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