Questions tagged [locality]
The locality tag has no usage guidance.
260
questions
0
votes
0
answers
115
views
How do Lieb-Robinson Bounds talk about locality without the position operator?
So we know when one goes from QM to QFT Lieb Robinson bounds become micro causality. But micro causality is a statement on the commutators assuming they are space-like, time-like or light-like. ...
- 1,389
1
vote
0
answers
41
views
Locality in Bell Experiments
I have a question about experiments that show a violation of Bell's inequalities. It's said that these experiments disprove local realism. However, immediately before the final measurement of the 2 ...
- 201
5
votes
1
answer
125
views
Conserved charge at null infinity associated with Large gauge transformation
I am reading Strominger's lecture notes "Lectures on the infrared structure of gravity and gauge theory" (https://arxiv.org/abs/1703.05448). At some point, following (I guess) the authors of ...
- 3,992
9
votes
2
answers
372
views
How are we able to use quantum field theory to study systems?
I've been trying to understand the concept of locality in QFT, and I was reading this paper by Edward Witten, where he explains (on pg 13) that the state space cannot be factored into a tensor product ...
- 5,488
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
502
views
Locality of interactions and their high energy behavior
In a classic Georgi review of EFT, I have read the following quote
The result of eliminating heavy particles is inevitably a
nonrenormalizable theory, in which the nontrivial effects of the heavy
...
- 1,742
3
votes
2
answers
692
views
Why does one work with the Lagrangian density in field theory?
Why is it necessary to introduce the Lagrangian density (integral of the Lagrangian over volume) when describing the dynamics of fields? Is there a specific reason for that or just for convenience?
- 363
4
votes
1
answer
295
views
On the Bell's Theorem / Bell-type Inequalities and the Kochen-Specker Theorem
It appears to me that the Kochen-Specker theorem, if not Gleason’s theorem already, seals the fate of realism / value definiteness (with possibly the additional assumption of non-contextuality, ...
- 173
0
votes
0
answers
50
views
Interpretations for Interaction-free measurements
So I read several papers on IFM by Vaidman, Dicke, and many others, In all of them I think the Pilot wave theory is able to adequately justify the observations, but then I came across several papers ...
3
votes
0
answers
94
views
Are all physically realistic Hamiltonians local?
My understanding of modern physics is that physicists think that, fundamentally, physical laws are local. For system A to interact with system B, they either need to be very close to each other or ...
- 1,327
7
votes
1
answer
608
views
How did the local hidden variable theory resolve the EPR paradox?
I'm trying to understand the motivation for local hidden variable theory. The EPR paradox considers the following thought experiment, where we can express a state $|\psi \rangle \in H_{Alice} \otimes ...
- 204
4
votes
5
answers
114
views
Is Electrostatics Local?
We can solve uniquely for the electrostatic potential $\phi(x)$ of some given charge distribution if we set the boundary condition that $$\lim_{|x|\to\infty}\phi(x) = 0$$ (or whatever boundary ...
- 1,647
2
votes
0
answers
193
views
Conformal Field Theory and Vertex Operator Algebra
I am trying to understand CFT from the viewpoint of both math(in particular using VOA) and physics. Now, in Math, we use the VOA to make sense of fields corresponding to certain states. We define for ...
- 83
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