منابع مشابه
Graphic Matroids
Matroid theory was first formalized in 1935 by Whitney [5] who introduced the notion as an attempt to study the properties of vector spaces in an abstract manner. Since then, matroids have proven to have numerous applications in a wide variety of fields including combinatorics and graph theory. Today we will briefly survey matroid representation and then discuss some problems in matroid optimiz...
متن کاملOn cographic matroids and signed-graphic matroids
We prove that a connected cographic matroid of a graph G is the bias matroid of a signed graph Σ iff G imbeds in the projective plane. In the case that G is nonplanar, we also show that Σ must be the projective-planar dual signed graph of an actual imbedding of G in the projective plane. As a corollary we get that, if G1, . . . , G29 denote the 29 nonseparable forbidden minors for projective-pl...
متن کاملAlmost-Graphic Matroids
A nongraphic matroid M is said to be almost-graphic if, for all elements e, either M\e or M/e is graphic. We determine completely the class of almost-graphic matroids, thereby answering a question posed by Oxley in his book “Matroid Theory.” A nonregular matroid is said to be almost-regular if, for all elements e, either M\e or M/e is regular. An element e for which both M\e and M/e are regular...
متن کاملQuasi-graphic matroids
Frame matroids and lifted-graphic matroids are two interesting generalizations of graphic matroids. Here we introduce a new generalization, quasi-graphic matroids, that unifies these two existing classes. Unlike frame matroids and lifted-graphic matroids, it is easy to certify that a matroid is quasi-graphic. The main result of the paper is that every 3-connected representable quasi-graphic mat...
متن کاملBranchwidth of graphic matroids
Answering a question of Geelen, Gerards, Robertson and Whittle [2], we prove that the branchwidth of a bridgeless graph is equal to the branchwidth of its cycle matroid. Our proof is based on branch-decompositions
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ژورنال
عنوان ژورنال: Combinatorica
سال: 2018
ISSN: 0209-9683,1439-6912
DOI: 10.1007/s00493-016-3178-3