شماره ركورد كنفرانس :
3735
عنوان مقاله :
(ON THE FUNCTIONALLY SEPRABLE SUBALGEBRA OF C(X
پديدآورندگان :
Namdari M namdari@ipm.ac.ir Shahid Chamran University of Ahvaz , Soltanpour S s.soltanpour@put.ac.ir Petroleum University of TechnologyAhvaz
كليدواژه :
Functionally countable , Seprable , Scattered space , P , space.
عنوان كنفرانس :
اولين كنفرانس منطقه اي علوم رياضي و كاربردها
چكيده فارسي :
Let $C_c(X)=\{f\in C(X) : |f(X)|\leq \aleph_0\}$, $C^F(X)=\{f\in C(X): |f(X)| \infty\}$. If $C_c(X)=C(X)$ ($C^F(X)=C(X)$), then $X$ is called functionally countable (finite). We define functionally seprable subalgebra of $C(X)$ as $C_{cd}(X)=\{f\in C(X): |f(Y)|\leq\aleph_0\}$ where $Y$ is a dense subset of $X$.
We observe that $C_c(X)\subseteq C_{cd}(X)\subseteq C_c(Y)$ and $C_{cd}(X)$ enjoys most of the important properties which are shared by $C(X)$ and $C_c(X)$.
Spaces $X$ such that $C_c(X)=C_{cd}(X)$ are investigated.
If $X$ is a functionally countable or seprable space then $C_{cd}(X)=C(X)$.
Let $X$ be pseudocompact (i.e., $C(X)=C^*(X)$) and $\beta X$ be seprable, then $C_{cd}(X)=C(X)$. Conversely if $C_{cd}(X)=C(X)$ and any $G_{\delta}$-set has nonempty interior, then $X$ is functionally countable.
We also observe that for a pseudocompact space $X$, $C_{cd}(X)=C(X)$ if and only if $C_{cd}(\beta X)=C(\beta X)$.