Geodesic
On the сomplexity of quasivariety lattices
Sibirskie èlektronnye matematičeskie izvestiâ, Tome 14 (2017), pp. 92-97.

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We prove that any AD-class of algebraic structures of finite signature contains continuum many proper subclasses, which have the Nurakunov non-computability property, but which are not Q-universal (among those are almost all the known Q-universal quasivarieties nowadays). A similar result holds for some classes of algebraic structures of countable signature. This provides a negative answer to an open question.
Keywords: computable set, lattice, quasivariety, Q-universality. 
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S. M. Lutsak. On the сomplexity of quasivariety lattices. Sibirskie èlektronnye matematičeskie izvestiâ, Tome 14 (2017), pp. 92-97. http://geodesic.mathdoc.fr/item/SEMR_2017_14_a1/

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