(more unsolved problems in mathematics) In geometric graph theory, the Hadwiger–Nelson problem, named after Hugo Hadwiger and Edward Nelson, asks for the...

are necessary to contain the original Hadwiger's conjecture on dissection into orthoschemes Hadwiger–Nelson problem on the chromatic number of unit distance...

from the utility graph K3,3 by subdividing one of its edges. The Hadwiger–Nelson problem asks how many colors are needed to color the points of the Euclidean...

contributed to the study of the Hadwiger–Nelson problem in geometric graph theory, making the first progress on the problem in over 60 years. De Grey is...

Grötzsch's theorem: triangle-free planar graphs are 3-colorable. Hadwiger–Nelson problem: how many colors are needed to color the plane so that no two points...

like the simpler Moser spindle, it provides a lower bound for the Hadwiger–Nelson problem: coloring the points of the Euclidean plane so that each unit line...

with a forbidden induced tree The Hadwiger conjecture relating coloring to clique minors The Hadwiger–Nelson problem on the chromatic number of unit distance...

problem, also now known as the Hadwiger–Nelson problem, was a favorite of Paul Erdős, who mentioned it frequently in his problems lectures. In 2018, Aubrey...

proven in the plane, but remains open in higher dimensions. The Hadwiger–Nelson problem concerns the minimum number of colors needed to color the points...

development of these areas, concentrating in particular on the Hadwiger–Nelson problem and on the biography of Bartel Leendert van der Waerden. It was...