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Countable chains of distributive lattices as maximal semilattice quotients of positive cones of dimension groups

Pavel Růžička (2006)

Commentationes Mathematicae Universitatis Carolinae

We construct a countable chain of Boolean semilattices, with all inclusion maps preserving the join and the bounds, whose union cannot be represented as the maximal semilattice quotient of the positive cone of any dimension group. We also construct a similar example with a countable chain of strongly distributive bounded semilattices. This solves a problem of F. Wehrung.

Degeneration of Schubert varieties of S L n / B to toric varieties

Raika Dehy, Rupert W.T. Yu (2001)

Annales de l’institut Fourier

Using the polytopes defined in an earlier paper, we show in this paper the existence of degeneration of a large class of Schubert varieties of S L n to toric varieties by extending the method used by Gonciulea and Lakshmibai for a miniscule G / P to Schubert varieties in S L n .

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