Victor L. Selivanov

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The boolean hierarchy of partitions was introduced and studied by K. Wagner and S. Kosub, mostly over the lattice of NP -sets. We consider this hierarchy for the case of lattices having the reduction property and show that in this case the hierarchy behaves much easier and admits a deeper investigation. We completely characterize the hierarchy over some(More)
By applying descriptive set theory to the Wagner’s fine structure of regular ω-languages we get quite different proofs of his results and obtain new results. We give an automata-free description of the fine structure. We present also a simple property of a deterministic Muller automaton equivalent to the condition that the corresponding regular ω-language(More)
We prove that for any k ≥ 3 each element of the homomorphic quasiorder of finite k-labeled forests is definable, provided that the minimal non-smallest elements are allowed as parameters. As corollaries, we show that the structure is atomic and characterize the automorphism group of the structure. Similar results hold true for two other relevant structures:(More)