My question is about the apparent CPT violation of the observed universe, due to the imbalance of matter and antimatter, but first I have a motivating observation:

General relativity respects time reversal (T) symmetry. However, formation of black holes ostensibly spoil T symmetry, because a black hole cannot un-form. What preserves T symmetry in this case is that if you evolve the system which formed the black hole backwards in time, you get a white hole singularity, which is the time-reversal of the black hole. (We usually don't think about white holes because they aren't observed, presumably due to initial conditions of the universe.)

Now I wonder if something analogous can fix the observed CPT asymmetry: Is there a reasonable way in which antimatter could come to dominate at the end of the universe, as a CPT analog of the matter domination of the current "early" phase of the universe?

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    $\begingroup$ A symmetric theory can have spontaneously broken non-symmetric solutions. General relativity isn't particularly special in that respect and one does not have to be desperate about finding non-physical solutions that keep thinks symmetric looking. Time reversal invariance is simply not the normal state of nature. Humpty Dumpty, once broken, will stay broken. $\endgroup$ – CuriousOne Apr 1 '16 at 0:46

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