International audienceGiven four congruent balls A, B, C, D in Rδ that have disjoint interior and admit a line that intersects them in the order ABCD, we show that the distance between the centers of consecutive balls is smaller than the distance between the centers of A and D. This allows us to give a new short proof that n interior-disjoint congruent balls admit at most three geometric permutations, two if n≥7. We also make a conjecture that would imply that n≥4 such balls admit at most two geometric permutations, and show that if the conjecture is false, then there is a counterexample of a highly degenerate nature (in the algebraic sense)
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