Name of general relativity symmetry

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Discussion Overview

The discussion revolves around the search for a term that describes the symmetry distinguishing general relativity from special relativity, particularly in the context of phenomena related to gravity and acceleration. Participants explore concepts related to Lorentz violation, neutrino oscillations, and the Principle of Equivalence, touching on theoretical implications and potential discoveries.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that "Lorentz violating" neutrino oscillations indicate a direct violation of special relativity.
  • Others argue that general relativity is locally Lorentz invariant, and that any effects of gravity on the speed of light or neutrinos do not constitute a violation of special relativity, citing the Shapiro time delay as an example.
  • A participant asserts that neutrino oscillations violating special relativity also violate general relativity, emphasizing that general relativity implies special relativity.
  • There is a discussion about the term for phenomena that violate the symmetry between gravity and acceleration, leading to the identification of the Principle of Equivalence.
  • One participant notes that the Principle of Equivalence is not exact and requires qualifications regarding locality of measurement and interaction.
  • An example is provided regarding the distinction between a charged body on a gravitating body and a uniformly accelerating charge, with implications for radiation and gravitational interactions.
  • Concerns are raised about the limitations of measurements and the potential for distinguishing uniform acceleration from gravity, suggesting that violations of the Principle of Equivalence could indicate significant discoveries.

Areas of Agreement / Disagreement

Participants express differing views on the implications of Lorentz violation and the relationship between general relativity and special relativity. There is no consensus on the terminology for the symmetry in question or the implications of the Principle of Equivalence.

Contextual Notes

Limitations include the need for qualifications regarding the Principle of Equivalence, the locality of measurements, and the distinction between different types of interactions. The discussion also highlights unresolved aspects of how gravity affects measurements and the implications for theoretical physics.

snorkack
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People seem to be seriously looking for "Lorentz violating" neutrino oscillations - meaning direct violation of special relativity.

What is a short name for the symmetry that distinguishes general relativity from special (the symmetry between acceleration and gravity)?
 
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snorkack said:
People seem to be seriously looking for "Lorentz violating" neutrino oscillations - meaning direct violation of special relativity.

What is a short name for the symmetry that distinguishes general relativity from special (the symmetry between acceleration and gravity)?

I don't see the connection between the first part of post and the second. GR is locally Lorentz invariant. Globally (depending on some definitions or conventions), speed of light or neutrinos can be affected by gravity. This is not normally considered an SR violation because it is a consequence of gravity (see Shapiro time delay).

So far as I know, neutrino oscillations that violate SR also violate GR.

It might help if you have a reference to the searches you are discussing.

[You often hear that GR is diffeomorphism invariant. But so is SR. Further, event Newtonian gravity can be expressed in a way that is diffeomorphism invariatn - see Newton-Cartan theory.]
 
So far as I know, neutrino oscillations that violate SR also violate GR.
GR implies SR, so every violation of SR is a violation of GR.
 
mfb said:
GR implies SR, so every violation of SR is a violation of GR.

Indeed. But not vice versa.

What would be the term for phenomena which violate the symmetry between gravity and acceleration?
 
snorkack said:
Indeed. But not vice versa.

What would be the term for phenomena which violate the symmetry between gravity and acceleration?

Ok, now I see: that is the Principle of Equivalence.

It is not an exact principle, without a bunch of qualification (locality of measurement and locality of interaction and not measuring second derivatives of certain quantities).

An example of global interaction is a charged body interacting with its distant field. This distinguishes a charge sitting on a gravitating body (doesn't radiate) from a uniformly accelerating charge (does radiate). [There is some controversy on this, but this is the consensus opinion.] Another, is where gravitational radiation comes into play.

The 'type' of measurement comes into play because curvature does not vanish even at one point; so certain types of devices (theoretical, mostly) could distinguish uniform acceleration from gravity on any scale, however, small. One way around this is to say that acceleration is indistinguishable from 'uniform gravity' which doesn't really exist except as a limit.

In any case, a violation of the principle of equivalence outside of these known limitations would be a major discovery.
 

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