8,196 research outputs found
The causal order on the ambient boundary
We analyse the causal structure of the ambient boundary, the conformal
infinity of the ambient (Poincar\'e) metric. Using topological tools we show
that the only causal relation compatible with the global topology of the
boundary spacetime is the horismos order. This has important consequences for
the notion of time in the conformal geometry of the ambient boundary.Comment: 7 page
Algebraic Topology of Calabi-Yau Threefolds in Toric Varieties
We compute the integral homology (including torsion), the topological
K-theory, and the Hodge structure on cohomology of Calabi-Yau threefold
hypersurfaces and complete intersections in Gorenstein toric Fano varieties.
The methods are purely topological
The Finite Basis Problem for Kiselman Monoids
In an earlier paper, the second-named author has described the identities
holding in the so-called Catalan monoids. Here we extend this description to a
certain family of Hecke--Kiselman monoids including the Kiselman monoids
. As a consequence, we conclude that the identities of
are nonfinitely based for every and exhibit a finite
identity basis for the identities of each of the monoids and
.
In the third version a question left open in the initial submission has beed
answered.Comment: 16 pages, 1 table, 1 figur
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