On the quasi-transversals of a matroid
نویسندگان
چکیده
We show that the set of r-quasi-transversals of a matroid, if nonempty, is the set of bases of a matroid. We also give an alternative proof of the known theorem which identifies the conjugate of the rank partition of a matroid.
منابع مشابه
Local equivalence of transversals in matroids
Given any system of n subsets in a matroid M , a transversal of this system is an n-tuple of elements of M , one from each set, which is independent. Two transversals differing by exactly one element are adjacent, and two transversals connected by a sequence of adjacencies are locally equivalent, the distance between them being the minimum number of adjacencies in such a sequence. We give two s...
متن کاملTransversals and Matroid Partition*
In sec tion 1, transversal Inatroids are assoc iated with "syste ms of di s tinct represe ntatives" (i. e., tra nsversals) and,. more generally , matc hing matroids are associated with matc hings in graphs . Th e transversal matrolds and a theore m of P. J. Higgins on disjoint transversals of a famil y of se ts , along wIth th e well-known graphIc matrold s a nd some theorems on decomposition o...
متن کاملDisjoint Common Transversals and Exchange Structures
We state and prove a theorem (Theorem 1 below) which strengthens previously known results concerning disjoint common partial transversals of two families of sets. This theorem may be viewed as a result on transversal pre-independence structures. We define a "disjoint-exchange structure" on a set and extend the result to such structures (Theorem 3 below). Then we give an application of this theo...
متن کاملWei-type duality theorems for matroids
We present several fundamental duality theorems for matroids and more general combinatorial structures. As a special case, these results show that the maximal cardinalities of fixed-ranked sets of a matroid determine the corresponding maximal cardinalities of the dual matroid. Our main results are applied to perfect matroid designs, graphs, transversals, and linear codes over division rings, in...
متن کاملCodimension two and three Kneser Transversals
Let k, d, λ > 1 be integers with d > λ and let X ⊂ R be a finite set. A (d−λ)-plane L transversal to the convex hull of all k-sets of X is called Kneser transversal. If in addition L contains (d− λ) + 1 points of X, then L is called complete Kneser transversal. In this paper, we present various results on the existence of (complete) Kneser transversals for λ = 2, 3. In order to do this, we intr...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Discrete Mathematics
دوره 146 شماره
صفحات -
تاریخ انتشار 1995