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Combinatorial topology and the global dimension of algebras arising in combinatorics

Stuart Margolis, Franco Saliola, Benjamin Steinberg (2015)

Journal of the European Mathematical Society

In a highly influential paper, Bidigare, Hanlon and Rockmore showed that a number of popular Markov chains are random walks on the faces of a hyperplane arrangement. Their analysis of these Markov chains took advantage of the monoid structure on the set of faces. This theory was later extended by Brown to a larger class of monoids called left regular bands. In both cases, the representation theory of these monoids played a prominent role. In particular, it was used to compute the spectrum of the...

Combinatorics and quantifiers

Jaroslav Nešetřil (1996)

Commentationes Mathematicae Universitatis Carolinae

Let I m be the set of subsets of I of cardinality m . Let f be a coloring of I m and g a coloring of I m . We write f g if every f -homogeneous H I is also g -homogeneous. The least m such that f g for some f : I m k is called the k -width of g and denoted by w k ( g ) . In the first part of the paper we prove the existence of colorings with high k -width. In particular, we show that for each k > 0 and m > 0 there is a coloring g with w k ( g ) = m . In the second part of the paper we give applications of wide colorings in the theory of generalized quantifiers....

Combinatorics of Dyadic Intervals: Consistent Colourings

Anna Kamont, Paul F. X. Müller (2014)

Bulletin of the Polish Academy of Sciences. Mathematics

We study the problem of consistent and homogeneous colourings for increasing families of dyadic intervals. We determine when this problem can be solved and when it cannot.

Combinatorics of open covers (VII): Groupability

Ljubiša D. R. Kočinac, Marion Scheepers (2003)

Fundamenta Mathematicae

We use Ramseyan partition relations to characterize: ∙ the classical covering property of Hurewicz; ∙ the covering property of Gerlits and Nagy; ∙ the combinatorial cardinal numbers and add(ℳ ). Let X be a T 31 / 2 -space. In [9] we showed that C p ( X ) has countable strong fan tightness as well as the Reznichenko property if, and only if, all finite powers of X have the Gerlits-Nagy covering property. Now we show that the following are equivalent: 1. C p ( X ) has countable fan tightness and the Reznichenko property. 2....

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