There's hard science fiction and then there's Greg Egan. This Australian science fiction author and computer programmer is justly celebrated for his incredibly imaginative and rigorous extrapolations of cutting edge math and physics. Science fiction just doesn't get much "harder" than Egan's stuff.
Permutation City is one of Egan's early novels and one of my favorites. Here's the description:
Far out man! But Egan pulls it off and the Kindle edition can be had for the low, low price of $2.99.Paul Durham keeps making Copies of himself: software simulations of his own brain and body which can be run in virtual reality, albeit seventeen times more slowly than real time. He wants them to be his guinea pigs for a set of experiments about the nature of artificial intelligence, time, and causality, but they keep changing their mind and bailing out on him, shutting themselves down.
Maria Deluca is an Autoverse addict; she's unemployed and running out of money, but she can't stop wasting her time playing around with the cellular automaton known as the Autoverse, a virtual world that follows a simple set of mathematical rules as its “laws of physics”.
Paul makes Maria a very strange offer: he asks her to design a seed for an entire virtual biosphere able to exist inside the Autoverse, modelled right down to the molecular level. The job will pay well, and will allow her to indulge her obsession. There has to be a catch, though, because such a seed would be useless without a simulation of the Autoverse large enough to allow the resulting biosphere to grow and flourish — a feat far beyond the capacity of all the computers in the world.
And he just keeps coming up with amazing ideas. Here's the idea behind his Orthogonal trilogy published 2011-2013.:
Other great stuff includes novels Diaspora, Quarantine, Distress and Schild's Ladder, as well as any of his collections of short stories (Axiomatic is particularly good).Orthogonal is a science fiction trilogy by Australian author Greg Egan taking place in a universe where, rather than three dimensions of space and one of time, there are four fundamentally identical dimensions. While the characters in the novels always perceive three of the dimensions as space and one as time, this classification depends entirely on their state of motion, and the dimension that one observer considers to be time can be seen as a purely spatial dimension by another observer.The plot involves the inhabitants of a planet that comes under threat from a barrage of high-velocity meteors known as 'hurtlers', who launch a generation ship that exploits the distinctive relativistic effects present in this universe which allow far more time to elapse on the ship than passes on the home world, in order for the ship's inhabitants to develop the technology needed to protect the planet. The three novels deal with a succession of increasingly advanced scientific discoveries, as well as a number of radical social changes in the culture of the generation ship's passengers.
If reading Egan doesn't blow your mind, you just aren't paying attention!