Causation is not a useful concept when we’re talking about the fundamental level of nature, precisely because all fundamental interactions (with some very obscure exceptions) are completely time-symmetric.
Assuming CPT symmetry, the very reason why there’s still matter in the universe (as opposed to it all having annihilated with antimatter) in the first place must be one of those very obscure exceptions.
It’s true that CP-violations appear to be a necessary condition for the baryon asymmetry (if you make certain natural-seeming assumptions). It’s another question whether the observed CP-violations are sufficient for the asymmetry, if the other Sakharov conditions are met. And one of the open problems in contemporary cosmology is precisely that they don’t appear to be sufficient, that the subtle CP-violations we have observed so far (only in four types of mesons) are too subtle to account for the huge asymmetry between matter and anti-matter. They would only account for a tiny amount of that asymmetry. So, yeah, the actual violations of T-symmetry we see are in fact obscure exceptions. They are not sufficient to account for either the pervasive time asymmetry of macroscopic phenomena or the pervasive baryon asymmetry at the microscopic level. There are two ways to go from here: either there must be much more significant CP-violations that we haven’t yet been able to observe, or the whole Sakharov approach of accounting for the baryon asymmetry dynamically is wrong, and we have to turn to another kind of explanation (anthropic, maybe?). The latter option is what we have settled on when it comes to time asymmetry—we have realized that a fundamental single-universe dynamical explanation for the Second Law is not on the cards—and it may well turn out to be the right option for the baryon asymmetry as well.
It’s also worth noting that CP-violations by themselves would be insufficient to account for the asymmetry, even if they were less obscure than they appear to be. You also need the Second Law of Thermodynamics (this is the third Sakharov condition). In thermodynamic equilibrium any imbalance between matter and anti-matter generated by CP-violating interactions would be undone.
In any case, even if it turns out that CP-violating interactions are plentiful enough to account for the baryon asymmetry, they still could not possibly account for macroscopic temporal asymmetry. The particular sort of temporal asymmetry we see in the macroscopic world involves the disappearance of macroscopically available information. Microscopic CP-violations are information-preserving (they are CPT symmetric), so they cannot account for this type of asymmetry. If there is going to be a fundamental explanation for the arrow of time it would have to involve laws that don’t preserve information. The only serious candidate for this so far is (real, not instrumental) wavefunction collapse, and we all know how that theory is regarded around these parts.
Assuming CPT symmetry, the very reason why there’s still matter in the universe (as opposed to it all having annihilated with antimatter) in the first place must be one of those very obscure exceptions.
It’s true that CP-violations appear to be a necessary condition for the baryon asymmetry (if you make certain natural-seeming assumptions). It’s another question whether the observed CP-violations are sufficient for the asymmetry, if the other Sakharov conditions are met. And one of the open problems in contemporary cosmology is precisely that they don’t appear to be sufficient, that the subtle CP-violations we have observed so far (only in four types of mesons) are too subtle to account for the huge asymmetry between matter and anti-matter. They would only account for a tiny amount of that asymmetry. So, yeah, the actual violations of T-symmetry we see are in fact obscure exceptions. They are not sufficient to account for either the pervasive time asymmetry of macroscopic phenomena or the pervasive baryon asymmetry at the microscopic level. There are two ways to go from here: either there must be much more significant CP-violations that we haven’t yet been able to observe, or the whole Sakharov approach of accounting for the baryon asymmetry dynamically is wrong, and we have to turn to another kind of explanation (anthropic, maybe?). The latter option is what we have settled on when it comes to time asymmetry—we have realized that a fundamental single-universe dynamical explanation for the Second Law is not on the cards—and it may well turn out to be the right option for the baryon asymmetry as well.
It’s also worth noting that CP-violations by themselves would be insufficient to account for the asymmetry, even if they were less obscure than they appear to be. You also need the Second Law of Thermodynamics (this is the third Sakharov condition). In thermodynamic equilibrium any imbalance between matter and anti-matter generated by CP-violating interactions would be undone.
In any case, even if it turns out that CP-violating interactions are plentiful enough to account for the baryon asymmetry, they still could not possibly account for macroscopic temporal asymmetry. The particular sort of temporal asymmetry we see in the macroscopic world involves the disappearance of macroscopically available information. Microscopic CP-violations are information-preserving (they are CPT symmetric), so they cannot account for this type of asymmetry. If there is going to be a fundamental explanation for the arrow of time it would have to involve laws that don’t preserve information. The only serious candidate for this so far is (real, not instrumental) wavefunction collapse, and we all know how that theory is regarded around these parts.