How does Horava Lifshitz gravity affect the speed of light in bounce solutions?

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Discussion Overview

The discussion revolves around the implications of Horava-Lifshitz gravity on the speed of light, particularly in the context of bounce solutions in cosmology. Participants explore the theoretical underpinnings and consequences of these models, questioning the nature of time and causality in scenarios where traditional measurements may not apply.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant notes that according to a Wikipedia entry, the speed of light may reach infinite values at high energies in Horava-Lifshitz gravity, raising questions about its behavior during bounce solutions.
  • Another participant emphasizes the necessity of defining standard units and principles for measuring physical quantities, suggesting that the speed of light could be treated as a constant in a specific framework.
  • A participant questions the implications of the absence of physical clocks surviving the bounce, challenging the notion of time before and after the bounce.
  • There is a suggestion that the lack of surviving clocks complicates the understanding of causality in the context of bounce cosmology.
  • One participant inquires whether bounce solutions are a natural consequence of Horava-Lifshitz gravity, indicating a need for clarity on this point.
  • A later reply references a paper discussing the relationship between Horava gravity and bouncing cosmologies, but also notes that this relationship is not guaranteed.

Areas of Agreement / Disagreement

Participants express differing views on the implications of Horava-Lifshitz gravity for the speed of light and the nature of bounce solutions. There is no consensus on whether bounce solutions are a definitive outcome of the theory or how to interpret the implications for time and causality.

Contextual Notes

Participants highlight the importance of defining fundamental concepts and measurements, indicating that assumptions about the survival of physical clocks and the nature of time may significantly affect interpretations of bounce solutions in Horava-Lifshitz cosmology.

palmer eldtrich
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According to the wikipedia page on Horava Lifshitz gravity , the value of c
"Also, the speed of light has an infinite value at high energies."
This seems very interesting. In Horava cosmology its common to see bounce solutions, so what happens to the speed of light as one is on the other side of the bounce? Doe sit go infinite at the bounce and then back to finite?
Also I note that the well known BGV theroem for a past finite universe by Borde Guth Vielnkin, they seem to base their argument based on the idea that in a finite time a hypothetical observer reaches c. If Horava gravity is used then assuming wiki has it right, then this theorem should be violated. Is that right?
 
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Hi Palmer, you have to define what you want to use as standard units by which you can measure other objects by, and the fundamental principles by which to extrapolate those measurements across the universe.

If you define the speed of light in vacuo as a constant c, a property of space-time itself, then you only need to define a standard clock (say) and the rest (length and mass and energy) will follow. In QM you could define Planck's constant, and Planck units as fundamental.

The question about what happens to the speed of light through the 'bounce' will be a question of what changes or survives through the bounce, certainly no physical clocks!

Garth
 
so if no physical clocks surivie in what sense is i it before?
 
You have to define something else that survives the bounce in order to know what you are talking about, I suspect that is the problem with many theories of the 'origin' or 'pre-origin' of the universe!

Garth
 
is the bounce a natural consequence of Horava Lifshitz gravity?
 
Hi Garth, thansk for your replies. I am afraid I dint quite understand your last one.It was a mention of a paper that says Horava leads to bouncing cosmologies, but then you said Horava doesn always lead to bouncing cosmology.
Do you mind if I pick up on, if a clock doesn't survive , how is there still a notion of cause ad effect?
 

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