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Generalisations of disjunctive sequences
Author(s) -
Calude Cristian S.,
Staiger Ludwig
Publication year - 2005
Publication title -
mathematical logic quarterly
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.473
H-Index - 28
eISSN - 1521-3870
pISSN - 0942-5616
DOI - 10.1002/malq.200310130
Subject(s) - sequence (biology) , mathematics , set (abstract data type) , cantor set , finite set , discrete mathematics , computer science , mathematical analysis , genetics , biology , programming language
The present paper proposes a generalisation of the notion of disjunctive (or rich) sequence, that is, of an infinite sequence of letters having each finite sequence as a subword. Our aim is to give a reasonable notion of disjunctiveness relative to a given set of sequences F . We show that a definition like “every subword which occurs at infinitely many different positions in sequences in F has to occur infinitely often in the sequence” fulfils properties similar to the original unrelativised notion of disjunctiveness. Finally, we investigate our concept of generalised disjunctiveness in spaces of Cantor expansions of reals. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)