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We show that the class of groups which have monoid presentations by means of finite special -confluent string-rewriting systems strictly contains the class of plain groups (the groups which are free products of a finitely generated free group and finitely many finite groups), and that any group which has an infinite cyclic central subgroup can be presented by such a string-rewriting system if and only if it is the direct product of an infinite cyclic group and a finite cyclic group.
We show that the class of groups which
have monoid presentations by means of finite special
[λ]-confluent string-rewriting systems strictly contains the class of plain groups
(the groups which are free products of a finitely generated free
group and finitely many finite groups),
and that any group
which has an infinite cyclic central subgroup
can be presented by such a string-rewriting system if and only if it is the
direct product of an infinite cyclic group and a finite cyclic group.
We study five extensions of the polymorphically typed lambda-calculus (system
F) by type constructs intended to model fixed-points of monotone
operators. Building on work by Geuvers
concerning the relation between term
rewrite systems for least pre-fixed-points and greatest post-fixed-points of
positive type schemes (i.e., non-nested positive inductive and coinductive
types) and so-called
retract types, we show that there are
reduction-preserving
embeddings even between systems of monotone (co)inductive...
Multigenerative grammar systems are based on cooperating context-free grammatical components that simultaneously generate their strings in a rule-controlled or nonterminal-controlled rewriting way, and after this simultaneous generation is completed, all the generated terminal strings are combined together by some common string operations, such as concatenation, and placed into the generated languages of these systems. The present paper proves that these systems are equivalent with the matrix grammars....
This paper discusses -island finite automata whose transition graphs can be expressed as -member sequences of islands , where there is a bridge leaving and entering for each . It concentrates its attention on even computation defined as any sequence of moves during which these automata make the same number of moves in each of the islands. Under the assumption that these automata work only in an evenly computational way, the paper proves its main result stating that -island finite automata...
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