منابع مشابه
Complexities of relational structures
The relational complexity, introduced by G. Cherlin, G. Martin, and D. Saracino, is a measure of ultrahomogeneity of a relational structure. It provides an information on minimal arity of additional invariant relations needed to turn given structure into an ultrahomogeneous one. The original motivation was group theory. This work focuses more on structures and provides an alternative approach. ...
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How do we compare the complexities of various classes of structures? The Turing ordinal of a class of structures, introduced by Jockusch and Soare, is defined in terms of the number of jumps required for coding to be possible. The back-and-forth ordinal, introduced by Montalbán, is defined in terms of Σα-types. The back-and-forth ordinal is (roughly) bounded by the Turing ordinal. In this paper...
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ژورنال
عنوان ژورنال: Mathematica Slovaca
سال: 2015
ISSN: 1337-2211,0139-9918
DOI: 10.1515/ms-2015-0019