Greg Egan is definitely in the list of authors with the most radically hard science fiction ideas, even more extravagant than those I found in Alfred Bester books.

Speaking of the Dust Theory, this looks very close to concept as Max Tegmark's Mathematical universe hypothesis: https://en.wikipedia.org/wiki/Mathematical_universe_hypothes...

Tegmark's book goes over it in a very readable way: https://www.amazon.de/Our-Mathematical-Universe-Ultimate-Rea...