If you have a universe of a certain complexity, then to simulate another universe of equal complexity it would have to be that universe to fully simulate it. To simulate a universe, you have to be sufficiently more complex and have sufficiently more expendable energy.
If you have a universe of a certain complexity, then to simulate another universe of equal complexity it would have to be that universe to fully simulate it. To simulate a universe, you have to be sufficiently more complex and have sufficiently more expendable energy.