All Questions
Tagged with locality special-relativity
33
questions
0
votes
0
answers
62
views
Can you model relativistic interactions without locality?
Assume $c=1$
I've been doing relativity by myself so I may be making some assumptions here that I would not have if my learning had been more extensive.
One such assumption is that you can model the ...
- 312
0
votes
0
answers
35
views
Lorentz invariance (LI) of time ordering operation
At Srednicki after eq. (4.10), we have a discussion about that the time ordering operation. Have to be frame inv. I.e it has to be LI.
He wrote that for timelike separation we don't have to worry ...
1
vote
1
answer
191
views
$SO(3,1)$ is locally $SU(2)\times SU(2)$, what does *locally* mean here?
I am learning Lie group and Lie algebra. I saw in a YouTube video "Supersymmetry lecture 02" from OpenCourseWare (OCW) at University of Cambridge at 11:17 that
$SO(3,1)$ is locally $SU(2) \...
- 53
2
votes
1
answer
89
views
How to interpret Poisson bracket of fields in terms of causality?
In quantum field theory, the fact that space-like separated observables commute, i.e. $[\hat {\phi (x)}, \hat{\phi(y)}]=0$, is taken as the test for causality. The equivalent statement for classical ...
- 519
1
vote
2
answers
162
views
How is the non-locality of a theory apparent from its mathematical form?
I am reading Relativistic Quantum Mechanics by Bjorken and Drell and on page 5 they present the following attempt at a relativistic Hamiltonian for a free particle
\begin{equation}
i\hbar\frac{\...
- 229
3
votes
1
answer
754
views
Proof that conservation of momentum is Lorentz invariant
In classical mechanics, if
$$\frac{\mathrm d}{\mathrm d t}\sum_i m_i\vec{v_i}=0$$is true for one frame of reference, then it is easy to prove that this is true for all frames (since different frames ...
- 1,801
1
vote
0
answers
91
views
Is causality a consequence or a constraint in physics?
I wonder if causality is a constraint that we must add to physical models (if needed), or is it a consequence of Lorentz invariance and locality (or something else). In other words, which properties ...
- 595
0
votes
2
answers
57
views
Must all field theories depend on the spatial derivate of the fields?
For instance, if I have encountered
\begin{equation}
\label{eqq2}
\frac{\partial \mathcal{L}}{\partial (\partial_i \phi)} = 0
\end{equation}
This tells us that $\mathcal{L}$ cannot depend on $\...
- 1,031
4
votes
1
answer
457
views
How does string theory get around the argument in Weinberg's QFT?
In Weinberg's The Quantum Theory of Fields Vol. 1, an argument is presented that the three postulates of
Lorentz invariance
quantum mechanics
cluster decomposition principle
leads to quantum field ...
- 857
2
votes
2
answers
193
views
Global conservation + Lorentz invariance = local conservation?
On the page 83 of "Quantum Field Theory Lectures of Sidney Coleman", Coleman showed an interesting example:
It seems that global conservation law and local conservation law can be related. ...
- 192
2
votes
1
answer
161
views
Thought experiment in relativistic quantum mechanics?
Background
Consider the following thought experiment in the setting of relativistic quantum mechanics (not QFT). I have a particle in superposition of the position basis:
$$ H | \psi \rangle = E | \...
- 1,389
0
votes
2
answers
97
views
Why can't light travel three days into the future then transmit that information back to us prior to us arriving at that position? [closed]
Example: If a football game between the Pittsburgh Steelers @ Tennessee Titans will happen in 3 days Sunday 10/25/2020 at 1pm, why can't light leave today 10/22/2020 and go to where the Earth will be ...
2
votes
2
answers
292
views
How Maxwell theory of electromagnetism solved action at a distance problem?
According to wikipedia Maxwell's equations were an essential inspiration for Einstein's development of special relativity. Possibly the most important aspect was their denial of instantaneous action ...
- 21
1
vote
0
answers
152
views
Relativity and Bell's inequalities
I am reading a collection of interviews taken with prominent physicists as in an aftermath of famous Alain Aspect experiment. Between them John Bell states that if local realism has to go, he would be ...
- 39
2
votes
1
answer
124
views
Particle here at a given time, in another galaxy a second later... Really?
I read "The Quantum Universe (Cox & Forshaw)" that a particle can be measured at a given position at a given time, and in another galaxy one second later. The probability of such event may be ...
- 347