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Non-locality of the wavefunction in QM and Twistor theory [closed]

Regarding locality, I don't think locality is a principle per se, but we often assume that the physical fields are local on spacetime, describable by partial differential equations and so on. But of ...
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Bohmian mechanics, Leggett inequality, realism and nonlocality

Very often it is said that the Bell inequality has ruled out the possibility of hidden variables (HV) in QM. This is incorrect since Bell inequality has ruled out local hidden variables: nonlocal HV ...
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EPR effect, non-locality, positivism and realism

In the framework of EPRB experiments, has an experimental verification been performed of the conservation of 2-time correlations of Bob's photons polarization despite Alice's polarization measurements?...
ABC's user avatar
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Relativistic Schrödinger Equation: How is it relativistic and can it be useful? [duplicate]

As is well known, the usual Schrödinger equation, $$\mathrm{i}\hbar\frac{\partial}{\partial t}\psi=-\frac{\hbar^2}{2m}\Delta\psi+V\psi,$$ is not relativistic. It can be derived formally by applying ...
Caesar.tcl's user avatar
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Measurable effects of the global structure of the SM

It is known that the Lie algebra of the SM is $$ \mathfrak{su}(3)\oplus \mathfrak{su}(2)\oplus \mathbb{R}\,, $$ so that the Lie group is $$ G_{\text{SM}} = \dfrac{SU(3)\times SU(2) \times U(1)}{\Gamma}...
Gabriel Ybarra Marcaida's user avatar
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2 answers
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How can the quantum state of one particle depend on the other in entanglement without non-locality? [duplicate]

There are many different interpretations of quantum mechanics. Some posit determinism and non-local influences between particles. Others do not, such as in the Copenhagen interpretation. My question ...
user avatar
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4 answers
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Could reducing entanglement by unitary operations allow for FTL-communication? (and why not?)

About the closure: This Question is about why manipulating 1 particle of an entangled pair unitarily can’t cause measurable consequences on the other and how this manifests in the concretely described ...
Zaph's user avatar
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Can a non-local theory be consistent with special relativity?

If there was a non-local theory that explained quantum entanglement correlations, does it follow that it would violate special relativity?
Hume's user avatar
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4 answers
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All the logically possible ways to get around Bell-type inequalities

I'm a high school student, so my (mis)understanding here is not very rigorous or precise, but I will write it below so as to concretely frame my question: Bell's theorem takes three assumptions ...
user110391's user avatar
4 votes
4 answers
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Do Bell’s inequalities assume determinism?

I was watching a video of Tim Maudlin where he talks about how the CHSH version of Bell’s inequalities do not assume determinism and only assume locality. He said that it is a common misconception ...
inquisitive 's user avatar
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2 answers
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Why do particles need a signal to travel to another to affect it? [closed]

I was reading up on quantum entanglement, non locality, and how people interpret QM to still be local in the sense that it does not allow for faster than light communication signals. I have two ...
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How do non-local correlations occur in QM without a cause? [closed]

The Copenhagen interpretation of QM ultimately amounts to asserting that non-local correlations occur without a cause since that cause would involve propagation of information faster than the speed ...
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2 answers
118 views

Does local realism imply entangled photons are equal (or opposite)?

I'm watching a video about Bell's inequality and how there can be no local hidden variables. They explain it using photons and whether they pass through a polarizer or not when they're oriented at ...
Juan's user avatar
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6 answers
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What was the fallacy in EPRs chain of arguments?

Let's say, there is an entangled system of two electrons with opposite spins; The joint system is in a state of eigenvectors for z-Spin ( $S_z$) with both particles far away from each other: $$|\Psi\...
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Learning contextual data using a variational quantum circuit

This question is about contextuality in quantum mechanics, about non-quantum data also showing contextuality. Definition for the specifics of the question as well as an example of contextuality in ...
TheStressTensor's user avatar
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2 answers
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What is the consensus among physicists on whether quantum mechanics has non-locality? [closed]

According to this article here by the SEP, Following Bell's work, a broad consensus has it that the quantum realm involves some type of non-locality (for examples, see Clauser and Horne 1974, Jarrett ...
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What does non-local transport mean in plasmas physics?

I found a lot of plasma physics works that talks about non-local transport, what is non-local transport in plasmas? What does non-local transport mean ? Some examples please.
Gallagher's user avatar
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Newton's second law - local laws and non-local laws

What are local laws? I was reading this line in a book... Newtons second law is a local law. This means that it applies to a particle at a particular instant without taking into consideration any ...
Aditi Bansal's user avatar
2 votes
1 answer
171 views

Quantum Mechanics without Complex Numbers in a multipartite setting

I was fairly convinced that usual QM formalism didn't necessitate the use of complex numbers and that ultimately they're just a matter of convenience and utility rather than anything fundamental. This ...
greatscissors's user avatar
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1 answer
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Contradiction of propagation speed of gravitational waves with non-locality of gravity?

Although LIGO at 2016 verified the speed of a traverse gravitational wave being the speed of light in a vacuum $c$ there is also the fact that gravity is a non-local phenomenon, meaning that it is not ...
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Justification for the derivative expansion in the Exact Renormalization Group

In the Exact Renormalization Group formalism, specifically the formalism of Wetterich, one writes down an evolution equation for the effective average action $\Gamma_k[\varphi]$, see f.ex $$ \...
Martin Johnsrud's user avatar
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Difference between local and non-local optical model potential?

As far as I understand, local OMP (optical model potential) depends only on the relative position, and non-local OMP depends on relative position and momentum. I am searching for more information so ...
Virender Ranga's user avatar
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0 answers
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Can a point in the quantum set of correlations violate more than one independent facet Bell inequality?

Usually, depictions of the quantum set of correlations and the local polytope look something like: In this image it looks like non-local points belonging to the quantum set (in yellow) violate only ...
neilps2000's user avatar
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2 answers
174 views

Is the possible Bell's test loophole of entangled particles communicating at a non instantaneous but FTL speed addressed and eliminated? [closed]

TLDR: There seems to be a loophole in Bell's test that is not addressed or eliminated before we can successfully conclude that it proves that the Universe is unreal and non local. The entangled ...
Hari Kumar's user avatar
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1 answer
236 views

How can we be sure Bell's theorem disproves local realism when we are not sure whether the measuring apparatus is in some form of entanglement or not? [duplicate]

Bell's therorem seems to disprove localism because measuring, let's say spin of an entangled electron, seem to communicate the measurement to it's another pair instantaneously. But isn't another thing ...
Hari Kumar's user avatar
2 votes
1 answer
78 views

Are field theories where free energy density depends on 2nd-order derivative non-local?

It is accepted that infinite order of derivatives in field theory lead to non-local effects while finite number of them local. reference within physics stack exchange Let’s take a lattice with next-...
Sudipta Nayak's user avatar
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Is there any limit to the utility of quantum measurements in the sense of a Lieb-Robinson bound?

So the Lieb-Robinson bound of 1972 derives an emergent maximum speed $v \ll c$ of the propagation of quantum information under time evolution generated by some local Hamiltonian $H(t)$. Basically, ...
just a phase's user avatar
2 votes
3 answers
248 views

Does non-local hidden variable theory predict the outcome of an experiment? [duplicate]

I am trying to understand what decides the outcome of an experiment and if there is any theory (e.g. non-local hidden variable theory) that is able to predict the outcome.
Rajaram Venkataramani's user avatar
-1 votes
2 answers
274 views

Quantum Entanglement: Is Non-locality Inherent or Does It Violate Causality? [duplicate]

Dear Physics Stack Exchange community, I am intrigued by the concept of quantum entanglement and its implications for our understanding of the fundamental nature of reality. I have come across various ...
Raihan Sarker's user avatar
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Why does it make sense to add/subtract the results of measuring in 2 different bases in Bell's inequality when each observer only measures 1 property?

In the CHSH inequality, we construct an experiment whereby two observers each receive a particle and measure two given properties of their particles, for which the outcomes are ±1. We then consider ...
David's user avatar
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Does a measurement violate conservation law? [duplicate]

(Edited according to the discussion with @naturallyInconsistent. The edited part is highlighted in italic.) We have an experimental bench and we assign a coordinate system $(x,y)$ to it. We shall call ...
Leo's user avatar
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1 answer
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Does a nonlocal deterministic hidden variable theory imply retrocausality?

I've had this idea for a while, and recently I stumbled upon a short paper from N. Gisin that formulated this idea, but I could not find a meaningful discussion on the problem. The paper that I found ...
cognition's user avatar
-2 votes
2 answers
210 views

What's mechanism of "spooky action at the distance"? [duplicate]

Nobel prize 2022, a local theories of hidden variables are ruled out, Einstein's "spooky action at a distance" seems to be a reality. Is there ANY explanations of this behavior of quantum ...
ZZ Wave's user avatar
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1 vote
1 answer
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Have spin-correlation experiments been done on entangled particles other than photons?

I know that Bell experiments on spin correlations have been done with entangled photons, but have spin-correlation experiments ever been done on entangled particles other than photons?
pete's user avatar
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0 answers
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How can two phonons be entangled when the atoms in the crystal are not?

It is my understanding that you can use phonons to make a gaussian packet, which would behave like a quantum particle. I also believe that you can make two such packets and entangle them, that is ...
pajaro gamboa's user avatar
2 votes
3 answers
1k views

What is the difference between nonlocality and entanglement?

I'm a bit confused about the difference and relation between (quantum) nonlocality and entanglement. To give some context about my confusion, I was reading this paper: Brunner, Nicolas, et al. "...
jay's user avatar
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1 vote
1 answer
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Is degeneracy of eigenvalues required for the Kochen-Specker theorem?

I'm wondering why the operators for the Kochen-Specker theorem are 3-dimensional while they only produce two eigenvalues $\{0,1\}$. Is this degeneracy always needed regardless of the dimensionality of ...
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1 vote
2 answers
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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{\...
NeonGabu's user avatar
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0 answers
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Local fields in relativity with pure creation operators

The Wikipedia page on the Spin-Statistics theorem states that In relativity, there are no local fields that are pure creation operators or annihilation operators. In this answer at SE Phys, in a ...
Lucas Baldo's user avatar
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7 votes
2 answers
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Are spinors intrinsically nonlocal?

I would prefer a purely classical answer since I don't think quantum mechanics (quantum field theory etc.) are necessary to answer this question and such answers will likely complicate matters. If you ...
Jagerber48's user avatar
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3 votes
1 answer
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Nonlocality of a bug on movie screen

I am currently learning quantum mechanics using Griffiths. In the appendix, he goes to talk about EPR and Bell's inequality, and that experimental verification of Bell's inequality rejects the "...
Davidson Cheng's user avatar
2 votes
0 answers
259 views

How localized are photons in a quantum field?

Are photons or other quanta at least somewhat localized in a quantum field? My limited understanding of quantum field theory is that photons or other fundamental particles (quanta) are excitations of ...
kdtop's user avatar
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6 votes
2 answers
840 views

In the Bell CHSH experiment, why are Alice and Bob not allowed to pre-arrage their measurements?

From Nielsen and Chuang, Chapter 2: Imagine we perform the following experiment, illustrated in Figure 2.4. Charlie prepares two particles. It doesn’t matter how he prepares the particles, just that ...
Bard's user avatar
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-1 votes
2 answers
299 views

Quantum mechanics: does many-worlds interpretation remove nonlocality? Bell-type experiment

Trying to make sense of many-worlds interpretation and see if it removes nonlocality or solves other problems. It appears to me that branching is equivalent to collapse... so trying to see what I'm ...
Ameet Sharma's user avatar
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1 vote
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How are the different derivations of Bell's inequality related?

I wanted to ask about two different derivations for bell's inequality for the known CHSH inequality. One derivation is the one bell originally used in 1971 this derivation is thoroughly written in ...
Tomer Gigi's user avatar
4 votes
2 answers
290 views

Why is quantum non-locality so surprising when quantum mechanics is a non-relativistic theory to begin with?

Ignore the fact that Quantum Field Theory (QFT) is compatible with Special Relativity (SR) for a second. Imagine we are back in a time before the construction of QFT. If Quantum Mechanics (QM) is the ...
Relatively General's user avatar
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Is there any way to write a non-local operator nicely?

Consider the boundary(the real axis) of the 2d CFT or the D-brane. They were non local object but with well known description. Consider the following expression, $$\langle 0| \phi_1(z_1) \phi_2(z_2)|B\...
ShoutOutAndCalculate's user avatar
2 votes
1 answer
245 views

Measurement of the spin of the EPR pair in two orthogonal directions and how did Einstein tackle this?

Let us consider two types of measurement in the EPR experiment. In Bohm's description of this experiment, the state of the electron-positron (called the EPR pair) is given by $$ |{\rm EPR} \rangle =\...
Solidification's user avatar
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0 answers
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Nonlocal Gravitational energy: How to localize nontrivial topology in GR?

Ok, This question has been beaten to death. I just wanted to look at it from a slightly different angle: Einstein, Rosen, and later Wheeler considered the possibility of particles as spacetime ...
R. Rankin's user avatar
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1 vote
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Non-local Euler-Lagrange equations and Noether theorems

Following up my Noether theorem issues: how can Euler-Lagrange and Noether theorems be formulated for non-local lagrangians? Two examples from the literature: Example 1. Let $L(\phi, F(\phi))=-\dfrac{...
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