Pseudovarieties defining classes of sofic subshifts closed under taking shift equivalent subshifts |
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Authors: | Alfredo Costa |
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Institution: | CMUC, Universidade de Coimbra, Apartado 3008, 3001-454 Coimbra, Portugal |
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Abstract: | For a pseudovariety of ordered semigroups, let be the class of sofic subshifts whose syntactic semigroup lies in . It is proved that if contains then is closed under taking shift equivalent subshifts, and conversely, if is closed under taking conjugate subshifts then contains and . Almost finite type subshifts are characterized as the irreducible elements of , which gives a new proof that the class of almost finite type subshifts is closed under taking shift equivalent subshifts. |
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Keywords: | 20M07 37B10 20M35 |
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