É " Crystal Nights ", de Greg Egan.
“You created this world?” Primo asked him.
“Yes.”
“You shaped our history?”
“In part,” Daniel said. “Many things have been down to chance, or to your own choices.”
“Did you stop us having children?” Primo demanded.
“Yes,” Daniel admitted.
“Why?”
“There is no room left in the computer. It was either that, or many more deaths.”