1,656 research outputs found
Techniques for approaching the dual Ramsey property in the projective hierarchy
We define the dualizations of objects and concepts which are essential for
investigating the Ramsey property in the first levels of the projective
hierarchy, prove a forcing equivalence theorem for dual Mathias forcing and
dual Laver forcing, and show that the Harrington-Kechris techniques for proving
the Ramsey property from determinacy work in the dualized case as well
Some new directions in infinite-combinatorial topology
We give a light introduction to selection principles in topology, a young
subfield of infinite-combinatorial topology. Emphasis is put on the modern
approach to the problems it deals with. Recent results are described, and open
problems are stated. Some results which do not appear elsewhere are also
included, with proofs.Comment: Small update
Norms on possibilities I: forcing with trees and creatures
We present a systematic study of the method of "norms on possibilities" of
building forcing notions with keeping their properties under full control. This
technique allows us to answer several open problems, but on our way to get the
solutions we develop various ideas interesting per se.These include a new
iterable condition for ``not adding Cohen reals'' (which has a flavour of
preserving special properties of p-points), new intriguing properties of
ultrafilters (weaker than being Ramsey but stronger than p-point) and some new
applications of variants of the PP--property.Comment: accepted for Memoirs of the Amer. Math. So
Selection principles in mathematics: A milestone of open problems
We survey some of the major open problems involving selection principles,
diagonalizations, and covering properties in topology and infinite
combinatorics. Background details, definitions and motivations are also
provided.Comment: Small update
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