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Is there any difference between matter and antimatter other than the charge? Could we (theoretically of course) find in space a civilization made of antimatter?

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The operator $C$ replaces every particle with its antiparticle. If $C$ is a symmetry of the universe, then there is no difference between matter and antimatter. However $C$ is not a symmetry. This can be seen in that all neutrinos are left-handed, but antineutrinos are right-handed. There is also evidence that kaons and antikaons have different rates of decay. This suggests that $CP$, which includes also a mirror transformation, is a candidate symmetry. Experiments show that $CP$ is not an exact symmetry, but the violation is very small. So an antimatter star or galaxy is not ruled out.

If you can convincingly explain why we don't see any antimatter galaxies, you would have good reason to plan a trip to Stockholm.

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  • $\begingroup$ I have seen somewhere, perhaps it was on wikipedia, that CPT is an exact symmetry. Is this true? $\endgroup$
    – PhotonBoom
    Apr 10 '14 at 13:22
  • $\begingroup$ Yes, one of the most important results of quantum field theory is the CPT theorem, which says that CPT is an exact symmetry of any reasonable QFT. $\endgroup$ Apr 10 '14 at 15:45
  • $\begingroup$ Ah nice to know, last question about it: Any idea how well tested this symmetry is? $\endgroup$
    – PhotonBoom
    Apr 10 '14 at 15:53
  • $\begingroup$ @PhotonicBoom A recent conference on searches for CPT and Lorentz symmetry violation $\endgroup$
    – rob
    May 12 '14 at 23:05

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