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P versus NP and other resource-bounded computation.

0 votes
1 answer
113 views

Problems of similar complexity for different measures

It is a common belief that $\mathbf{P}\subsetneq\mathbf{PSPACE}$, thus (most likely) there are problems that are "harder" for time than for space. But is there a problem in $\mathbf{P}$ with a poly-sp …
David G's user avatar
  • 542
8 votes

Natural NP-complete problems with "large" witnesses

I came along some quite natural NP-complete problems that seemingly require long witnesses. The problems, parameterized by integers $C$ and $D$ are as follows: Input: A one-tape TM $M$ Question: Is t …
David G's user avatar
  • 542
6 votes

Equivalent definitions of time constructibility

In the last few days I thought a lot about (fully) time-constructible functions and I will present what I found out by answering Q1 and Q3. Q2 seems too hard. Q3: Kobayashi in his article (the refer …
David G's user avatar
  • 542
14 votes
1 answer
1k views

Equivalent definitions of time constructibility

We say that a function $f:\mathbb{N}\rightarrow\mathbb{N}$ is time-constructible, if there exists a deterministic multi-tape Turing machine $M$ that on all inputs of length $n$ makes at most $f(n)$ st …
David G's user avatar
  • 542
5 votes
0 answers
188 views

Real-time countable vs fully time-constructible

Real-time countable functions were used in time hierarchy theorem in the papers of Hartmanis and Stearns (Theorem 9, 9.1 ...) and also of Hennie and Stearns (Theorems 3, 5, 7 ...). Now it is a "standa …
David G's user avatar
  • 542
3 votes

An explicit separation between time-constructibility and space-constructibility?

If all space-constructible functions are time-constructible, then $EXP-TIME=EXP-SPACE$. To prove that (and to give an example of a non-trivial space-constructible but presumably not time-constructible …
David G's user avatar
  • 542