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APPROXIMATING TREES AS COLOURED LINEAR ORDERS AND COMPLETE AXIOMATISATIONS OF SOME CLASSES OF TREES

Published online by Cambridge University Press:  08 June 2021

RUAAN KELLERMAN
Affiliation:
DEPARTMENT OF MATHEMATICS AND APPLIED MATHEMATICS UNIVERSITY OF PRETORIAPRETORIA, SOUTH AFRICAE-mail:[email protected]
VALENTIN GORANKO
Affiliation:
DEPARTMENT OF PHILOSOPHY STOCKHOLM UNIVERSITYSTOCKHOLM, SWEDEN and SCHOOL OF MATHEMATICS (VISITING PROFESSORSHIP) UNIVERSITY OF THE WITWATERSRAND JOHANNESBURG, SOUTH AFRICA E-mail:[email protected]

Abstract

We study the first-order theories of some natural and important classes of coloured trees, including the four classes of trees whose paths have the order type respectively of the natural numbers, the integers, the rationals, and the reals. We develop a technique for approximating a tree as a suitably coloured linear order. We then present the first-order theories of certain classes of coloured linear orders and use them, along with the approximating technique, to establish complete axiomatisations of the four classes of trees mentioned above.

Type
Article
Copyright
© Association for Symbolic Logic 2021

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