Acta Math. Hungar., 136 (4) (2012), 233–239 DOI: 10.1007/s10474-012-0201-z First published online March 7, 2012 ON MAXIMAL μ-OPEN AND MINIMAL μ-CLOSED SETS VIA GENERALIZED TOPOLOGY B. ROY 1 and R. SEN 2,* 1 Department of Mathematics, Women’s Christian College, 6, Greek Church Row, Kolkata 700 026, India e-mail: bishwambhar roy@yahoo.co.in 2 Department of Mathematics, S. A. Jaipuria College, 10, Raja Naba Krishna Street, Kolkata 700 005, India e-mail: ritu sen29@yahoo.co.in (Received June 27, 2011; accepted October 6, 2011) Abstract. We introduce the notion of maximal μ-open and minimal μ- closed sets in a generalized topological space. We also investigate some of their fundamental properties. 1. Introduction For the last one decade or so, the researchers are concerned with the investigations of generalized topological spaces and several classes of gener- alized types of open sets. ´ A. Cs´ asz´ ar was the initiator of this direction of study. Generalized open sets play an important role in generalized topology and these are studied by many topologists. On the other hand, F. Nakaoka and N. Oda [4,5] introduced the notion of maximal open sets and minimal closed sets in topological spaces. The purpose of this paper is to introduce the concept of a new class of μ-open sets called maximal μ-open set, and also the idea of minimal μ-closed sets, and investigate some of their fundamental properties. A generalized topology (briefly, GT) [1] on a set X is a subset μ of the power set exp X such that ∅∈ μ and μ is closed under arbitrary union. The elements of μ are called μ-open sets and their complements are known as μ- closed sets. A set X , with a GT μ on it is said to be a generalized topological * Corresponding author. Key words and phrases: maximal μ-open set, minimal μ-closed set, almost maximal μ-open set. 2010 Mathematics Subject Classification: 54B05, 54C08. 0236-5294/$ 20.00 c  2012 Akad´ emiai Kiad´o, Budapest, Hungary