# Sakurai: gravitational repulsion

1. Jul 13, 2011

### Manojg

Hi,

I was reading Sakurai's "Invariance Principles and Elementary particles". In first chapter, second paragraph (page 3), there is a line "The analogous dimensionless constant that characterizes the gravitational repulsion between two protons is .......".

Any body likes to comment on this, why there is gravitational repulsion or this is just a typo.

Thanks,

Last edited: Jul 13, 2011
2. Jul 13, 2011

### Manojg

Any body home?

3. Jul 13, 2011

### Staff: Mentor

I'm not sure this helps, but I found this under Gravitational Coupling Constant on wikipedia:

Looks like it is talking about the repulsion from the electric charge, not gravity. But I haven't read Sakurai's book, so I don't really know.

4. Jul 13, 2011

### bcrowell

Staff Emeritus
Sounds like a typo to me. Maybe if you quoted more context, we'd be able to tell better.

5. Jul 13, 2011

### Creator

Hilbert describes a gravitational repulsion which is velocity dependent, IOWs, the gravitational interaction changes at relativistic (coordinate) velocities, reaching a repulsion at a critical velocity of c/ sq.rt(2)....
http://arxiv.org/PS_cache/arxiv/pdf/0904/0904.1578v1.pdf

So this seems like a reference to an application of Hilbert gravitational repulsion to sub-atomic particles which includes their charge.

Creator

6. Jul 13, 2011

### bcrowell

Staff Emeritus
Loinger is a kook. The paper you linked to was not published in a peer-reviewed journal. Please review PF rules https://www.physicsforums.com/showthread.php?t=414380 , which state: "It is against our Posting Guidelines to discuss, in the PF forums or in blogs, new or non-mainstream theories or ideas that have not been published in professional peer-reviewed journals or are not part of current professional mainstream scientific discussion."

In any case, the repulsion would not occur in the case of two protons.

7. Jul 14, 2011

### Manojg

Here are more lines:

"The various classes of fundamental interactions are characterized by coupling constants that differ in many orders of magnitude. The electromagnetic coupling is characterized by the well-known dimensionless constant 1/137. The analogous dimensionless constant that characterizes the gravitational repulsion between two protons is $G^{2}_{grav} M^{2}_{p}/\hbar c = 2 \times 10^{-39}$, which shows that we can essentially ignore gravity in discussing elementary particle phenomena.

8. Jul 14, 2011

### bcrowell

Staff Emeritus
OK, this is clearly just a typo. Instead of "gravitational repulsion," it should say "gravitational attraction."

9. Jul 14, 2011

Thanks.