Article
Keywords:
separation axioms; box product; ultraproduct; ideal product topology
Summary:
We give sufficient and necessary conditions to be fulfilled by a filter $\Psi $ and an ideal $\Lambda $ in order that the $\Psi $-quotient space of the $\Lambda $-ideal product space preserves $T_k$-properties ($k=0,1,2,3,3\frac{1}{2}$) (``in the sense of the \L os theorem''). Tychonoff products, box products and ultraproducts appear as special cases of the general construction.
References:
[2] van Douwen E.K.:
The box product of countably many metrizable spaces need not be normal. Fundamenta Mathematicae LXXXVIII.2 (1975), 127-132.
MR 0385781
[4] Kelly J.L.: General Topology. Springer Verlag, Graduate Texts in Mathematics 27.