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3
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1answer
113 views

About the nonlocality of QM and faster-than-light/backward-in-time machines

The fact the quantum mechanics is nonlocal is known already for a long time, since the Bell works (1966 and later) and the Aspect's group experiments confirming the Bell-type CHSH inequality (1980 ...
1
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3answers
146 views

Non-locality in non-relativistic Quantum Mechanic

I guess the following obvious question is answered by any flavor of relativistic Quantum Mechanics, but I just wanted to check whether I understand correctly: Is it correct that nonrelativistic QM ...
1
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0answers
100 views

Does Hardy's paradox represent a proof against Bohm's interpretation of the quantum mechanics?

This is a thought-experiment, see "Quantum Mechanics, Local Realistic Theories, and Lorentz-Invariant Realistic Theories", Phys. Rev. Lett., Vol. 68, No. 20, page 2981, year 1992, that rules out local ...
1
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0answers
39 views

What does “nonlocal in time” mean?

I am studying MOND theory. At some point Milgrom says the theory needs to be nonlocal in time in order to enjoy Galilei invariance, but I don't understand the meaning. Which are the major ...
2
votes
1answer
71 views

Are there any experimental tests of non-locality / Bell inequalities that do not rely on spin?

All the experiments I know, which have been performed to test Bell inequalities, are somehow based on measuring the spin degree-of-freedom of some particle (usually photons, sometimes electrons). I ...
0
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0answers
25 views

Could non-locality imply a holographic universe?

I am just a physics groupie, so please excuse me if this is stupid. But wouldn't non-locality possibly imply a holographic universe? An analogy would be a projector and a hologram-- if a change occurs ...
0
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2answers
73 views

Question on the logical structure of the EPR argument and Bell's inequalities

Recently I have read a lot online about the EPR argument and Bell's inequalities and its implications. When comparing what people write there online with the actual research articles of Einstein and ...
9
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2answers
88 views

Natural entanglement system

I'm beginner and amateur interested by the quantum physics. I would like to know if it exists entanglements systems at natural state or it requires mandatory an human intervention ? Is it possible ? ...
2
votes
1answer
121 views

Local versus non-local functionals

I'm new to field theory and I don't understand the difference between a "local" functional and a "non-local" functional. Explanations that I find resort to ambiguous definitions of locality and then ...
4
votes
2answers
95 views

Non-local structure of field theory

Can someone explain what is non-local structure of field theory? I know you cannot have $\phi(x) \phi(y)$ term in Lagrangian which indicates the non-locality. However, why I cannot have the non-local ...
0
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0answers
28 views

Exhaustive list of assumptions for the Clauser-Horne-Shimony-Holt inequality

I am trying to create an exhaustive list of all assumptions which work as the base of the CHSH inequality. Locality - this means an object can be influenced only by its surroundings. So, the events ...
2
votes
4answers
302 views

Local EPR-experiments with photons in vacuum?

The principle of non-locality states "that an object is influenced directly only by its immediate surroundings." (Wikipedia) When two entangled particles are measured in an EPR experiment, we ...
0
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3answers
110 views

“Spooky action at a distance” or particle correlation at the time of their creation?

In Bell test experiments, two particles that are a singlet are measured and are found to be correlated. The correlation leads us to believe that they are somehow connected non-locally: the ...
3
votes
1answer
165 views

Non-Locality of Space - QFT (Srednicki's book)

I was going through Mark Srednicki's book on QFT. It says in the relativistic limit the Schrodinger equation becomes something like : $$ i\hbar\frac{\partial}{\partial t} \psi(\vec x,t) = ...
1
vote
1answer
171 views

What is meant by a local Lagrangian density?

What is meant by a local Lagrangian density? How will a non-local Lagrangian look like and what is the problem that we do not consider such Lagrangian densities?
3
votes
2answers
253 views

Why does the Dopfer EPR experiment require coincidence counting?

Dopfer Momentum-EPR experiment (1998) seems to provide a interesting tweak in the EPR experiment. To read more details on this experiment, see: ...
2
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0answers
51 views

Pseudo-randomness of observables

There is a somewhat recent paper by Colbeck and Renner that, given the assumptions — 1) QM accurately predicts the correct statistical results in experiment (which so far has always been found to be ...
1
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0answers
66 views

Nonlocal games: The CSCH game

The problem that I am having is that I don't see how they come up with the probabilities mentioned on Slide #7 here: https://www.ipam.ucla.edu/publications/opws1/opws1_9367.pdf first I don't ...
1
vote
2answers
159 views

Non-locality and Bell's theory

Non-Locality – (just ) one more question? I have read comments that Bell’s theory proves quantum mechanics is non-local, and also comments that it does not. I have read a comment by a very eminent ...
1
vote
1answer
155 views

Dimension & non - locality problem in string theory

I have some questions with string theory: Why is it that there is exactly 4 large spacetime dimensions while the rest remain small? It is a nonlocal QFT. How could that fit in GR?
4
votes
2answers
212 views

Non-local Lagrangian contact interaction

Conside a contact interaction given by a delta function on their worldlines. Use a gauge fixed Lagrangian for two point particles in terms of their proper times $t$ and $t^{\prime}$. Is it possible to ...
2
votes
1answer
73 views

Is it possible to determine the state or values of something without measuring it

To give context to this question, I am currently looking into non-locality / hidden variables / Bell's Theorem, EPR / etc. I've noticed the assertion that the values / state of something when ...
8
votes
1answer
290 views

Is this field redefinition for free scalar field theory non-local?

The action of free scalar field theory is as follows: $$ S=\int d^4 x \frac{\dot{\phi}^2}{2}-\frac{\phi(m^2-\nabla^2)\phi}{2}. $$ I have been thinking to redefine field as ...
3
votes
1answer
155 views

Definition of Local Function

Now a days I am studying Srednicki's QFT book. In its third chapter it is written that Any local function of φ(x) is a Lorentz scalar, [...] . Now my question is: What is a local function?
4
votes
1answer
544 views

Is spacetime an illusion?

In consistent histories, for gauge theories, can the projection operators used in the chains be not gauge invariant? In quantum gravity, for a projection operator to be gauge invariant means it has ...
2
votes
1answer
363 views

How to tell local and non-local in QFT?

I'm taking QFT course in this term. I'm quite curious that in QFT by which part of the mathematical expression can we tell a quantity or a theory is local or non-local?
11
votes
1answer
146 views

CHSH violation and entanglement of quantum states

How is the violation of the usual CHSH inequality by a quantum state related to the entanglement of that quantum state? Say we know that exist Hermitian and unitary operators $A_{0}$, $A_{1}$, ...
8
votes
1answer
47 views

Sub and super multiplicativity of norms for understanding non-locality

In relation to various problems in understanding entanglement and non-locality, I have come across the following mathematical problem. It is most concise by far to state in its most mathematical form ...
20
votes
2answers
109 views

Bell polytopes with nontrivial symmetries

Take $N$ parties, each of which receives an input $s_i \in {1, \dots, m_i}$ and produces an output $r_i \in {1, \dots, v_i}$, possibly in a nondeterministic manner. We are interested in joint ...
15
votes
4answers
78 views

Why can't noncontextual ontological theories have stronger correlations than commutative theories?

EDIT: I found both answers to my question to be unsatisfactory. But I think this is because the question itself is unsatisfactory, so I reworded it in order to allow a good answer. One take on ...
16
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3answers
2k views
5
votes
1answer
197 views

If strings are infinitely extended, are they nonlocal?

To completely localize a string within any bounded region of space, no matter how large, requires an infinite energy. Does this mean strings modes are inherently nonlocal?