplee formulated the Relativistic Submarine Paradox.
A quick synopsis of the submarine paradox:
Consider a submarine that is neutrally buoyant when stationary relative to the water.
...
- 10.1k
0
votes
4
answers
140
views
One-way speed of light and the luminiferous aether
The "luminiferous aether" hypothesis is famously falsified by the Michelson-Morley experiment. It is explained that if there is an aether and we move through it, then there will be an "...
- 109
1
vote
2
answers
153
views
A 12th-grade physics question about inductors
I'm a 12th-grade student learning about inductors, and there's a question that’s been bothering me. I’m not an expert, which is why I’m asking here. If anyone knows the answer, please explain it as if ...
- 11
1
vote
0
answers
52
views
Which is the Lorentz group representation the Majorana Rarita-Schwinger spinor transforms like?
In the textbooks --- for instance "Freedman & van Proeyen" -- it is said that the Majorana Rarita Schwinger spinor is a combination of a Majorana spinor and a vector. In order to the ...
- 10.2k
-1
votes
1
answer
49
views
Understanding field lines of uniformly moving charging
Here you can simulate a moving point charge's field lines. I cannot conceptualise why uniformly moving charges do not create breaks in the field lines.
As I see it, the information of a charge having ...
- 167
0
votes
5
answers
523
views
Is the Lorentz-contracted length of an object its true length in the stationary frame?
Let's consider an iron rod, weighing $55.8\,\text{g}$ ($6\times 10^{23}\,\text{atoms}$) and having a cross section of $1 \,\text{cm}^2$. Its volume (one mole) is $7.1 \,\text{cm}^3$. Its proper length ...
- 129
1
vote
1
answer
59
views
Why can coefficient $a$ between spacetime intervals depend on absolute relative velocity between the systems?
I read Landau & Lifshitz' Classical Theory of Fields book (page 14-15) (see pic below) and I was confused when I saw in proof that coefficient $a$ between spacetime intervals $(ds)^2$ and $(ds')^2$...
- 431
4
votes
0
answers
217
views
Understanding instantaneous rest frames in general relativity
In special relativity, to derive formulas for proper time and proper distance, one uses the concept of instantaneous rest frames.
In order to calculate proper time of a massive object moving in the ...
- 711
0
votes
1
answer
99
views
Does speed affect gravitational force according to special relativity? [duplicate]
According to the special relativity, when the speed of an object increases, its mass also increases. Does it mean that objects moving at speeds close to the speed of light exert higher gravitational ...
- 744
3
votes
2
answers
260
views
An object with mass cannot travel with the speed of light in vacuum but what if lights speed in a medium is below the object's speed? [duplicate]
I read in my Physics textbook that when light falls perpendicularly on an optically denser medium it doesn't change its path rather it's speed slows down. If after multiple refractions the speed of ...
4
votes
1
answer
140
views
Why does $E=mc^2$ allow for the creation of particle-antiparticle pairs?
This is a line from Chapter 2 of Peskin:
"We have no right to assume that any relativistic process can explained in terms of a single particle, since the Einstein relation $E = mc^2$ allows for ...
- 43
0
votes
1
answer
59
views
Lorentz transformation on field theory using coordinate expressions not representations
This is probably a stupid question but, I want to show that a Lagrangian written in field theory is Lorentz invariant WITHOUT using the Lorentz transformation representation / generators. I know we ...
- 1
0
votes
0
answers
44
views
A good reference for irreducible decomposition like $(2,1)\otimes (1,2)=(1,1)_A \oplus (3,1)_S$?
M. Srednicki says in the book "Quantum Field Theory" on page 211 that:
I would really appreciate if someone could introduce me a good reference for understanding the irreducible ...
-2
votes
1
answer
93
views
Would light travelling through curved, expanding space, experience a Doppler shift due to the expansion of the space?
Assume the curvature is spherical.
Below is a link to a related question, but that became bogged down on the issue as to whether a sound signal travelling around the surface of an expanding balloon, a ...
- 121
-6
votes
3
answers
134
views
What exactly is the role of the Lorentzian metric within spacetime? [closed]
I learned that twodimensional spacetime diagrams and fourdimensional spacetime manifolds are provided with Lorentzian (pseudo-Riemannian) metric. However, regarding a spacetime diagram with a light ...
- 3,151
0
votes
0
answers
38
views
Lectures Notes on Maxwell-Jüttner distribution function
I have been looking online for good notes on the application of relativity to statistical mechanics, in particular about the Maxwell-Jüttner distribution function. Does anyone have some links to ...
0
votes
0
answers
28
views
How should loss of crystal symmetry due to Lorentz contraction be interpreted in the stationary frame?
A crystal with cubic symmetry moving at a relativistic speed would appear to have lost that symmetry as viewed from the stationary frame due to Lorentz contraction of its axis in the direction of ...
- 129
0
votes
1
answer
73
views
Apparent Woodhouse Galilean Maxwell Paradox
I don't understand this Maxwell paradox in Woodhouse's relativity. The first equation implies that there are fields working on the moving charge, but the last equation implies that the magnetic field ...
- 131
11
votes
2
answers
288
views
Does Lorentz transformation affect mass density, pressure or temperature of a physical object?
A cylinder filled with gas and moving along its axis would be Lorentz contracted, diminishing its volume. Viewed from stationary frame, would the pressure of the gas be higher than in the co-moving ...
- 129
-4
votes
1
answer
219
views
The relativistic Doppler effect is a function of relative velocity. But does the velocity also have to be non-zero relative to the travelling signal?
The classical Doppler effect is a function of that component of the velocities of source and receiver in the direction of the travelling signal. The relativistic Doppler effect is a function of the ...
- 121
0
votes
0
answers
40
views
Does the Lagrangians in different coordinate systems differ by a total derivative when converted to the same coordinate in special relativity?
According to this post, it seems like we should use the $$\mathbb{L}~=~L \mathrm{d}t~=~ L \dot{t}\mathrm{d}\lambda \tag1$$ rather than $$L(v'^2) = L(v^2)+ \frac{df}{dt}\tag2$$ when working with ...
- 413
8
votes
3
answers
675
views
Cherenkov radiation in the frame of a moving observer
Imagine a medium in which an electron is moving at speeds faster than the speed of light in the medium. Within the same medium an observer moves at the same speed with the electron. Will the observer ...
- 1,415
1
vote
1
answer
75
views
Potential Textbook Typo in Calculation of Lorentz Transformation
In the 3rd edition of Goldstein's Classical Mechanics (pp. 283-284), the authors consider three inertial frames $S_{1}$, $S_{2}$, and $S_{3}$ where the Lorentz transformation from $S_{1}$ to $S_{2}$ ...
- 335
0
votes
1
answer
39
views
Can a reverse-parabolic screen in the double-slit experiment test local vs. nonlocal interference formation?
Suppose that in a double-slit experiment, the slits open just in time for a photon to pass through, and a reverse-parabolic screen is used, with edges positioned much farther from the slits than the ...
- 686
-1
votes
1
answer
105
views
Is relativistic action too restrictive?
When I was studying special relativity, I've learned that the relativistic action for a free particle is defined as
$$
S = \lambda \int_{\tau_0}^{\tau_1} d\tau
$$
Where $\lambda$ is a constant that is ...
- 3,335
2
votes
0
answers
44
views
Lorentz invariance in statistical physics
Given a function $f=f(p^\mu)$ with $p^\mu$ the four-momentum I can integrate it over the full phase-space with $\int\mathrm{d}^{d+1}p\ f(p^\mu)$. This, however, is usually not very useful, since the ...
-6
votes
2
answers
114
views
Are high-energy neutrinos subject of relativistic time dilation like muons are?
Synchrotron experiments and cosmic-rays hitting our atmosphere have proved many times that high-energy massive muons moving with speeds close to the speed of light are subject to relativistic length ...
- 4,376