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A note on Erdős-Diophantine graphs and Diophantine carpets

Axel Kohnert, Sascha Kurz

math.COarXiv:math/0511705

Abstract

A Diophantine figure is a set of points on the integer grid Z2 where all mutual Euclidean distances are integers. We also speak of Diophantine graphs. In this language a Diophantine figure is a complete Diophantine graph. Due to a famous theorem of Erdős and Anning there are complete Diophantine graphs which are not contained in larger ones. We call them Erdős-Diophantine graphs. A special class of Diophantine graphs are Diophantine carpets. These are planar triangulations of a subset of the integer grid. We give an effective construction for Erdős-Diophantine graphs and characterize the chromatic number of Diophantine carpets.

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