Resumen de New characterizations of T0-spaces

Josep Guia i Marín , Rafael Lledó, Isabel Segura

• Making use of the essential derived operator, we present some new characterizations of $T_0$-spaces in the same way that the already known for $T_D$ and $ET_D$-spaces. It is also proved that an analogous treatment for $T_1, ET_1=R_0,T_{UD}$ and $ET_{UD}$ spaces is not valid.