# Horava Lifshitz gravity and c

1. Mar 12, 2015

### palmer eldtrich

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?

2. Mar 12, 2015

### Garth

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

3. Mar 12, 2015

### palmer eldtrich

so if no physical clocks surivie in what sense is i it before?

4. Mar 12, 2015

### Garth

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

5. Mar 12, 2015

### palmer eldtrich

is the bounce a natural consequence of Horava Lifshitz gravity?

6. Mar 12, 2015

### Garth

7. Mar 13, 2015

### palmer eldtrich

Hi Garth, thansk for your replies. Im 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 doesnt survive , how is there still a notion of cause ad effect?