In this article we study the comaximal graph ${\Gamma }_{{}_2}^{\text{'}}C\left(X\right)$ of the ring $C\left(X\right)$. We have tried to associate the graph properties of ${\Gamma }_{{}_2}^{\text{'}}C\left(X\right)$, the ring properties of $C\left(X\right)$ and the topological properties of $X$. Radius, girth, dominating number and clique number of the ${\Gamma }_{{}_2}^{\text{'}}C\left(X\right)$ are investigated. We have shown that $2\le Rad{\Gamma }_{{}_2}^{\text{'}}C\left(X\right)\le 3$ and if $\left|X\right|>2$ then $\mathrm{girth}{\Gamma }_{{}_2}^{\text{'}}C\left(X\right)=3$. We give some topological properties of $X$ equivalent to graph properties of ${\Gamma }_{{}_2}^{\text{'}}C\left(X\right)$. Finally we have proved that $X$ is an almost $P$-space which does not have isolated points if and only if $C\left(X\right)$ is an almost regular ring...

If $X$ is a space that can be mapped onto a metric space by a one-to-one mapping, then $X$ is said to have a weaker metric topology. In this paper, we give characterizations of sequence-covering compact images and sequentially-quotient compact images of spaces with a weaker metric topology. The main results are that (1) $Y$ is a sequence-covering compact image of a space with a weaker metric topology if and only if $Y$ has a sequence ${\left\{{ℱ}_i\right\}}_{i\in \mathbb{N}}$ of point-finite $cs$-covers such that ${\bigcap }_{i\in \mathbb{N}}\mathrm{st}(y,{ℱ}_i)=\left\{y\right\}$ for each $y\in Y$. (2) $Y$ is a sequentially-quotient...

We conduct an investigation of the relationships which exist between various generalizations of complete regularity in the setting of merotopic spaces, with particular attention to filter spaces such as Cauchy spaces and convergence spaces. Our primary contribution consists in the presentation of several counterexamples establishing the divergence of various such generalizations of complete regularity. We give examples of: (1) a contigual zero space which is not weakly regular and is not a Cauchy...

In this article we define the $m$-topology on some rings of quotients of $C\left(X\right)$. Using this, we equip the classical ring of quotients $q\left(X\right)$ of $C\left(X\right)$ with the $m$-topology and we show that $C\left(X\right)$ with the $r$-topology is in fact a subspace of $q\left(X\right)$ with the $m$-topology. Characterization of the components of rings of quotients of $C\left(X\right)$ is given and using this, it turns out that $q\left(X\right)$ with the $m$-topology is connected if and only if $X$ is a pseudocompact almost $P$-space, if and only if $C\left(X\right)$ with $r$-topology is connected. We also observe that...

Let $C_F\left(X\right)$ be the socle of C(X). It is shown that each prime ideal in $C\left(X\right)/C_F\left(X\right)$ is essential. For each h ∈ C(X), we prove that every prime ideal (resp. z-ideal) of C(X)/(h) is essential if and only if the set Z(h) of zeros of h contains no isolated points (resp. int Z(h) = ∅). It is proved that $dim(C\left(X\right)/C_F\left(X\right))\ge dimC\left(X\right)$, where dim C(X) denotes the Goldie dimension of C(X), and the inequality may be strict. We also give an algebraic characterization of compact spaces with at most a countable number of nonisolated points. For each essential...

It is shown how to embed the polydisk algebras (finite and infinite ones) into the disk algebra A(𝔻̅). As a consequence, one obtains uniform closed subalgebras of A(𝔻̅) which have arbitrarily prescribed stable ranks.

On présente dans cet exposé une approche semi-classique déduite des résultats de N. Burq, P. Gérard et N. Tzvetkov [4] permettant de démontrer des inégalités de Strichartz pour un problème non captif. On retrouve ainsi des résultats de G. Staffilani et D. Tataru [16] (obtenus pour une perturbation de la métrique à support compact). On donne aussi des généralisations de ces résultats au cas d’une perturbation à longue portée