Space Hierarchy Theorem Revised

  • Authors:

  • Viliam Geffert

  • Affiliations:

  • -

  • Venue:
  • MFCS '01 Proceedings of the 26th International Symposium on Mathematical Foundations of Computer Science
  • Year:
  • 2001

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Abstract

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)) - 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. This allows us, using diagonalization, to present unary languages in such complexity classes as, for example, NSPACE(log log nċlog*n) - NSPACE(log log n).