377 research outputs found
Special effect varieties in higher dimension
Here we introduce the concept of special effect varieties in higher dimension
and we generalize to the n-dimensional projective space, n>=3, the two
conjectures given in AG/0410527 for the planar case. Finally, we propose some
examples on the product of projective spaces and we show how these results fit
with the ones of Catalisano, Geramita and Gimigliano.Comment: 24 page
Waldschmidt constants for Stanley-Reisner ideals of a class of Simplicial Complexes
We study the symbolic powers of the Stanley-Reisner ideal of a
bipyramid over a gon . Using a combinatorial approach, based on
analysis of subtrees in we compute the Waldschmidt constant of .Comment: 10 pages, 2 figure
Geometry of diagonal-effect models for contingency tables
In this work we study several types of diagonal-effect models for two-way
contingency tables in the framework of Algebraic Statistics. We use both toric
models and mixture models to encode the different behavior of the diagonal
cells. We compute the invariants of these models and we explore their
geometrical structure.Comment: 20 page
Waldschmidt constants for Stanley-Reisner ideals of a class of graphs
In the present note we study Waldschmidt constants of Stanley-Reisner ideals
of a hypergraph and a graph with vertices forming a bipyramid over a planar
n-gon. The case of the hypergraph has been studied by Bocci and Franci. We
reprove their main result. The case of the graph is new. Interestingly, both
cases provide series of ideals with Waldschmidt constants descending to 1. It
would be interesting to known if there are bounded ascending sequences of
Waldschmidt constants.Comment: 7 pages, 2 figure
Realization of distance matrices by unicyclic graphs
Given a distance matrix D, we study the behavior of its compaction vector and
reduction matrix with respect to the problem of the realization of D by a weighted graph. To
this end, we first give a general result on realization by n−cycles and successively we mainly
focus on unicyclic graphs, presenting an algorithm which determines when a distance matrix
is realizable by such a kind of graph, and then, shows how to construct it
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