Questions tagged [non-locality]

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111 views

Is there a relation between the factorisation of the joint conditional probability distribution and Bell inequality?

I'm approaching the study of Bell's inequalities and I understood the reasoning under the Bell theorem (pdf : https://cds.cern.ch/record/111654/files/vol1p195-200_001.pdf) and how the postulate of ...
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Non-local field theory (of Jaffe type) vs strings

As it is well known expectation values of fields are distributions. One usually works with tempered distributions or even with Jaffe fields (https://doi.org/10.1103/PhysRev.158.1454), all defining ...
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In a Bell scenario, why can correlations be nonlocal only if there are at least two measurement settings to choose from?

In (Brunner et al. 2013), the authors mention (end of pag. 6) that a set of correlations $p(ab|xy)$ can be nonlocal only if $\Delta\ge2$ and $m\ge2$, where $\Delta$ is the number of measurement ...
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341 views

Local determinism vs. Local realism vs. Local causality

I found the following definitions for the three different terms. Do you find these definitions exhaustive, or can you suggest more precise formulations? Quoting the wikipedia page on Local realism: ...
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Can local hidden variables models be ruled out without invoking expectation values?

Bell's inequalities, in their standard form, are a statement about the limitations faced by a probability distribution that can be written as $$p(a,b|x,y)=\sum_\lambda p(\lambda) p(a,b|x,y,\lambda)=\...
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139 views

Can non-locality be considered an instantaneous propagation of the field?

I've read the article Quantum Entanglement, which is a summary of the basics of non-locality, as well a claim for the first "real" proof of its existence. I also have some background from self-...
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Decomposition of rank-2 field and local interactions

Any rank-2 tensor can be decomposed in the following way $$ \phi_{\mu\nu} =\phi_{\mu\nu}^{TT} + \partial_{(\mu}\xi_{\nu)} +\frac{1}{4}T_{\mu\nu}s+\frac{1}{4}L_{\mu\nu}(w-3s) $$ where $\phi_{\mu\nu}^{...
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Does photon absorption annihilate the associated EM wave instantly?

My Understanding A single photon has an associated electromagnetic wave. The wave is spread out in space, but the photon is considered a point particle. If the photon is absorbed, the entire wave ...
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133 views

How to deduce quantum non-locality from indeterminism?

In the paper ''Quantum non-locality as an axiom'' (Popescu, S. & Rohrlich, D. Found Phys (1994) 24: 379. https://doi.org/10.1007/BF02058098), it is stated that the conventional formalism of ...
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318 views

Why can't Faddeev-Popov ghosts be replaced with bosons?

Faddeev-Popov ghosts are introduced in the quantization of Yang-Mills theory to absorb the Faddeev-Popov determinant into the action, $$\det \Delta_{\text{FP}} = \int \mathcal{D} \bar{c} \mathcal{D} c ...
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606 views

Local and Non-Local Potentials

Can anybody explain the difference and concepts between local and non-local potentials in light of quantum mechanics?
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52 views

Finding the cost functional of a car-following model [closed]

I have a car-following model with delay $\ddot{x}_n(t)=\lambda [\dot{x}_{n-1}(t-T)-\dot{x}_{n}(t-T)]$, where $\ddot{x}$ is the acceletation, $\dot{x}_{n-1}-\dot{x}_{n}$ is the relative velocity, $\...
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104 views

EPR-Bohm paradox and Robertson uncertainty relation [closed]

Consider Bohm's version of the EPR paradox, where spin-1/2 are used. The bipartite system is in the state $$ \vert \Psi\rangle = \dfrac{1}{\sqrt{2}} \left( \vert \uparrow_x \rangle_A \vert \...
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Intuition behind non-local stress tensor

Starting from the following Reisz Fractional Integro-differential formula (see for example https://www.amazon.com/Fractional-Integrals-Derivatives-Theory-Applications/dp/2881248640, chapter 25) $$ I^{...
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Is there any basis in stating there are different levels of 'locality' or 'reality', within physics or physical theories?

EPR’s reality criterion and quantum realism has this paragraph (the paper has 0 citations, and I'm personally happy to call this metaphysics, but still!): A popular interpretation of Bell’s theorem ...
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96 views

Are contextual theories non-local and vice-versa?

I am wondering if every contextual theory that reproduces QM is NON-local and reciprocally. Otherwise, when is contextuality equivalent to non-locality? And moreover, how much nonlocality is encoded ...
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What's a comprehensive review of the implications of Bell-nonlocality on our notion of reality / Weltanschauung?

I am looking for a (preferably peer-reviewed) article that summarizes: the historic debates surrounding Bell-nonlocality, how nonlocality can/not be reconciled with our notation of reality, and ...
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1answer
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What is space according to quantum mechanics?

We have a pretty good idea what space is in general relativity, yet the strange fact of non-locality in quantum mechanics tells a different story. Interestingly enough this non-locality doesn't seem ...
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3answers
189 views

Problem with argument for the existence of the electric field

In the Extended Third Edition of "Physics for Engineers and Scientists" by Ohanian and Markert (pp. 722-723), it is written: According to the naive interpretation of Coulomb’s Law, the electric ...
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1answer
154 views

How to build an Elitzur–Vaidman bomb tester?

I would like to personally recreate the Elitzur–Vaidman bomb tester experiment. Is that generally possible with maybe only a few thousand dollars to invest or maybe even for a few hundred? Any ...
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Locality in QFT vs “non-local” in QM

In quantum mechanics (QM), teacher always emphasizes on the "weird" parts, like EPR paradox, Bell inequality and so on. The Bell inequality tells us that QM is either nonlocal or non-realistic or both....
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1answer
219 views

How can quantum entanglement not be non-local?

I know this kind of question has been brought up many times.I have read many posts here regarding this but I still have a problem with a certain aspect of it so please bear with me. Lets consider the ...
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93 views

“Logical Conclusions” arising from hypothetical wormholes

EDIT In eternal (time independent) Schwarzschild black hole contains a wormhole called an Einstein-Rosen bridge. But since no real black hole is eternal, real black holes do not contain any ...
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1answer
339 views

What exactly are the high energy problems between general relativity and quantum field theory? [duplicate]

I know there are many questions on physics stack exchange devoted to the question of quantum gravity and reconciling GR and QFT, but don't mark this as a duplicate because my question is a bit more ...
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358 views

Is there non-locality in the AdS/CFT?

Many String theorists are trying to restore bulk locality in the AdS/CFT. So does that mean the CFT, the boundary, is non-local? Does matter travel faster than light on the CFT?
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366 views

Non-local field redefinition and $S$-matrix

It is known that for local field redefinitions for which the LSZ formula is valid: $$\langle 0|\phi(x)|p\rangle \neq 0$$ field redefinitions don't change the S-matrix. (See QMechanic's answer to ...
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384 views

How can non-locality of entanglement be explained only in terms of correlation?

I'd like to ask a very specific question about the entanglement nonlocality. I know that it is not possible to send a faster than light signal using this phenomenon, so that's not what I'm asking ...
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167 views

Are all instances of quantum non-locality problem artifacts of the use of classical concepts in quantum physics?

Consider experiments involving entangled spins, say two-spin 1/2 particles in the singlet state: $$\left|\psi\right> =\frac{1}{\sqrt{2}}\left[\left|\uparrow\downarrow\right> - \left|\downarrow\...
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50 views

Dimension of joint probability space in the Bell Scenario

In the Bell(CHSH) scenario with the normal two qubits+two measurement settings, how does the dimension of the joint probability space $ P(ab|xy)$ drops from 16 to 8? In general, for two d-dimensional ...
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297 views

Why Shy away from non-local nature of gravitational energy/momentum? [closed]

Feel free to tear me a new one, This is something that has been bothering me a while. The very nature of attempting to write gravitational energy/momentum (called the stress energy pseudotensor), ...
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1answer
284 views

Local and non-local counterterms in the ultraviolet and infrared limits of a quantum field theory

These is a question about the renormalization of a quantum field theory. See below equation (19.3) in page 176 of Thomas Hartman's notes on Quantum Gravity and Black Holes. When we renormalize a ...
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55 views

Does Bell's theorem include causal networks?

I am not an expert, so by causal networks I mean whatever it is that Wolfram talks about in its book. Regardless of the official definition, it basically means that spacetime is an emergent property ...
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1answer
296 views

Why infinite order derivative in Lagrangian density implies non-local?

There is a homework in field theory. It says that negative order of derivative( such as $\frac{1}{\nabla^2}$), fraction order of derivative ( such as $\nabla^{2/3}$ ) and infinite order derivative in ...
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241 views

Difference between PR correlations and entanglement correlations?

(As pointed out by helpful users, one of the bolded claims is interpretation dependent. Therefore, unless otherwise specified, Copenhagen interpretation is used throughout) Recall that for classical ...
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1answer
263 views

Does a state need to be entangled for it to produce nonlocal correlations?

I was reading the Wiki on quantum non-locality and saw this near the bottom: While it is true that a pure bipartite quantum state must be entangled in order for it to produce nonlocal correlations,...
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949 views

If Pilot Wave Theory is non-local, how does the pilot wave change over time?

My understanding is that Bohmian Mechanics (pilot wave theory) is non-local, meaning that effects propagate faster than light. Are these effects in fact instantaneous in that model? How would an ...
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178 views

Entanglement = Steering = Non-Locality?

For a simple case of two party system. What I understand by Entanglement(please correct me if I am wrong) is that if some property of the two systems is entangled, then knowing one, provides the ...
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232 views

What evidence is there that The Big Bang was not just a local phenomenon?

This post is the second in a series of posts that met (decreasingly) with some contention from the physics community, do to my status as a pure mathematician at the very beginning of trying to discuss ...
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458 views

Could quantum entanglement be explained in terms of synchronized chaos?

Most arguments against any hidden variable theories in quantum mechanics are based on Bell's theorem and consequences. In the proof of Bell's theorem, there is a hidden assumption related to the ...
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169 views

Why can we always define the Lagrangian Density this way?

Learning some field theory, and many authors just claim "it is nice to express the Lagrangian as an integral $L = \int\mathcal{L}\,\mathrm{d}^3x$." Now I understand when dealing with fields, the sum's ...
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82 views

Non-linear bell's inequality?

Consider the Bell setting, where Alice and Bob get inputs $x,y$ and they perform measurements $\{M^x_a\}_a,\{N^y_b\}_b$ respectively on their shared pure state $\Psi_{AB}$ to obtain outputs $a,b$. ...
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Quantum Mechanics Vs nonlocal causality

There is an article in Physics world.com dated August 18, 2016, titled "Quantum Mechanics Trumps Nonlocal Causality. The author of the article Philip Ball quotes one of the experimenters ( i.e. ...
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158 views

Seeking clarification about a discussion of the Holographic Principle in Sean Carroll's book

I am reading Sean Carroll's pop-science book 'From Eternity to Here' and am having trouble connecting the links in his discussion of the Holographic Principle. At the outset, I would ask that you try ...
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Bell's theorem and fluid-mechanical experiments using droplets: are local hidden-variable theories possible after all?

Recent fluid-mechanical experiments by the groups of Couder in Paris and Bush at MIT, mimic a surprisingly wide range of quantum effects. The essential ingredient of these fluid-mechanical systems is ...
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125 views

Quantum non-locality with commuting measurements?

We consider the Bell scenario, in which Alice and Bob share an entangled pure quantum state $\mid \Psi \rangle_{AB}$. Alice gets an input in the set $\{1,2\ldots X\}$ and Bob gets an input in the set ...
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Non-local cosmology

Does anyone know what exactly non-local cosmology mean? Does it have anything to do with the scale we are dealing with or is it just the idea of objects interacting with each other despite having very ...
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211 views

How is locality preserved in quantum mechanics?

I was reading this post: http://motls.blogspot.com/2015/06/locality-nonlocality-and-anti-quantum.html Specifically here: "There is no nonlocality. There is no action at a distance. There is no doubt ...
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254 views

The link between non-locality and Heisenberg's uncertainty relations

I have recently found out1 that the concepts of non-locality and Heisenberg's uncertainty do not live independently of one another in Quantum Mechanics. In other words, roughly the idea goes as: the ...
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The entanglement of a two dimensional particle and the one of two one dimensional particles

Case 1: Usually, entanglement is a correlation between more than one particles. For example, the momentum $p_1$ of the particle $1$ and the one $p_2$ of the particle $2$ have the relation that $p_1 +...
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277 views

What stands behind the quantum nonlocality appearing in entanglements, and why Bell's inequalities are violated?

I noticed the question whether Bell's inequalities are based on a false premise, (https://physics.stackexchange.com/questions/219904/could-bells-theorem-be-based-on-a-false-premise) but I bring ...