Talk:Lorentz covariance
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[edit] Clarification
Note: this usage of the term covariant should not be confused with the related concept of a covariant vector. What does this statement mean, exactly? -- Decumanus | Talk 06:46, 22 Mar 2004 (UTC)
- Strictly speaking, covariant vectors are vectors living in a cotangent space of some manifold. In general relativity, a covariant 4-vector is, in fact, a Lorentz covariant quantity, but so is a contravariant 4-vector — which is a little confusing. Nonetheless, the terminology is standard. -- Fropuff 06:51, 2004 Mar 22 (UTC)
- O.K. I thought you meant something like that, but I wasn't sure from the phrasing. Perhaps something like this should be in the article itself. -- Decumanus | Talk 06:55, 22 Mar 2004 (UTC)
[edit] Mistatement
I don't think this is true. One can imagine a non-uniform universe in which Lorentz covariance is true.
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- Lorentz covariance is part of a broader concept of cosmological principle, that the universe, when viewed on sufficiently large distance scales, has no preferred directions or preferred places. Poincaré covariance is the extension to the Poincaré group.
Roadrunner 02:22, 23 Jul 2004 (UTC)
[edit] Comprehensible? I don't think so.
This article is quite impossible to understand unless you have a degree in physics. Couldn't we add something like "Imagine a volleyball match, where the ball contiuously moves between... " or something like that to all the "Due to the ambiguity and indifference of the Lorentz-Eintein-Buggyman co-ordinated octopus, the Buron and Woron particles behave similarly due to the incoprehensible... " type paragraphs? —The preceding unsigned comment was added by 203.122.73.116 (talk • contribs) 09:22, 23 June 2005 (UTC).
Addendum by another person: Suggestion on how to make this article better
Choose as the target audience a college freshman with exposure to the ideas of special relativity. Define very clearly (with a link) the notion of an *in*variant quantity like spacetime distance between two events. (The existing article starts off in this direction but...) Proceed to define *co*variance in that context. The important thing that is missing is the sense of how and why covariance is distinct from invariance. Include a technical definition but keep the target audience / comprehensible language requirement in mind. When done reading it, they should be able to say more than 'covariance is like invariance; but I can't tell you how it's different.'
Finally suggest providing a clear and specific example in a separate sub-section. —The preceding unsigned comment was added by 192.92.90.66 (talk • contribs) 21:25, 16 January 2006 (UTC).
[edit] NPOV for Loop Quantum Gravity section
I am convinced that such a (misleading) discussion of LQG, one particular theory that has problems with Lorentz covariance, much like with many other requirements, does not belong to the page about such an important topic as Lorentz invariance. It's not just my opinion, see also Prof. Sean Carroll, [1]. All the best, Lubos --Lumidek 11:46, 26 October 2005 (UTC)
- I whole heartedly agree. Can we move this material to a separate article (or merge it into the Loop quantum gravity article)? -- Fropuff 15:16, 26 October 2005 (UTC)
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- It came from loop quantum gravity, a while back, when that needed concision. I suggest a separate page for the issue. Charles Matthews 16:02, 26 October 2005 (UTC)
[edit] Why "Non-Graviational?"
It would be nice if somebody could explain why gravity is exempted from this rule. —The preceding unsigned comment was added by Megacz (talk • contribs) 11:33, 8 January 2006 (UTC).
- Because gravitational physics does not obey Lorentz covariance; general relativity is the present standard theory of gravitation that uses general covariance (a 'generalisation' of Lorentz covariance). Hope this helps. MP (talk) 12:30, 8 January 2006 (UTC)
[edit] To merge or not to merge?
- I'd say yes (Lorentz symmetry), not that there is much here to merge.---CH 00:41, 20 March 2006 (UTC)
- Yes, and also Lorentz violation should be merged. It is hard to understand a complexity of topic, if they are chopped into such a small pieces. Hidaspal 13:27, 28 April 2006 (UTC) --> Done. Hidaspal 14:04, 28 April 2006 (UTC)
[edit] Is this even true?
I quote from the article:
- "Lorentz covariance requires that in two different frames of reference, located at the same event in spacetime but moving relative to each other, all non-gravitational laws must make the same predictions for identical experiments."
I'm fairly certain this isn't true on at least two accounts. Firstly, Lorentz covariance applies only to two different inertial frames of reference. And secondly, not all predictions are the same: even in Galilean relativity, we predict different values of kinetic energy in different reference frames. The situation is similar in special relativity: various physical quantities (energy, momentum, B-field etc) transform (note this is NOT the same!) as components of various spacetime vectors.
I will be more than happy to make the necessary changes, iff someone agrees with what I've had to say.
--Masud 09:34, 26 September 2006 (UTC)
