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THE FINITE BASIS PROBLEM FOR THE MONOID OF TWO-BY-TWO UPPER TRIANGULAR TROPICAL MATRICES
Published online by Cambridge University Press: 08 January 2016
Abstract
For each positive $n$, let
$\mathbf{u}_{n}\approx \boldsymbol{v}_{n}$ denote the identity obtained from the Adjan identity
$(xy)(yx)(xy)(xy)(yx)\approx (xy)(yx)(yx)(xy)(yx)$ by substituting
$(xy)\rightarrow (x_{1}x_{2}\ldots x_{n})$ and
$(yx)\rightarrow (x_{n}\ldots x_{2}x_{1})$. We show that every monoid which satisfies
$\mathbf{u}_{n}\approx \boldsymbol{v}_{n}$ for each positive
$n$ and generates a variety containing the bicyclic monoid is nonfinitely based. This implies that the monoid
$U_{2}(\mathbb{T})$ (respectively,
$U_{2}(\overline{\mathbb{Z}})$) of two-by-two upper triangular tropical matrices over the tropical semiring
$\mathbb{T}=\mathbb{R}\cup \{-\infty \}$ (respectively,
$\overline{\mathbb{Z}}=\mathbb{Z}\cup \{-\infty \}$) is nonfinitely based.
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- Research Article
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- © 2016 Australian Mathematical Publishing Association Inc.
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