Hal Finney wrote:
I imagine that multiple universes could exist, a la Schmidhuber's ensemble or Tegmark's level 4 multiverse. Time does not play a special role in the descriptions of these universes.
Doesn't Schmidhuber consider only universes that are the results of computations? Can't we consider any computation as having an intrinsic "causal structure"? How would it be possible to write an algorithm that describes a "Life" universe where there's no time, where the t-axis is replaced by a z-axis, for example?
Tegmark in one of his papers considers universes with two or more time dimensions.
If this universe is computable, it can be simulated by an algorithm that can run in a universe with only one time dimension. Perhaps the algorithm would go back and forth between simulating time increments in different directions, like how a regular computer can simulate a parallel computer.