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JOURNALS // Trudy Instituta Matematiki i Mekhaniki UrO RAN // Archive

Trudy Inst. Mat. i Mekh. UrO RAN, 2020 Volume 26, Number 3, Pages 171–186 (Mi timm1754)

Automorphisms of the semiring of polynomials $\mathbb{R}_+^{\vee}[x]$ and lattices of its subalgebras

V. V. Sidorov

Vyatka State University

Abstract: A commutative semiring with zero and unity different from a ring where each nonzero element is invertible is called a semifield with zero. Let $\mathbb{R}^{\vee}_+$ be the semifield with zero of nonnegative real numbers with operations of max-addition and multiplication. For any positive real numbers $a$ and $s$, denote by $\psi_{a,s}$ the automorphism of the semiring of polynomials $\mathbb{R}_+^{\vee}[x]$ defined by the rule $\psi_{a, s}\colon a_0\vee a_1x\vee\ldots\vee a_nx^n\mapsto a_0^s\vee a_1^s(ax)\vee\ldots\vee a_n^s(ax)^n$. It is proved that the automorphisms of the semiring $\mathbb{R}_+^{\vee}[x]$ are exactly the automorphisms $\psi_{a, s}$. The ring $C(X)$ of continuous $\mathbb{R}$-valued functions defined on an arbitrary topological space $X$ is an algebra over the field $\mathbb{R}$ of real numbers. A subalgebra of $C(X)$ is any nonempty subset closed under addition and multiplication of functions and under multiplication by constants from $\mathbb{R}$. Similarly, we call a nonempty subset $A\subseteq \mathbb{R}_+^{\vee}[x]$ a subalgebra of $\mathbb{R}_+^{\vee}[x]$ if $f\vee g,fg,rf\in A$ for any $f, g\in A$ and $r\in\mathbb{R}^{\vee}_+$. It is proved that an arbitrary automorphism of the lattice of subalgebras of $\mathbb{R}_+^{\vee}[x]$ is induced by some automorphism of $\mathbb{R}_+^{\vee}[x]$. The same result also holds for the lattice of subalgebras with unity of the semiring $\mathbb{R}_+^{\vee}[x]$. The technique of one-generated subalgebras is applied.

Keywords: semiring of polynomials, lattice of subalgebras, automorphism, max-addition.

UDC: 512.556

MSC: 06B05, 16S60, 54H99

Received: 02.05.2020
Revised: 20.05.2020
Accepted: 01.06.2020

DOI: 10.21538/0134-4889-2020-26-3-171-186



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