文摘
Let G be a plane graph and T an even subset of its vertices. It has been conjectured that if all T-cuts of G have the same parity and the size of every T-cut is at least k, then G contains k edge-disjoint T -joins. The case class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0095895615001094&_mathId=si1.gif&_user=111111111&_pii=S0095895615001094&_rdoc=1&_issn=00958956&md5=c3a117ad8c89dd20a4c79858c985b8df" title="Click to view the MathML source">k=3class="mathContainer hidden">class="mathCode"> is equivalent to the Four Color Theorem, and the cases class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0095895615001094&_mathId=si2.gif&_user=111111111&_pii=S0095895615001094&_rdoc=1&_issn=00958956&md5=60aeac8e54dce04c365284a66369d726" title="Click to view the MathML source">k=4class="mathContainer hidden">class="mathCode">, which was conjectured by Seymour, and class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0095895615001094&_mathId=si3.gif&_user=111111111&_pii=S0095895615001094&_rdoc=1&_issn=00958956&md5=2d08a9893c43fee0f4cebcd2b1a0eb13" title="Click to view the MathML source">k=5class="mathContainer hidden">class="mathCode"> were proved by Guenin. We settle the next open case class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0095895615001094&_mathId=si4.gif&_user=111111111&_pii=S0095895615001094&_rdoc=1&_issn=00958956&md5=0936a704f7b111517864dd40e31a1ebd" title="Click to view the MathML source">k=6class="mathContainer hidden">class="mathCode">.