# Open problem of classical representation of neutral antimatter bodies?

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 P: 2 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.
 Homework Sci Advisor HW Helper Thanks P: 12,739 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.
 Mentor P: 11,815 Relativity does not care about matter <-> antimatter. It would be exactly like a neutral body made out of matter.
P: 2
Open problem of classical representation of neutral antimatter bodies?

 Quote by Simon Bridge 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.
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.
Mentor
P: 11,815
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.

 I raise the question because I have seen on various websites the treatment of a matter-anti-matter gravitational repulsion.
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.
 Homework Sci Advisor HW Helper Thanks P: 12,739 It's the way to bet isn't it? OP is probably thinking about stuff like: http://en.wikipedia.org/wiki/Gravita..._of_antimatter http://www.phy.duke.edu/~phillips/gr...rameIndex.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.
 Mentor P: 16,316 The OP isn't thinking of stuff like that, and as the OP won't be back, there's not much point in continuing trying to answer his questions.

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