174 research outputs found
On a problem of Henning and Yeo about the transversal number of uniform linear systems whose 2-packing number is fixed
For , let be an -uniform linear system. The
transversal number of is the minimum
number of points that intersect every line of . The 2-packing
number of is the maximum number of
lines such that the intersection of any three of them is empty. In [Discrete
Math. 313 (2013), 959--966] Henning and Yeo posed the following question: Is it
true that if is a -uniform linear system then
holds for
all ?. In this paper, some results about of -uniform linear systems
whose 2-packing number is fixed which satisfies the inequality are given
Transversal numbers over subsets of linear spaces
Let be a subset of . It is an important question in the
theory of linear inequalities to estimate the minimal number such that
every system of linear inequalities which is infeasible over has a
subsystem of at most inequalities which is already infeasible over
This number is said to be the Helly number of In view of Helly's
theorem, and, by the theorem due to Doignon, Bell and
Scarf, We give a common extension of these equalities
showing that We show that
the fractional Helly number of the space (with the
convexity structure induced by ) is at most as long as
is finite. Finally we give estimates for the Radon number of mixed
integer spaces
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