Lifts of matroid representations over partial fields
Abstract
There exist several theorems which state that when a matroid is representable over distinct fields F_1,...,F_k, it is also representable over other fields. We prove a theorem, the Lift Theorem, that implies many of these results. First, parts of Whittle's characterization of representations of ternary matroids follow from our theorem. Second, we prove the following theorem by Vertigan: if a matroid is representable over both GF(4) and GF(5), then it is representable over the real numbers by a matrix such that the absolute value of the determinant of every nonsingular square submatrix is a power of the golden ratio. Third, we give a characterization of the 3-connected matroids having at least two inequivalent representations over GF(5). We show that these are representable over the complex numbers. Additionally we provide an algebraic construction that, for any set of fields F_1,...,F_k, gives the best possible result that can be proven using the Lift Theorem.
Cite
@article{arxiv.0804.3263,
title = {Lifts of matroid representations over partial fields},
author = {R. A. Pendavingh and S. H. M. van Zwam},
journal= {arXiv preprint arXiv:0804.3263},
year = {2011}
}
Comments
41 pages, 1 figure. Contains minor revisions, the most substantial being a new Section 4.1 that shows how Tutte's characterization of regular matroids follows from our theorem, a new proof of Theorem 5.1 (a partial field can be embedded in a ring), and a new appendix listing partial fields. Submitted to Journal of Combinatorial Theory, Series B