Resumen de Projective-planar signed graphs and tangled signed graphs

Daniel Slilaty

• A projective-planar signed graph has no two vertex-disjoint negative circles. We prove that every signed graph with no two vertex-disjoint negative circles and no balancing vertex is obtained by taking a projective-planar signed graph or a copy of -K5 and then taking 1-, 2-, and 3-sums with balanced signed graphs.