Space bounded computations : Review and new separation results

  • J. Hartmanis
  • Desh Ranjan
Invited Lectures
Part of the Lecture Notes in Computer Science book series (LNCS, volume 379)


In this paper we review the key results about space bounded complexity classes, discuss the central open problems and outline the relevant proof techniques. We show that, for a slightly modified Turing machine model, the low level deterministic and nondeterministic space bounded complexity classes are different. Furthermore, for this computation model, we show that Savitch and Immerman-Szelepcsényi theorems do not hold in the range lg lg n to lg n. We also discuss some other computation models to bring out and clarify the importance of space constructibility and establish some results about these models. We conclude by enumerating a few open problems which arise out of the discussion.


Turing Machine Input Tape Deterministic Turing Machine Nondeterministic Turing Machine Work Tape 
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Copyright information

© Springer-Verlag Berlin Heidelberg 1989

Authors and Affiliations

  • J. Hartmanis
    • 1
  • Desh Ranjan
    • 1
  1. 1.Computer Science DepartmentCornell UniversityUSA

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