We give two graph theoretical characterizations of tope graphs of (complexesof) oriented matroids. The first is in terms of excluded partial cube minors,the second is that all antipodal subgraphs are gated. A direct consequence is athird characterization in terms of zone graphs of tope graphs. Further corollaries include a characterization of topes of oriented matroidsdue to da Silva, another one of Handa, a characterization of lopsided systemsdue to Lawrence, and an intrinsic characterization of tope graphs of affineoriented matroids. Furthermore, we obtain polynomial time recognitionalgorithms for tope graphs of the above and a finite list of excluded partialcube minors for the bounded rank case. In particular, this answers a relativelylong-standing open question in oriented matroids.
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