I read this story a long time ago. I am unsure if it was a short, a novella or a full novel, but given my so-little memory of it, I believe it was probably a short.
On to the plot points I remember:
- someone discovered how to harness the power of rotation
- you got the power, but whatever you harvested the energy from started slowing down, until eventually it stopped rotating
- this was used/abused by far too many people, causing the Earth to stop spinning and then the Moon, and they were starting in on the Solar System when the story started (IIRC)
- someone realized that they could have godlike amounts of power by harnessing the rotational energy of the entire universe
- somehow they used the massive energy to create copies of themselves (in time??)
- the two main characters were trying to kill each other, but were in a stalemate as with the unlimited energy they had they could make an almost infinite number of copies of themselves