Precise bounds for the sequential order of products of some Frechet topologies

The sequential order of a topological space is the least ordinal for which the corresponding iteration of the sequential closure is idempotent. Lower estimates for the sequential order of the product of two regular Frechet topologies and upper estimates for the sequential order of the product of two subtransverse topologies, are given in terms of their fascicularity and sagittality. It is shown that for every countable ordinal alpha, there exists a Lasnev topology such that the sequential order of its square is equal to alpha. (C) 1998 Elsevier Science B.V.