Locality Definition and 83 Threads

Hi, I have a conceptual question concerning causality and locality in QM. Causality plays a role in second quantization when doing QFT, which one calls "micro-causality"; the commutators between fields disappear when the interval between them is spacelike. However, how does this fit in...

The term "manifest locality" keeps being used, eg. in talks by Cachazo http://pirsa.org/10080013/ and Arkani-Hamed http://online.kitp.ucsb.edu/online/bblunch/arkanihamed/ . In Hamiltonian QFT, "locality" means Lorentz invariance, and is implemented by requiring that spacelike field operators...

Let me pose a brain teaser for those who believe that they understand quantum (non)locality, Bell, EPR, as well as logic, very well. :wink: Assume that quantum mechanics is correct (i.e., that future loophole-free experiments will confirm violation of Bell inequalities). Consider 2...

Can someone explain to me "Locality" in field theory? I know that two fields have to commute at space-like separations so that observations don't affect each other at these separation. what about the thing where the Lagrangian can't couple fields at different locations and time, is it so...

It seems everyone think that Bell Inequalities rules out any hope of ever getting a local and deterministic account of reality. This need not be so... Gerard 't Hooft (Nobel Prize winner of 1999) has been working on a theory that may explain the quantum behaviour in a classical way...

What is "passive locality"? Bell's Theorem. In a current thread about explaining Bell's theorem, the question of "passive locality" came up. "Passive locality" was introduced by Nelson in 1986. After discussions with Bell he distinguished between "active" and "passive" locality, arguing...

Quantum Entanglement allows spatially separated entangled particles to have impact on each other instantly (overcoming the allowed speed-limit of causal influence which is 'c'). How does Quantum Field Theory address this problem (protecting causality and chronology)?

I’m starting to think this idea would defy the Bohm interpretation enough to be distinct. Can I call it Retropilot? I’m thinking the pilot wave can be modified in a way that maintains both locality and causality. I’m sure this idea has been discussed here and it’s likely I’m missing some obvious...

Freidel will be giving a talk in the online seminar ILQGS, about Relative Locality---the subject of this paper: http://arxiv.org/abs/1101.0931 The principle of relative locality Giovanni Amelino-Camelia, Laurent Freidel, Jerzy Kowalski-Glikman, Lee Smolin 12 pages, 3 figures (Submitted on...

Locality and non locality? Hi... What means locality and nonlocality ??

I am opening a new thread to continue discussion of some interesting ideas around EPR and Bell. Specifically, this is about the idea of realism, and whether it is tenable in light of Bell and other HV no-go theorems. Note: I usually use Hidden Variables (HV) and Realism interchangeably...

== http://arxiv.org/abs/1004.1780 == III. TRANSITION AMPLITUDES In a general covariant quantum theory, the dynamics can be given by associating an amplitude to each boundary state [32, 33]. Therefore, the dynamics is given by a linear functional W on H. The modulus square P(ψ) =...

Claim 1: If \psi(x,0) has a compact support, and i\partial_t\psi(x,t) = -\partial_x^2 \psi(x,t), then \psi(x,t) does not have a compact support for any t>0. Claim 2: If \psi_1 and \psi_2 are the same in some environment of a point x_0, then \partial_x^2 \psi_1(x_0) = \partial_x^2...

Matter as topological entropy (Fotini disordered locality) I have to go in 5 minutes or so, but will get back to this. Fotini M. has this scheme or picture of disordered locality. The root meaning of topology is locality. Disordered locality is disordered topology. Topological entropy. I...

What does it mean to say that the propagator G(x,x')=\int \frac{d^4p}{(2\pi)^4}\left(\frac{e^{ip(x-x')}}{p^2+M^2}\right) is nonlocal? Does that mean that if x and x' are space-like in separation, this expression is non-zero? If you did have something local represented by a Fourier...

Some papers on foundations of quantum mechanics distinguish the notions of locality and separability (or non-locality and non-separability). Can someone explain to me what is the difference between locality and separability? Or can someone point to a reference where this difference is explained?

how do physicists solve this contradiction (when information moves faster then the speed of light)? thanks

A couple of articles showed up in the Arxiv today regarding aspects of Quantum Locality (as opposed to quantum non-locality). In essence, both theoretically and experimentally, these attempt to show that QM and Special Relativity are compatible and there is no quantum non-locality. Neither of...

I would like to get some opinions from those of you who prefer a One-World interpretation of QM (CI,Bohm,Transactional,Relational, etc) about the following: 1) I understand it is already clear that QM puts a limit on our ability to predict the future. But if you believe that the universe is a...

Locality of interaction: We assume that the the influence that one particle has on another cannot be transmitted instantaneously (why not?). It does not have to be photon at light speed as in one electron exerting a force on another electron. How does one electron 'know' of the existence of...

Ok. There are some concepts here that I am having trouble reconciling. I would first like to "stipulate" that for time to have any meaning, there has to be change. I'm not sure if there is some Brownian motion at 0 Kelvin, but for the sake of argument, let's say it is not. So, if I freeze an...

my thoughts on "Quantum Graphity: a model of emergent locality" I want to thank Marcus for bringing this to my attention. One thing I've wanted to see is a rigorous derivation of Wen's string net condensation, which gives rise to both U(1) gauge charge and electrons, with LQG's spin...

I believe I read that the Everett Many Worlds Interpretation resolves the apparent locality problems with entanglement (i.e. the necessity of a faster-than-light influence to explain the correlations between the behavior of entangled particles). If so I'm not sure how. MWI says that the...

Hi! For some moths ago I was thinking on the significance of the EPR-paradox and I think I have found a new way to tackle the refutation of locality in QM that was presented by Einstein, Rosen and Podolsky. The whole principle of my idea is the treat time in the exactly same way as we treat...

Ref: http://en.wikipedia.org/wiki/Principle_of_locality" I don't have this article, so my first request is that if anyone has it and can either post it or (if concerned about copyright issues) you could email it to me, that would be appreciated. I may need it as a reference for a paper I'm...

consider the Doppler shift formula f=f'gamma(1+betacostheta). (1) the measurements of f and f' are associated with the measurement of time intervals, during which, depending on the scenario we follow, beta and theta could change. authors say that using (1) we make the "locality" assmption in...

I've argued here in the past (with dr chinese and others) about what, exactly, is proved by Bell's Theorem. Here is a new paper which addresses and clarifies many of those points: http://www.arxiv.org/abs/quant-ph/0601205 I suspect it will be of interest to people here. But before...

Are there groupd of animals that are veryvery 'local' ? if another animanl lives in that local-breained comnity ? What will happern ? Will that animal die ?

In trying to grasp the Bell Theorem that "reality must be non-local" I have a question---what exactly does it mean to say that two physical objects are "local" vs "non-local" in their interactions ? In reading Nick Herberts book, (1985), Quantum Reality, he states that local interaction =...

Does a Quantum System know about an observer before the Observer can know about the Quantum System? Quantum domains are small, Macro Domains are larger,so when one looks from a Macro Domain to one that is smaller(Quantum) one first has to locate the Quantum System to be observed, then because...

Can someone explain the mathamatics behind locality and nonlocality?

-- -- EPR experiments seem to show a significantly higher correlation rate in the detection of separated photons which are in an entangled state. From the measured correlation we may or may not want to draw very fundamental conclusions. One such a far reaching conclusion would be that...

My own simplistic definitions: Locality-What happens here does not affect anything anywhere else in the universe whether there exist a reference frame or not. Nonlocality-What happens here is related to everything everywhere else in the universe. Quantum entanglement shows perfect...