Talk:Principle of locality
From Wikipedia, the free encyclopedia
 |
This article is within the scope of WikiProject Physics, which collaborates on articles related to physics. | |
| ??? | This article has not yet received a rating on the assessment scale. [FAQ] | |
| ??? | This article has not yet received an importance rating within physics. | |
|
Please rate this article, and then leave comments here to explain the ratings and/or to identify the strengths and weaknesses of the article. |
||
"In another use of the term, if we have two observables, each localized within two distinct spacetime regions which happen to be at a spacelike separation from each other, both observables would commute and we have locality." "both observables would commute and we have locality" Unclear what you're trying to say. GangofOne 01:43, 21 July 2005 (UTC)
Regarding the "conventional interpretations" which state that "the actual definite properties of a physical system do not exist prior to the measurement", what does "measurement" mean? Because if it has the standard physical definition of "being bombarded with radiation" then this would not really violate realism in our universe, would it? Since, you know, there is no perfect and energy-free vacuum in our universe. In that case this interpretation really only stipulates that such a system "does not exist" until it is first hit with a photon, which anywhere in the universe should be nigh-instantaneous. Measurement doesn't actually require a consciousness to notice the bombardment. That is simple anthropic arrogance, and it would also be ridiculous metaphysics. --68.251.41.72 12:28, 26 November 2005 (UTC)
Fixed the final paragraph. There is only one sense of "locality," though it is formalized in different ways for different physical theories. Locality is axiomatic to all quantum field theories.
Also, the vast majority of physicists accept that local realism is violated in experiment. At this point, the only way to avoid this conclusion is to invoke previously unknown physical mechanisms that are not supported by other experiments. I changed the wording of a sentence earlier in the article to make this clear. Dave Kielpinski 21:49, 17 December 2005 (UTC)
[edit] Bad syntax "of in" -- please correct
Last sentence reads: This interpretation of the word "locality" is closely related to the relativistic version of in physics.
Someone please correct this - I don't know if it should be "relativistic version of physics" or if there is a word missing. --Smithfarm 20:09, 23 January 2006 (UTC)
[edit] Following two paragraphs edited
WAS:
"In most of the conventional interpretations, such as the version of the Copenhagen interpretation in which the wavefunction is not real, the many-worlds interpretation, and the interpretation based on Consistent Histories, it is realism that is rejected. The actual definite properties of a physical system "do not exist" prior to the measurement and the wavefunction is only interpreted as a mathematical tool used to calculate the probabilities of the outcome of the experiments, which is, in agreement with positivism in philosophy, the only topic that science should discuss."
"In the version of the Copenhagen interpretation where the wavefunction is real, it is the principle of locality that is violated. The wavefunction is a real object that exists prior to the measurement, but the measurement causes the wavefunction collapse which is a non-local process."
IS:
"In most of the conventional interpretations, such as the Copenhagen interpretation wherein the wavefunction has no direct physical interpretation, the many-worlds interpretation, and the interpretation based on Consistent Histories, it is realism that is rejected. The actual definite properties of a physical system "do not exist" prior to the measurement and the wavefunction is only interpreted as a mathematical tool used to calculate the probabilities of the outcome of the experiments, which is, in agreement with positivism in philosophy, the only topic that science should discuss."
"In the Copenhagen interpretation the only physical interpretation of the wavefunction is via the application of Born's Rule that yields a probability density for all regions of space and time. The principle of locality is violated in the measurement process via wavefunction collapse. This is a non-local process since the probability density vanishes everywhere instantaneously, except where (and when) the measured entity is found to exist."
Note: I don't believe there are two Copenhagen interpretations; one where the wave function is real and another were it is not real. Also, the word 'real' is misleading here since the wave function exists in the complex plane and has both 'real' and imaginary parts. The issue is whether the wave function has a direct physical interpretation, and as far as I know, within the CI, it does not. green 65.88.65.217 06:05, 3 February 2006 (UTC)
- Note: After further consideration, I agree that two CI's exist wrt the wf, but referring to them as 'real' versus 'not real' is unclear. I believe I have improved the text in this regard. See most recent edit below. green 65.88.65.217 20:56, 3 February 2006 (UTC)
I edited these two paragraphs again, as follows.
"In most of the conventional interpretations, such as the version of the Copenhagen interpretation where the wavefunction has no direct physical interpretation, the many-worlds interpretation, and the interpretation based on Consistent Histories, it is realism that is rejected. The actual definite properties of a physical system "do not exist" prior to the measurement and the wavefunction is only interpreted as a mathematical tool used to calculate the probabilities of the outcome of the experiments, which is, in agreement with positivism in philosophy, the only topic that science should discuss."
"In the version of the Copenhagen interpretation where the wavefunction is considered to have an unspecified physical interpretation, the principle of locality is violated during the measurement process via wavefunction collapse. This is a non-local process because Born's Rule, when applied to the system's wave function, yields a probability density for all regions of space and time. Upon measurement of the physical system, the probability density vanishes everywhere instantaneously, except where (and when) the measured entity is found to exist. This "vanishing" would be a real physical process, and clearly non-local (faster-than-lightspeed) if the wave function is considered physically real and the probability density converged to zero at infinite distances during the finite time required for the measurement process."
green 65.88.65.217 07:56, 3 February 2006 (UTC)
And again! Here is the latest/current version.
"In most of the conventional interpretations, such as the version of the Copenhagen interpretation where the wavefunction is assumed to have no direct physical interpretation or reality, the many-worlds interpretation, and the interpretation based on Consistent Histories, it is realism that is rejected. The actual definite properties of a physical system "do not exist" prior to the measurement and the wavefunction has a restricted interpretation as nothing more than a mathematical tool used to calculate the probabilities of experimental outcomes, in agreement with positivism in philosophy as the only topic that science should discuss."
"In the version of the Copenhagen interpretation where the wavefunction is assumed to have a physical interpretation or reality (the nature of which is unspecified), the principle of locality is violated during the measurement process via wavefunction collapse. This is a non-local process because Born's Rule, when applied to the system's wave function, yields a probability density for all regions of space and time. Upon measurement of the physical system, the probability density vanishes everywhere instantaneously, except where (and when) the measured entity is found to exist. This "vanishing" would be a real physical process, and clearly non-local (faster-than-lightspeed), if the wave function is considered physically real and the probability density converged to zero at arbitrarily far distances during the finite time required for the measurement process."
green 65.88.65.217 20:39, 3 February 2006 (UTC)
[edit] Relevance of quantum entanglement
There is a link at the bottom pointing to quantum entanglement, which seems highly relevant to this topic, but entanglement is not mentioned in the article at all. Someone please explain how the principle of locality holds up in regards to entanglement.
-
- Explanation added to article --Michael C. Price talk 22:01, 21 June 2006 (UTC)
