The method of forced enumeration for nondeterministic automata
Acta Informatica
Nondeterministic space is closed under complementation
SIAM Journal on Computing
Space bounded computations: review and new separation results
MFCS '89 Selected papers of the symposium on Mathematical foundations of computer science
Nondeterministic computations in sublogarithmic space and space constructibility
SIAM Journal on Computing
Tally versions of the Savitch and Immerman-Szelepcse´nyi theorems for sublogarithmic space
SIAM Journal on Computing
The alternation hierarchy for sublogarithmic space is infinite
Computational Complexity
The Sublogarithmic Alternating Space World
SIAM Journal on Computing
Some Results on Tape-Bounded Turing Machines
Journal of the ACM (JACM)
A Note Concerning Nondeterministic Tape Complexities
Journal of the ACM (JACM)
Separating Nondeterministic Time Complexity Classes
Journal of the ACM (JACM)
Turing Machines with Sublogarithmic Space
Turing Machines with Sublogarithmic Space
Bridging Across the log(n) Space Frontier
MFCS '95 Proceedings of the 20th International Symposium on Mathematical Foundations of Computer Science
Strong Optimal Lower Bounds for Turing Machines that Accept Nonregular Languages
MFCS '95 Proceedings of the 20th International Symposium on Mathematical Foundations of Computer Science
Magic numbers in the state hierarchy of finite automata
Information and Computation
Theoretical Computer Science
Passively mobile communicating machines that use restricted space
FOMC '11 Proceedings of the 7th ACM ACM SIGACT/SIGMOBILE International Workshop on Foundations of Mobile Computing
Passively mobile communicating machines that use restricted space
Theoretical Computer Science
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We show that, for an arbitrary function h(n) and each recursive function l(n), that are separated by a nondeterministically fully space constructible g(n), such that h(n)∈Ω(g(n)) but l(n) ∈ Ω(g(n)), there exists a unary language L in NSPACE(h(n)) that is not contained in NSPACE(l(n)). The same holds for the deterministic case.The main contribution to the well-known Space Hierarchy Theorem is that (i) the language L separating the two space classes is unary (tally), (ii) the hierarchy is independent of whether h(n) or l(n) are in Ω(log n) or in o(log n), (iii) the functions h(n) or l(n) themselves need not be space constructible nor monotone increasing, (iv) the hierarchy is established both for strong and weak space complexity classes. This allows us to present unary languages in such complexity classes as, for example, NSPACE(log log n . log*n)\ NSPACE(log log n), using a plain diagonalization.