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The covering radius problem for sets of perfect matchings
Consider the family of all perfect matchings of the complete graph
with vertices. Given any collection of perfect matchings of
size , there exists a maximum number such that if ,
then there exists a perfect matching that agrees with each perfect matching in
in at most edges. We use probabilistic arguments to give
several lower bounds for . We also apply the Lov\'asz local lemma to
find a function such that if each edge appears at most times
then there exists a perfect matching that agrees with each perfect matching in
in at most edges. This is an analogue of an extremal result
vis-\'a-vis the covering radius of sets of permutations, which was studied by
Cameron and Wanless (cf. \cite{cameron}), and Keevash and Ku (cf. \cite{ku}).
We also conclude with a conjecture of a more general problem in hypergraph
matchings.Comment: 10 page
Non-homeomorphic topological rank and expansiveness
Downarowicz and Maass (2008) have shown that every Cantor minimal
homeomorphism with finite topological rank is expansive. Bezuglyi,
Kwiatkowski and Medynets (2009) extended the result to non-minimal cases. On
the other hand, Gambaudo and Martens (2006) had expressed all Cantor minimal
continuou surjections as the inverse limit of graph coverings. In this paper,
we define a topological rank for every Cantor minimal continuous surjection,
and show that every Cantor minimal continuous surjection of finite topological
rank has the natural extension that is expansive
Properties of Bipolar Fuzzy Hypergraphs
In this article, we apply the concept of bipolar fuzzy sets to hypergraphs
and investigate some properties of bipolar fuzzy hypergraphs. We introduce the
notion of tempered bipolar fuzzy hypergraphs and present some of their
properties. We also present application examples of bipolar fuzzy hypergraphs
A Geometric Perspective on Sparse Filtrations
We present a geometric perspective on sparse filtrations used in topological
data analysis. This new perspective leads to much simpler proofs, while also
being more general, applying equally to Rips filtrations and Cech filtrations
for any convex metric. We also give an algorithm for finding the simplices in
such a filtration and prove that the vertex removal can be implemented as a
sequence of elementary edge collapses
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