Preservation of notion of C sets near zero over reals

Abstract

There are several notions of largeness in a semigroup. N. Hindman and D. Strauss established that if $u,v \in \mathbb{N}$, $A$ is a $u \times v$ matrix with entries from $\mathbb{Q}$ and $\psi$ is a notion of a large set in $\mathbb{N}$, then $\{\vec{x} \in \mathbb{N}^v: A\vec{x} \in \psi^u \}$ is large in $\mathbb{N}^v$. Among the several notions of largeness, C sets occupies an important place of study because they exhibit strong combinatorial properties. The analogous notion of C set appears for a dense subsemigroup $S$ of $((0, \infty),+)$ called a C-set near zero. These sets also have very rich combinatorial structure. In this article, we investigate the above result for C sets near zero in $\mathbb{R}^+$ when the matrix has real entries. We also develop a new characterisation of C-sets near zero in $\mathbb{R}^+$.