It is known that there are normal plane maps M5 with minimum degree 5 such that the minimum degree-sum w(S5) of 5-stars at 5-vertices is arbitrarily large. In 1940, Lebesgue showed that if an M5 has no 4-stars of cyclic type (5, 6, 6, 5) centered at 5-vertices, then w(S5) ≤ 68. We improve this bound of 68 to 55 and give a construction of a (5, 6, 6, 5)-free M5 with w(S5) = 48
@article{bwmeta1.element.doi-10_7151_dmgt_1748, author = {Oleg V. Borodin and Anna O. Ivanova and Tommy R. Jensen}, title = {5-Stars of Low Weight in Normal Plane Maps with Minimum Degree 5}, journal = {Discussiones Mathematicae Graph Theory}, volume = {34}, year = {2014}, pages = {539-546}, zbl = {1310.05063}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.doi-10_7151_dmgt_1748} }
Oleg V. Borodin; Anna O. Ivanova; Tommy R. Jensen. 5-Stars of Low Weight in Normal Plane Maps with Minimum Degree 5. Discussiones Mathematicae Graph Theory, Tome 34 (2014) pp. 539-546. http://gdmltest.u-ga.fr/item/bwmeta1.element.doi-10_7151_dmgt_1748/
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