Alternating space is closed under complement and other simulations for sublogarithmic space

(c) ASPACE(s(n))=CO-ASPACE(s(n)), i.e., the alternating space is closed under complement, independently of whether s(n) is above log⁡n and of whether the original machine can get into an infinite loop. This solves a long-standing open problem. Quite surprisingly, this complementary simulation does not eliminate infinite loops-the new machine itself goes to infinite loops along some computation paths.