Journal of Mathematical Sciences: Advances and Applications
CLOSED SETS AND ALMOST NORMALITY OF THE
NIEMYTZKI PLANE TOPOLOGYAuthor's: Sadeq Ali Saad Thabit and Hailiza Kamarulhaili
Pages: [73] - [85]
Received Date: April 25, 2011
Submitted by:
The Niemytzki plane topology is a famous example of a Tychonoff space,
which is quasi-normal but not normal. In this paper, we show that it
is almost normal but not semi-normal. Also, we give some short notes
on a class of sets in topological spaces called 
-closed sets, which introduced by Zaitsev in
1968. This class of sets is strictly placed between closed domain sets
and closed sets. Practically, some basic properties of -closed sets are presented.
closed domain, open domain, normal, semi-normal, quasi-normal, almost
normal, mildly normal, -open set, -closed set.
