Tukey order are used to compare the cofinal complexity of partially order sets (posets). We prove that there is a $2^\mathfrak{ c}$-sized collection of sub-posets in $2^\omega$ which forms an antichain in the sense of Tukey ordering. Using the fact that any boundedly-complete sub-poset of $\omega^\omega$ is a Tukey quotient of $\omega^\omega$, we answer two open questions published in \cite{ FKL16}. The relation between $P$-base and strong Pytkeev$^\ast$ property is investigated. Let $P$ be a poset equipped with a second-countable topology in which every convergent sequence is bounded. Then we prove that any topological space with a $P$-base has the strong Pytkeev$^\ast$ property. Furthermore, we prove that every uncountably-dimensional locally convex space (lcs) with a $P$-base contains an infinite-dimensional metrizable compact subspace. Examples in function spaces are given.
Categories: math.GN