A truely morphic characterization of recursively enumerable sets

2006 ◽  
pp. 205-213 ◽  
Author(s):  
Franz Josef Brandenburg
Keyword(s):  
Recursively Enumerable ◽  
Recursively Enumerable Sets

Characterization of recursively enumerable sets

1972 ◽  
Vol 37 (3) ◽  
pp. 507-511 ◽  
Author(s):  
Jesse B. Wright
Keyword(s):  
Transitive Closure ◽  
Successor Function ◽  
Function Composition ◽  
Recursive Functions ◽  
Recursively Enumerable ◽  
Abstract Setting ◽  
Recursively Enumerable Sets ◽  
Bracket Operation

AbstractLet N, O and S denote the set of nonnegative integers, the graph of the constant 0 function and the graph of the successor function respectively. For sets P, Q, R ⊆ N2 operations of transposition, composition, and bracketing are defined as follows: P∪ = {〈x, y〉 ∣ 〈y, x〉 ∈ P}, PQ = {〈x, z〉 ∣ ∃y〈x, y〉 ∈ P & 〈y, z〉 ∈ Q}, and [P, Q, R] = ⋃n ∈ M(Pn Q Rn).Theorem. The class of recursively enumerable subsets of N2 is the smallest class of sets with O and S as members and closed under transposition, composition, and bracketing.This result is derived from a characterization by Julia Robinson of the class of general recursive functions of one variable in terms of function composition and “definition by general recursion.” A key step in the proof is to show that if a function F is defined by general recursion from functions A, M, P and R then F = [P∪, A∪M, R].The above definitions of the transposition, composition, and bracketing operations on subsets of N2 can be generalized to subsets of X2 for an arbitrary set X. In this abstract setting it is possible to show that the bracket operation can be defined in terms of K, L, transposition, composition, intersection, and reflexive transitive closure where K: X → X and L: X → X are functions for decoding pairs.

Simplicity of recursively enumerable sets

1967 ◽  
Vol 32 (2) ◽  
pp. 162-172 ◽  
Author(s):  
Robert W. Robinson
Keyword(s):  
Recursively Enumerable ◽  
Original Definition ◽  
Recursively Enumerable Sets ◽  
Simple Sets

In §1 is given a characterization of strongly hypersimple sets in terms of weak arrays which is in appearance more restrictive than the original definition. §1 also includes a new characterization of hyperhypersimple sets. This one is interesting because in §2 a characterization of dense simple sets is shown which is identical in all but the use of strong arrays instead of weak arrays. Another characterization of hyperhypersimple sets, in terms of descending sequences of sets, is given in §3. Also a theorem showing strongly contrasting behavior for simple sets is presented. In §4 a r-maximal set which is not contained in any maximal set is constructed.

Decidability of the two-quantifier theory of the recursively enumerable weak truth-table degrees and other distributive upper semi-lattices

1996 ◽  
Vol 61 (3) ◽  
pp. 880-905 ◽  
Author(s):  
Klaus Ambos-Spies ◽  
Peter A. Fejer ◽  
Steffen Lempp ◽  
Manuel Lerman
Keyword(s):  
Decision Procedure ◽  
Finite Lattice ◽  
Truth Table ◽  
Recursively Enumerable ◽  
Finite Lattices ◽  
Recursively Enumerable Sets ◽  
Weak Truth Table Degrees ◽  
Quantifier Theory ◽  
The Ideal

AbstractWe give a decision procedure for the ∀∃-theory of the weak truth-table (wtt) degrees of the recursively enumerable sets. The key to this decision procedure is a characterization of the finite lattices which can be embedded into the r.e.wtt-degrees by a map which preserves the least and greatest elements: a finite lattice has such an embedding if and only if it is distributive and the ideal generated by its cappable elements and the filter generated by its cuppable elements are disjoint.We formulate general criteria that allow one to conclude that a distributive upper semi-lattice has a decidable two-quantifier theory. These criteria are applied not only to the weak truth-table degrees of the recursively enumerable sets but also to various substructures of the polynomial many-one (pm) degrees of the recursive sets. These applications to thepmdegrees require no new complexity-theoretic results. The fact that thepm-degrees of the recursive sets have a decidable two-quantifier theory answers a question raised by Shore and Slaman in [21].

On degrees of unsolvability and complexity properties

1975 ◽  
Vol 40 (4) ◽  
pp. 529-540 ◽  
Author(s):  
Ivan Marques
Keyword(s):  
Turing Degree ◽  
Recursively Enumerable ◽  
Recursively Enumerable Sets ◽  
Complete Sets ◽  
Turing Complete ◽  
Degrees Of Unsolvability

In this paper we present two theorems concerning relationships between degrees of unsolvability of recursively enumerable sets and their complexity properties.The first theorem asserts that there are nonspeedable recursively enumerable sets in every recursively enumerable Turing degree. This theorem disproves the conjecture that all Turing complete sets are speedable, which arose from the fact that a rather inclusive subclass of the Turing complete sets, namely, the subcreative sets, consists solely of effectively speedable sets [2]. Furthermore, the natural construction to produce a nonspeedable set seems to lower the degree of the resulting set.The second theorem says that every speedable set has jump strictly above the jump of the recursive sets. This theorem is an expected one in view of the fact that all sets which are known to be speedable jump to the double jump of the recursive sets [4].After this paper was written, R. Soare [8] found a very useful characterization of the speedable sets which greatly facilitated the proofs of the results presented here. In addition his characterization implies that an r.e. degree a contains a speed-able set iff a′ > 0′.

Some Characterization of Recursively Enumerable Sets

2002 ◽  
Vol 79 (2) ◽  
pp. 157-163
Author(s):  
Wit Foryś
Keyword(s):  
Recursively Enumerable ◽  
Recursively Enumerable Sets

A Purely Homomorphic Characterization of Recursively Enumerable Sets

1979 ◽  
Vol 26 (2) ◽  
pp. 345-350 ◽  
Author(s):  
K. Culik
Keyword(s):  
Recursively Enumerable ◽  
Recursively Enumerable Sets

On the Characterization of Recursively Enumerable Sets as Pseudo- Diophantine

1995 ◽  
Vol 123 (2) ◽  
pp. 555
Author(s):  
Kostas Skandalis
Keyword(s):  
Recursively Enumerable ◽  
Recursively Enumerable Sets

scholarly journals When catalytic P systems with one catalyst can be computationally complete

2021 ◽  
Author(s):  
Artiom Alhazov ◽  
Rudolf Freund ◽  
Sergiu Ivanov
Keyword(s):  
Computational Complexity ◽  
P Systems ◽  
Membrane Systems ◽  
Computational Completeness ◽  
Recursively Enumerable ◽  
Recursively Enumerable Sets

AbstractCatalytic P systems are among the first variants of membrane systems ever considered in this area. This variant of systems also features some prominent computational complexity questions, and in particular the problem of using only one catalyst in the whole system: is one catalyst enough to allow for generating all recursively enumerable sets of multisets? Several additional ingredients have been shown to be sufficient for obtaining computational completeness even with only one catalyst. In this paper, we show that one catalyst is sufficient for obtaining computational completeness if either catalytic rules have weak priority over non-catalytic rules or else instead of the standard maximally parallel derivation mode, we use the derivation mode maxobjects, i.e., we only take those multisets of rules which affect the maximal number of objects in the underlying configuration.

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