Is Doubly Special Relativity Connected to Variable Light Speed?

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Discussion Overview

The discussion revolves around the concept of Doubly Special Relativity (DSR) and its potential connection to variable light speed. Participants explore the theoretical implications of DSR, including its historical context, invariant constants, and the nature of length and energy scales in different reference frames.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants express confusion about the purpose of the thread, questioning whether it is a complaint about the thread's title or a request for a summary of DSR.
  • One participant suggests that DSR posits an invariant Planck energy or Planck length alongside the invariant speed of light, raising the question of whether the Planck length is Lorentz-invariant.
  • Another participant asserts that all fundamental physical constants are invariant, but notes that the Planck and Boltzmann constants are not termed Lorentz invariants.
  • There is a discussion about the implications of DSR on the nature of length, with one participant questioning why a minimum length scale is proposed if it is already Lorentz invariant.
  • Some participants mention that the coordinate transformations in DSR need to be examined to understand the theory properly, referencing de Sitter Relativity as an example.
  • One participant introduces the idea that DSR is related to pseudo-differential operators, suggesting that this connection explains the variability of the speed of light.
  • A later reply requests a more specific reference regarding pseudo-differential operators in the context of DSR, indicating difficulty in finding relevant material.

Areas of Agreement / Disagreement

Participants express various viewpoints on the implications and interpretations of DSR, with no consensus reached on its connection to variable light speed or the nature of invariant constants. Disagreement exists regarding the clarity and relevance of certain concepts discussed.

Contextual Notes

Some statements made by participants depend on specific definitions and assumptions about invariance and reference frames, which remain unresolved in the discussion.

jjzeidner
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Hello. This is my first post on this site.

anyone here familiar with "Doubly Special Relativity"? an ARXIV paper was linked in the OP. Some follow up links or other advice would be appreciated.


thanks!
 
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why was this moved here and given an incorrect title?
 
jjzeidner said:
why was this moved here and given an incorrect title?
Because this is the proper forum for the topic. I have fixed the title.
 
the link I posted was FROM at page!
 
I know - my post was intended as a note to people who might read your post and be confused about what OP it was referencing, since your post is now an OP in its own thread and no longer a reply to the FAQ thread.
 
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I'm struggling with what this thread is trying to do. Is it a complaint that things were moved? Is it a request that somebody summarize the paper and explain DSR? Is there some specific question?
]

People seem to be upset, but the parth to making them un-upset does not seem clear to me.
 
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I think doubly SR is a thing from the past. There was a flurry of interest. It basically says that besides an invariant speed of light there is an invariant Planck-energy or Planck-length. Is the Planck length Lorentz-invariant?

The speed of light and the Planck constant are the same in every reference frame. Is G too?
 
A "yes" for a change ;).

All (fundamental) physical constants are 'invariant' as in observer independent. But the Planck’s constant or Boltzmann’s constant are not called 'Lorentz invariants'.

(In GR, of course G=c=1 so it would be really weird if it wasn't.)
 
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  • #10
Thelamon said:
A "yes" for a change ;).

All (fundamental) physical constants are 'invariant' as in observer independent. But the Planck’s constant or Boltzmann’s constant are not called 'Lorentz invariants'.

(In GR, of course G=c=1 so it would be really weird if it wasn't.)
But is G the same if measured in different frames?
 
  • #11
Thelamon said:
A "yes" for a change ;).

All (fundamental) physical constants are 'invariant' as in observer independent. But the Planck’s constant or Boltzmann’s constant are not called 'Lorentz invariants'.

(In GR, of course G=c=1 so it would be really weird if it wasn't.)
We can read:

"Doubly special relativity[1][2] (DSR) – also called deformed special relativity or, by some[who?], extra-special relativity – is a modified theory of special relativity in which there is not only an observer-independent maximum velocity (the speed of light), but also, an observer-independent maximum energy scale (the Planck energy) and/or a minimum length scale (the Planck length)."

Why say there is a minimum length scale, the Planck length, if it's Lorentz invariant already? Well the length itself changes for different observers. It goes to zero like all lengths. But DSR says this won't happen. Which is strange.
 
  • #12
BoraxZ said:
The speed of light and the Planck constant are the same in every reference frame. Is G too?
It's a little bit weird imo saying "the speed of light" (without c) and "the Planck constant" (without h) and then just G, so a little advice it's better to be complete and clear, specially if you're going to write an article once upon a time .. so Gravitational constant, G.
BoraxZ said:
But is G the same if measured in different frames?
Yes, measurements made which are not, are observer- or frame dependent.
BoraxZ said:
We can read
Yes, at least everyone reading this or anything else.
 
  • #13
BoraxZ said:
Why say there is a minimum length scale, the Planck length, if it's Lorentz invariant already? Well the length itself changes for different observers. It goes to zero like all lengths. But DSR says this won't happen. Which is strange.
The length constant doesn't shrink in that theory -- just as the value of ##c## doesn't change if you perform a Lorentz boost to a different velocity.

To understand this properly, one must look at the actual coordinate transformations proposed in the theory. Wikipedia quotes de Sitter Relativity as an example of DSR. Its length constant is indeed invariant.
 
  • #14
Doubly special relativity is related to pseudo-differential operators. This is why the speed of light is variable. The best place to learn about pseudo-differential operators is Rindler’s book ‘Relativity - special, general and cosmological’
 
  • #15
dx said:
Doubly special relativity is related to pseudo-differential operators. This is why the speed of light is variable. The best place to learn about pseudo-differential operators is Rindler’s book ‘Relativity - special, general and cosmological’
Please give a more specific reference. I cannot find the term "pseudo-differential" anywhere in that Rindler book. (I have the 2nd edition.)
 

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