We consider three graphs, \(G_{7,3}\), \(G_{7,4}\), and \(G_{7,6}\), related to Keller’s conjecture in dimension 7. The conjecture is false for this dimension if and only if at least one of the graphs contains a clique of size \(2^7 = 128\). We present an automated method to solve this conjecture by encoding the existence of such a clique as a propositional formula. We apply satisfiability solving combined with symmetry-breaking techniques to determine that no such clique exists. This result implies that every unit cube tiling of \(\mathbb {R}^7\) contains a facesharing pair of cubes. Since a faceshare-free unit cube tiling of \(\mathbb {R}^8\) exists (which we also verify), this completely resolves Keller’s conjecture.
This is a (ultimately equivalent) variant of a definition of Kisielewicz and Łysakowska [15‐17]. They defined for \(x \in \mathbb {R}^d\) and \(i \in [d]\), L(T, x, i) to be the set of all \(i^{\text {th}}\) coordinates \(t_i\) of vectors \(t \in T\) such that \(([0,1)^d + t) \cap ([0,1]^d + x) \ne \emptyset \) and \(t_i \le x_i\). A tiling is s-discrete if and only if \(L(T, x, i) \le s\) for all x and i.