SEPARATING NONDETERMINISTIC TIME COMPLEXITY CLASSES

A recurslve padding technique is used to obtain conditions sufficient for separation of nondetermlmsttc multltape Turlng machine time complexity classes If T2 is a running time and Tl(n + 1) grows more dslowly than To(n), then there is a language which can be accepted nondetermmlstlcally within time bound To but which cannot be accepted nondetermlnlStlcally within time bound T1. If even To(n + f(n)) grows more slowly than Tz(n), where f is the very slowly growing “rounded reverse” of some real-time countable function, then there is such a language over a single-letter alphabet. The strongest known dmgonalization results for both deterministic and nondetermlmstlc time complexity classes are reviewed and orgamzed for comparison with the results of the new padding technique. © 1978, ACM. All rights reserved.