It is a classical result of Shapirovsky that any compact space of countable tightness has a point-countable π-base. We look at general spaces with point-countable π-bases and prove, in particular, that, under the Continuum Hypothesis, any Lindelöf first countable space has a point-countable π-base. We also analyze when the function space $C_p\left(X\right)$ has a point-countable π -base, giving a criterion for this in terms of the topology of X when l*(X) = ω. Dealing with point-countable π-bases makes it possible...

We show that if $X$ is a ${\Sigma }_1^1$ separable metrizable space which is not $\sigma$-compact then $C_p^{*}\left(X\right)$, the space of bounded real-valued continuous functions on $X$ with the topology of pointwise convergence, is Borel-${\Pi }_1^1$-complete. Assuming projective determinacy we show that if $X$ is projective not $\sigma$-compact and $n$ is least such that $X$ is ${\Sigma }_n^1$ then $C_p\left(X\right)$, the space of real-valued continuous functions on $X$ with the topology of pointwise convergence, is Borel-${\Pi }_n^1$-complete. We also prove a simultaneous improvement of theorems of Christensen...

It is known that the ring $B\left(ℝ\right)$ of all Baire functions carrying the pointwise convergence yields a sequential completion of the ring $C\left(ℝ\right)$ of all continuous functions. We investigate various sequential convergences related to the pointwise convergence and the process of completion of $C\left(ℝ\right)$. In particular, we prove that the pointwise convergence fails to be strict and prove the existence of the categorical ring completion of $C\left(ℝ\right)$ which differs from $B\left(ℝ\right)$.

Introduciamo una nuova classe di topologie in spazi di funzioni derivanti da prossimità sul rango, che denotiamo sinteticamente PSOTs, acronimo di proximal set-open topologies. Le PSOTs sono una naturale generalizzazione delle classiche topologie di tipo set-open quando l'ordinaria inclusione viene sostituita con l'inclusione stretta associata ad una prossimità. Molte e note topologie di tipo set-open connesse a speciali networks sono esempi di PSOTs. Ogni PSOT è contraibile ad un sottospazio chiuso...

Given a Tychonoff space $X$, a base $\alpha$ for an ideal on $X$ is called pseudouniform if any sequence of real-valued continuous functions which converges in the topology of uniform convergence on $\alpha$ converges uniformly to the same limit. This paper focuses on pseudouniform bases for ideals with particular emphasis on the ideal of compact subsets and the ideal of all countable subsets of the ground space.