# Open problem of classical representation of neutral antimatter bodies?

1. Feb 12, 2013

### Collider

Can anybody please tell me how to represent a neutral antimatter body such as a planet or a star in the classical formulation of special and general relativities?

Thanks.

2. Feb 13, 2013

### Simon Bridge

Re: Open problem of classical representation of neutral antimatter bod

Welcome to PF;
What do you mean by "represent a ... body"?
eg. can you show me how you would represent a regular matter body in SR and GR?

iirc: SR is about relative motion, and GR is about gravity - in a nutshell.

3. Feb 13, 2013

### Staff: Mentor

Re: Open problem of classical representation of neutral antimatter bod

Relativity does not care about matter <-> antimatter. It would be exactly like a neutral body made out of matter.

4. Feb 14, 2013

### Collider

Re: Open problem of classical representation of neutral antimatter bod

Newton's equation, Galileo's Relativity, and Einstein's relativities deal with a body constituted by matter with a given mass m.

The only classical conjugation into anti-matter that I know of is the sign of the charge but I am interested in Newton's equation of motion or Einstein gravitation of a neutral anti-matter body that has no charge.

Does this make the entire 20th century of science inapplicable for a classical representation of neutral anti-matter?

I raise the question because I have seen on various websites the treatment of a matter-anti-matter gravitational repulsion. I have trouble accepting them unless I see a classical representation of the gravitational field of a neutral antimatter astrophysical body.

5. Feb 14, 2013

### Staff: Mentor

Re: Open problem of classical representation of neutral antimatter bod

Charge is just one of the quantum numbers which are inverted for antimatter, there are more. But it does not matter: relativity cares about the energy density only, and that is the same both for matter and antimatter.
See my previous post: It would be exactly like a neutral body made out of matter.

It is expected that antimatter and matter attract each other, and anything else would be a huge surprise. It would require serious modifications to relativity, and allow a violation of energy conservation and similar things.

6. Feb 15, 2013

### Simon Bridge

Re: Open problem of classical representation of neutral antimatter bod

It's the way to bet isn't it?

OP is probably thinking about stuff like:
http://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter
http://www.phy.duke.edu/~phillips/gravity/frameIndex.html

National Geographic ran a pop-sci article in Feb 2012 titled: Is Dark Energy Really "Repulsive Gravity"? citing and quoting Massimo Villata, "an astrophysicist at the Observatory of Turin in Italy".

Investigating that last one turns up stuff like:
Villata M. (2012) "Dark energy" in the Local Void... a "letter to the editor" in Astrophysics and Space Science, which is cited by
by Hajdukovic D. S. (2013) Can observations inside the Solar System reveal the gravitational properties of the quantum vacuum?, Astrophysics and Space Science, February 2013, Volume 343, Issue 2, pp 505-509
... who propose a test.

afaik, there is no special reason to suspect antimatter has anti-gravity except perhaps that the prefix "anti" appears in both the names.

7. Feb 15, 2013