title: Partially ordered acts and biacts
reg no: ETF6238
project type: Estonian Science Foundation research grant
status: accepted
institution: University of Tartu
head of project: Mati Kilp
duration: 01.01.2005 - 31.12.2008
description: Following results of the articles [Fakhruddin, S. M., Absolute flatness and amalgams in pomonoids, Semigroup Forum 33, 1986, 15-22] and [Shi, X., Liu, Z., Wang, F. and S. Bulman-Fleming, Indecomposable, projective and flat S-posets, Comm. Algebra, to appear] it is planned to investigate flatness properties of partially ordered acts (S-posets) over partially ordered monoids S. As the authors of these papers have generalised concepts of the theory of ordinary (i.e. unordered) acts in different ways, the first task is to fix the most suitable set of concepts for this situation. It is possible that several versions of flatness theory arise (for example depending on whether one requires convexity of subacts or not). In this analyses it is planned to consider all main types of flatness starting from torsion freeness until freeness (see [Kilp, M., Knauer U. and A. V. Mikhalev, Monoids, Acts and Categories, Walter de Gruyter, Berlin, New York, 2000]) and their generalisations considered later (see [Bulman-Fleming, S., Kilp, M., Equalizers and flatness properties of acts, Communications in Algebra 30, 2002, 1475-1498], [Laan, V., Pullbacks and flatness properties of acts I, Comm. Algebra 29 (2), 2001, 829-850] ).
Biacts (and perhaps also partially ordered biacts) over two different monoids are special cases of certain functors, so called distributors. Tensor multiplication by biacts has an important role in two fields: descent theory and investigations of Morita equivalence. It will be tried to generalise the results proved using biacts (e.g. in [Laan, V., On descent theory for monoid actions, Theory Appl. Categories, to appear] and [Knauer, U., Morita Äquivalenz von Halbgruppen, dissertation, Bielefeld, 1971]) to the case of distributors.

project group
no name institution position  
1.Mati KilpUniversity of Tartuprofessor 
2.Valdis LaanUniversity of TartuSenior Researcher