The Complexity of Finding SUBSEQ(A)
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by
Stephen Fenner
,
William Gasarch
,
Brian Postow
| Citations: | 1 - 0 self |
BibTeX
@MISC{Fenner_thecomplexity,
author = {Stephen Fenner and William Gasarch and Brian Postow},
title = {The Complexity of Finding SUBSEQ(A)},
year = {}
}
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Abstract
Higman showed that if A is any language then SUBSEQ(A) is regular. His proof was nonconstructive. We show that the result cannot be made constructive. In particular we show that if f takes as input an index e of a total Turing Machine Me, and outputs a DFA for SUBSEQ(L(Me)), then ∅ ′ ′ ≤T f (f is Σ2-hard). We also study the complexity of going from A to SUBSEQ(A) for several representations of A and SUBSEQ(A).
