Questions tagged [non-locality]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
2 votes
1 answer
67 views

Is there something that violates "time locality"?

The way I understand locality is that for an object to influence another object away from it, it has to do so through the space that separates them. It can shoot out an EM wave to the other object, ...
user avatar
0 votes
0 answers
22 views

Are only local hidden variables at odds with special relativity?

So hidden variables in quantum mechanics are at odds with special relativity. I can understand this to be the case with local hidden variables, but does this also hold for non-local ones? Often one ...
user avatar
0 votes
1 answer
63 views

Local nature of physical laws

All the laws in physics are local in nature and that's why their formulation follows differential equations. My doubt is whether the locality is a proven theorem or it is a postulate?
user avatar
  • 11
3 votes
2 answers
131 views

Effective action as a generating functional and its derivative expansion

On page 381 of Peskin and Schroeder, equation (11.90) reads $$ \frac{\delta^2 \Gamma}{\delta \phi_{cl}(x)\delta \phi_{cl}(y)} = iD^{-1}(x,y).\tag{11.90}$$ I am having a bit of trouble interpreting ...
user avatar
  • 777
2 votes
2 answers
103 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 ...
user avatar
  • 1,420
0 votes
0 answers
49 views

Feynman rules for non-local theory

For model with interaction: \begin{equation} H_{int} = \int f(\boldsymbol{x}_{1},\boldsymbol{x}_{2},\boldsymbol{x}_{3})\hat{\varphi}_{S}(\boldsymbol{x}_{1})\hat{\varphi}_{S}(\boldsymbol{x}_{2})\...
user avatar
0 votes
0 answers
46 views

Lagrangian depending on running integral

In the theory of calculus of variations, the Lagrangian generally depends on the unknown function and its first derivative. This assumption leads to the Euler-Lagrange equations. However, I found that ...
user avatar
0 votes
0 answers
40 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 ...
user avatar
1 vote
1 answer
64 views

Could Planck scale wormholes be a solution for non-locality?

When two entangled particles are separated, an observation made on one particle seems to be able to act at a distance to determine the state of the other particle. Is it possible, or has anyone in ...
user avatar
3 votes
1 answer
153 views

Non-local connection Between $D$ and $E$ (Kramers-Kronig relations)

I'm trying to solve next exercise from Jackson's Electrodynamics, Chapter 7, page 348, 3th edition: Consider the non-local (in time) connection between $D$ and $E$, $$\vec{D}(\vec{x},t)=\epsilon_0 \...
user avatar
  • 33
2 votes
1 answer
121 views

Is nonlocality consistent with scale invariance?

For sure I'm excluding gravity at first step, the question is that if nonlocality is compatible with scale invariance. At the classical and quantum levels for field theory in Minkowski spacetime. Then ...
user avatar
2 votes
2 answers
209 views

Why is Pilot Wave Theory nonlocal?

I have read that the Pilot Wave Theory is nonlocal and can therefore be excluded. Why is the PW Theory nonlocal? Isn't QM also nonlocal, as we can see it from entanglement? I already googled the ...
user avatar
  • 319
2 votes
4 answers
202 views

Computer analogy to non-locality in quantum mechanics

It is not uncommon to say that the non-locality of quantum mechanics is equivalent to the following computer analogy: if you are trying to model an entangled two spin system, then even if the spins ...
user avatar
0 votes
0 answers
51 views

Nonlocality in the Many Worlds question

David Wallace and Lev Vaidman have said the MWI is nonlocal. "The overall story about locality in Everettian quantum physics, then, is this: the dynamics of the theory are local: there is no ...
user avatar
  • 545
4 votes
4 answers
220 views

What is wrong with violation of locality (EPR paradox)?

When studying the EPR paradox, at some point we must resign ourselves that Reality and Locality can not be both true in the current theory of quantum mechanics. A lot has been said in Physics.SE about ...
user avatar
0 votes
3 answers
82 views

Does quantum entanglement necessitate that two particles communicate their state with one another?

I often hear it said that quantum particles, like an electron-positron pair or two entangled photons, which are entangled with one another communicate or transfer information about their state ...
user avatar
  • 121
1 vote
1 answer
138 views

Is QFT "more" non-local than QM, at least mathematically?

Could physics still be local? Here's what I mean: The Schrodinger/Dirac equations allow for quantum entanglement, right? So in that sense they are non-local physically. But they are mathematically ...
user avatar
  • 1,468
2 votes
0 answers
79 views

Non-locality and Twistor functions

Is there a nice intuitive way to visualize the concept of non-locality associated to twistor functions? And how is it related to the type of non-locality we encounter in Quantum Mechanics?
user avatar
  • 867
1 vote
1 answer
71 views

Local vs Nonlocal electrodynamics

I am having a hard time to understand the difference between local and nonlocal electrodynamics. Does the former refer to the case when the charge (i.e electron) can be localized and the latter refer ...
user avatar
0 votes
0 answers
39 views

Has there been experimental evidence that entangled state collapses simultaneously?

If we observe the observable of one particle among two particles which are entangled each other and separated far away, we can determine the value of the other particle’s same observable from the ...
user avatar
  • 33
2 votes
1 answer
127 views

Where does the negative cosine relation for quantum mechanical CHSH correlations come from?

I have been lately looking into Bell's inequality. I have noticed a recurring graph that depicts the correlation of two spins when measured at different angles, for the quantum and the classical case: ...
user avatar
  • 127
0 votes
1 answer
75 views

Many worlds is nonlocal too after all according to some physicists?

Not a physicist but I have understood that MWI is unique in that it preserves local dynamics. There is a wavefunction - not in spacetime but in some more abstract space. But the worlds with spacetime ...
user avatar
  • 545
1 vote
0 answers
72 views

Renormalization of non-local product of operators

In Unraveling hadron structure with generalized parton distributions by Belitsky and Radyushkin, appendix G, eq. (G.47) it is said that for renormalization of an on-local product of operators such as ...
user avatar
  • 1,174
2 votes
0 answers
50 views

Are violations of realism the same thing as contextuality?

I am basically looking for a counter-example where we'd get contextuality but not violations of realism (and vice-versa). If no such counter-examples exist, then it seems to me that they're really one ...
user avatar
  • 1,185
0 votes
2 answers
89 views

How to rule out all forms of "realism"?

Thus, we see that local causality condition (1) is mathematically equivalent to the assumption of joint probabilities, $p(A_1,A_2,B_1,B_2)$. The latter is a form of realism: complementary observables ...
user avatar
  • 45
0 votes
1 answer
39 views

Does non-local interepretations of quantum mechanics imply FTL communication? [closed]

For example the pilot wave theory... And if this is the case then does FTL commuincation imply time travel (i.e: information going back in time).
user avatar
2 votes
0 answers
25 views

Is it possible to use Quantum Monte Carlo for non local interactions?

I just have a brief question about QMC being applied to calculating expectation values. If I were to calculate the expectation value of an operator, like the energy via a Quantum Mote Carlo ...
user avatar
1 vote
1 answer
108 views

Non-locality of pre-Klein-Gordon equation

In Relativistic Quantum Mechanics, Bjorken and Drell state that expanding the square root in the equation $$-\hbar^2\frac{\partial^2\psi}{\partial t^2}=\sqrt{-\hbar^2c^2\boldsymbol{\nabla}^2+m^2c^4}\...
user avatar
1 vote
1 answer
66 views

If quantum entanglement causes the violations of Bell's inequality why don't we see perfect correlation?

From wikipedia: For example, if a pair of entangled particles is generated such that their total spin is known to be zero, and one particle is found to have clockwise spin on a first axis, then the ...
user avatar
  • 794
0 votes
0 answers
111 views

How can quantum nonlocality be understood in the path integral formalism?

I have always had my difficulties (being bored, impatient) with the theoretical considerations around quantum nonlocality, especially Bell's inequalities. What makes it cumbersome for me is that these ...
user avatar
  • 6,875
2 votes
2 answers
135 views

How to take 'non-local' functional derivatives?

I am currently in the process of getting into linear response theory in general, and I have often met functional derivatives of the type $$\frac{\partial J[f(x)]}{\partial f(y)} = \chi(x,y).$$ I've ...
user avatar
0 votes
1 answer
54 views

Quantum Erasure - what causes the phase difference in the two interference patterns observable at Do?

In the Delayed Quantum Erasure experiment, I understand that the interference patterns that you would see at Do is associated to the entangled photons that eventually arrive at D1 or D2 (which-way ...
user avatar
1 vote
1 answer
64 views

How does quantum contextuality relate to realism?

According to Spekkens contextuality can be defined as follows: Suppose A, B and C are Hermitian operators such that A and B commute, A and C commute, but B and C do not commute. Then the assumption ...
user avatar
  • 1,185
4 votes
1 answer
97 views

Easiest way to see that superposition is necessary?

I have been discussing QM with a friend and wanted to explain why holding on to realism means we must accept non-locality. Essentially I got hung up on explaining Bell's Theorem in simple words. I ...
user avatar
  • 689
1 vote
2 answers
143 views

How does relaxing counterfactual definiteness allows for CHSH inequality violation?

Scenario, I want to play a game with a group of students as a teacher, I ask two teachers to help. The students are from the central classroom, going to room A and room B where the teachers there asks ...
user avatar
6 votes
0 answers
90 views

A Venn diagram for: (non-)locality, (non-)realism, (non-)contextuality, (non-)signalling, (dis-)entanglement

I recently asked a (yet-unanswered) question about the relationship between state-dependence and violations of realism. The more I read on the subject, the more I find myself digging deeper in a ...
user avatar
  • 1,185
5 votes
2 answers
223 views

How can a disentangled state be contextual?

I (re-)learned about Bell tests from the ground up based on this very intuitive lecture by Spekkens. In a nutshell, realism is violated whenever measurement statistics cannot be reproduced by ...
user avatar
  • 1,185
-4 votes
1 answer
80 views

Question on hidden variable theory of QM [closed]

My understanding from careful study of Bells theorem is that there may be a deep subtlety that is not ruled out, but is probably very minimally studied in the literature. However the literature is ...
user avatar
  • 450
2 votes
1 answer
143 views

Is Bell nonlocality compatible with, or even predicted by, quantum field theory?

Bell's theorem, together with experiments confirming the ordinary quantum mechanical distant correlation predictions which violate its conclusion for local theories, show that any entirely local ...
user avatar
2 votes
1 answer
85 views

Are following statements valid for quantum gravity?

In the concluding section of this post user Chiral Anomaly states following: On the other hand, since any stable marriage of quantum theory and gravity (in the sense of general relativity, not just ...
user avatar
  • 2,815
1 vote
1 answer
122 views

Non-analytic functions and non-local Lagrangians

Infinite sums of increasingly higher-order derivatives, when present in Lagrangians, are typically taken as a sign of nonlocality. This is supposed to rule out fractional, negative and exotic (for ...
user avatar
  • 461
4 votes
0 answers
131 views

What does it mean for an extended operator to possess "local excitations"?

In the context of defect conformal field theory, we consider in operator product expansions "local excitations" of the defect (see e.g. text between eq. $(1.1)$ and $(1.2)$ in the paper ...
user avatar
  • 1,493
1 vote
0 answers
34 views

What is an "optimal ensemble" used to demonstrate quantum steering?

I am reading Wiseman et al. (2007) and Jones et al. (2007) papers on quantum steering. They relied on the existence of "optimal ensembles" for a Local Hidden State theory. They make use of ...
user avatar
3 votes
1 answer
193 views

Blocking quantum effects

A Faraday cage blocks electromagnetic fields, provided they are not intense enough to change the state to something non-conductive (e.g. slicing it in two with a laser). Is there any analogous system ...
user avatar
  • 141
0 votes
2 answers
173 views

Why quantum mechanics doesn’t break locality in entanglement but hidden variables theories will?

What makes it so that quantum mechanics doesn’t break locality in entanglement yet hidden variable theories will? In Bell‘s inequality said that hidden variables theories need to break locality in ...
user avatar
0 votes
1 answer
41 views

Light in action-at-a-distance formulation of Electromagnetism

If it is possible to use Jefimenko's equations to formulate Electromagnetism as a non-instantaneous action-at-a-distance theory, what would electromagnetic radiation be in such a theory? Would it be a ...
user avatar
1 vote
0 answers
53 views

Concrete Example of Quantum Entanglement, Quantum Steering and Bell Nonlocality

I was reading the wikipedia page for quantum steering. The following is the mathematical way they have described the three notions: Is there any concrete example of these three concepts? Like, any ...
user avatar
4 votes
2 answers
115 views

What is locality?

In QFT and statistical mechanics, one is usually interested in studying integrals of the form: $$Z(\phi) =\int d\mu_{C}(\phi')e^{-V(\phi+\phi')}$$ where $\mu_{C}$ is Gaussian measure with mean zero ...
user avatar
  • 487
6 votes
1 answer
237 views

Functional Analytic Square Root of Hamiltonian Alternative to Dirac

I was thinking about the history of the Dirac equation and asked myself, what happens if one simply considers the Schrödinger equation $$i\hbar\frac{\partial\phi}{\partial t}=\sqrt{-c^2\hbar^2\Delta+m^...
user avatar
  • 3,394
6 votes
1 answer
350 views

Argyres-Douglas CFT

Adding of mass in supersymmetric gauge theories will affect structure of moduli space by creating new singular point (picture and some statements from Matteo Bertolini: Lectures on Supersymmetry): ...
user avatar
  • 5,341