Sacks forcing collapses to
We shall prove that Sacks algebra is nowhere -distributive, which implies that Sacks forcing collapses to .
Selfduality of the system of convex subsets of a partially ordered set
For a partially ordered set let us denote by the system of all convex subsets of . It is found the necessary and sufficient condition (concerning ) under which (as a partially ordered set) is selfdual.
Selfduality of the system of intervals of a partially ordered set
Semi-closure mappings and cofinal chains
Semigroups of order-decreasing transformations: the isomorphism theorem.
Semigroups of order-preserving partial endomorphisms on trees, I
Semi-ideals in semi-lattices
Semilattice structures on trees.
Semilattices of bisimple inverse semigroups.
Semilattices of finite arithmetical algebras
Semilattices of groups with distributive congruence lattice.
Semilattices of width 3 whose decomposable elements form a chain.
Semilattices which must contain a copy of 2 N.
Semilattices with sectional mappings
We consider join-semilattices with 1 where for every element p a mapping on the interval [p,1] is defined; these mappings are called sectional mappings and such structures are called semilattices with sectional mappings. We assign to every semilattice with sectional mappings a binary operation which enables us to classify the cases where the sectional mappings are involutions and / or antitone mappings. The paper generalizes results of [3] and [4], and there are also some connections to [1].
Semimatroids and their Tutte polynomials.
Semi-ordered groups
Semiorders and Riordan numbers.
Semi-valuation et métrique associée
Sequential structures induced by merotopies
Set families with a forbidden subposet.