Definability of closure operations in the <Emphasis Type="Italic">h</Emphasis>-quasiorder of labeled forests |
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Authors: | A V Zhukov O V Kudinov V L Selivanov |
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Institution: | 1.Novosibirsk State Pedagogical University,Novosibirsk,Russia;2.Sobolev Institute of Mathematics, Siberian Branch,Russian Academy of Sciences,Novosibirsk,Russia;3.Ershov Institute of Informatics Systems, Siberian Branch,Russian Academy of Sciences,Novosibirsk,Russia |
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Abstract: | We prove that natural closure operations on quotient structures of the h-quasiorder of finite and (at most) countable k-labeled forests (k ≥ 3) are definable provided that minimal nonsmallest elements are allowed as parameters. This strengthens our previous result
which holds that each element of the h-quasiorder of finite k-labeled forests is definable in the first-order language, and each element of the h-quasiorder of (at most) countable k-labeled forests is definable in the language L
ω1ω; in both cases k ≥ 3 and minimal nonsmallest elements are allowed as parameters. Similar results hold true for two other relevant structures:
the h-quasiorder of finite (resp. countable) k-labeled trees and k-labeled trees with a fixed label on the root element. |
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