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After reading this article regarding Positronium BEC formation (for lasing purposes), there is a mention in there regarding Ps "up" atoms not annihilating with "down" atoms, the article is pretty vague about it and does not give much details, but i presume it is referring to the +1 and -1 polarizations of orthopositronium (J=1) excitation in a magnetic field.

Is there a known reference for the exact annihilation rates/cross sections/etc for Ps of the same type? certainly if one could put a condensate of positroniums of the same type and not having them annihilate each other at all or a very low rate, it would be a big deal for the future of space propulsion

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Not an answer, just a hint, but this is a bose-to-bose system, namely positronium effective field to photon field, so it is just a classical problem with effective parameters. I don't know an estimate for the parameters, hence not an answer. – Ron Maimon Sep 14 '12 at 2:44

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