Mathematical systems theory

, Volume 24, Issue 1, pp 41–52 | Cite as

On problems for which no oracle can help

  • Juraj Hromkovič


It is shown that for some languages no oracle (or only oracles with exponential density—depending on the way in which the space complexity in oracle computations is measured) can help to decrease their time-space complexity. This result is shown to be to some extent independent of the machine model used (single-tape, multitape, or multihead Turing machines, RAMs, etc.)

Further, a new complexity measure reflecting the amount of information provided by an oracle for language recognition is introduced. The tradeoff of this measure and time-space complexity is discussed.


Computational Mathematic Space Complexity Turing Machine Complexity Measure Machine Model 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag New York Inc. 1991

Authors and Affiliations

  • Juraj Hromkovič
    • 1
  1. 1.Department of Theoretical CyberneticsComenius UniversityBratislavaCzechoslovakia

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