The lattice of ordinable topologies

We demonstrate that the ordinable topologies for a set X areprecisely those that occupy the upper part of the lattice of topologies for X, and that they determine a lattice, not always complete or distributive. We also found the amount of complements, and principal complements, for certainordinable topologies, generalizing a known result of P. S. Schnare

Acerca del retículo de las pretopologías sobre un conjunto X

Mostramos que (Pretop(X), <=), el retículo de las pretopologías sobre un conjunto arbitrario X, siempre tiene un esqueleto, y presentamos una caracterización de los coátomos en Pretop(X) en términos de ultratopologías sobre X.    We show that (Pretop(X), <=), the lattice of pretopologies on an arbitrary set X, always has a framework; we present a characterization of the co-atoms in Pretop(X) in terms of ultratopologies on X

Upward Morley's theorem downward

By a celebrated theorem of Morley, a theory T is א1-categorical if and only if it is κ-categorical for all uncountable κ. In this paper we are taking the first steps towards extending Morley's categoricity theorem "to the finite". In more detail, we are presenting conditions, implying that certain finite subsets of certain א1-categorical T have at most one n-element model for each natural number n∈ω (counting up to isomorphism, of course). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim