If A simulates the universe, it sees that its outputs appear on W2 without postulating anything beyond physical law.
Usually you can’t simulate the whole universe up to the current time from inside that universe—even if you know the laws and initial conditions—because you run out of storage space. With a growing universe, there may be some possibility of completely simulating its early stages...
Again, neither can I, but I still have beliefs about what the shortest description of the universe is. In particular, I don’t believe that my actions figure into the shortest model of the world in a special way, although there is some uncertainty about whether I am only able to hold this belief because I am more introspective than AIXI.
Usually you can’t simulate the whole universe up to the current time from inside that universe—even if you know the laws and initial conditions—because you run out of storage space. With a growing universe, there may be some possibility of completely simulating its early stages...
Again, neither can I, but I still have beliefs about what the shortest description of the universe is. In particular, I don’t believe that my actions figure into the shortest model of the world in a special way, although there is some uncertainty about whether I am only able to hold this belief because I am more introspective than AIXI.