On the semigroup generating by extended bicyclic semigroup and a $\omega$-closed family

TL;DR

This paper introduces an algebraic extension of the extended bicyclic semigroup based on an $ ext{ω}$-closed family, analyzing its structure, relations, and conditions for various types of simplicity and isomorphisms.

Contribution

It defines and studies the properties of the semigroup $oldsymbol{B}_{ ext{Z}}^{ ext{F}}$, including its structure, Green's relations, and criteria for simplicity and isomorphism to known semigroups.

Findings

$oldsymbol{B}_{ ext{Z}}^{ ext{F}}$ is a combinatorial inverse semigroup.

Criteria for simplicity, $0$-simplicity, bisimplicity, and $0$-bisimplicity are established.

When $ ext{F}$ consists of singletons and empty set, $oldsymbol{B}_{ ext{Z}}^{ ext{F}}$ is isomorphic to the Brandt $ ext{λ}$-extension.

Abstract

The algebraic extension $\boldsymbol{B}_{\mathbb{Z}}^{\mathscr{F}}$ of the extended bicyclic semigroup for an arbitrary $\omega$-closed family $\mathscr{F}$ subsets of $\omega$ is introduced. It is proven that $\boldsymbol{B}_{\mathbb{Z}}^{\mathscr{F}}$ is a combinatorial inverse semigroup. Green's relations, the natural partial order on the semigroup $\boldsymbol{B}_{\mathbb{Z}}^{\mathscr{F}}$ and its set of idempotents are described. The criteria of simplicity, $0$-simplicity, bisimplicity, $0$-bisimplicity of the semigroup $\boldsymbol{B}_{\mathbb{Z}}^{\mathscr{F}}$ and the criterion for $\boldsymbol{B}_{\mathbb{Z}}^{\mathscr{F}}$ to be isomorphic to the extended bicyclic semigroup or the countable semigroup of matrix units are derived. It is proved that in the case when the family $\mathscr{F}$ consists of all singletons of $\omega$ and the empty set, the semigroup $\boldsymbol{B}_{\mathbb{Z}}^{\mathscr{F}}$ is isomorphic to the Brandt $\lambda$-extension of the semilattice $(\omega,\min)$.