S. I. Mardaev, “Submodel Defining Formulas”, Vestn. Novosib. Gos. Univ., Ser. Mat. Mekh. Inform., 2011, Volume 11, Issue 1,Pages <nobr>82

Submodel Defining Formulas

S. I. Mardaev^ab

^a Sobolev Institute of Mathematics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk
^b Novosibirsk State University

Abstract: Least fixed points of modal formulas are investigated. A concept of submodel defining formula is introduced and it is proved that for each formula positive in special variable there exists a submodel defining formula for every transitive model. This formula is constructed by simple algorithm and preserve positivity of parameters.

Keywords: non-standard logics, modal logics, fixed points, positive operators, model, frame.

UDC: 510.64

Received: 18.11.2009