"There is a limit to the amount of computation that can be done by a given amount of matter that only new physics could change. Given that limit, at best you would need every particle in our universe just to simulate an identical one. It's more likely that the best possible simulation would have significantly reduced fidelity and/or size with respect to its host universe, thus the inevitability component of the simulation argument falls apart."
Or, potentially, one would only need to simulate the minds of any observesers in the simulation, not every particle in the simulated universe.
Or, potentially, one would only need to simulate the minds of any observesers in the simulation, not every particle in the simulated universe.
...for every possible interaction those minds could have with the simulated universe. The only lossless way to simulate a mind's interaction with a universe is to simulate the universe. Further, one must define "observer", as well as simulate accurately what happens to non-"observer" objects, animals, microbes, etc. while "observers" aren't looking.
Or, potentially, one would only need to simulate the minds of any observesers in the simulation, not every particle in the simulated universe.