Fragmenting any Parallelepiped into a Signed Tiling

TL;DR

This paper extends a tiling construction to all parallelepipeds, allowing for signed tiles with positive and negative volumes, and proves a balanced coverage property in space.

Contribution

It generalizes a previous tiling method to include signed tiles for any parallelepiped, removing non-negativity restrictions and establishing a space coverage balance.

Findings

Tiles with positive and negative volumes balance out in space

The construction applies to all parallelepipeds, regardless of sign constraints

The net number of signed tiles remains invariant as points move through space

Abstract

It is broadly known that any parallelepiped tiles space by translating copies of itself along its edges. In earlier work relating to higher-dimensional sandpile groups, the second author discovered a novel construction which fragments the parallelpiped into a collection of smaller tiles. These tiles fill space with the same symmetry as the larger parallelepiped. Their volumes are equal to the components of the multi-row Laplace determinant expansion, so this construction only works when all these signs are non-negative (or non-positive). In this work, we extend the construction to work for all parallelepipeds, without requiring the non-negative condition. This naturally gives tiles with negative volume, which we understand to mean canceling out tiles with positive volume. In fact, with this cancellation, we prove that every point in space is contained in exactly one more tile with positive volume than tile with negative volume. This is a natural definition for a signed tiling. Our main technique is to show that the net number of signed tiles doesn't change as a point moves through space. This is a relatively indirect proof method, and the underlying structure of these tilings remains mysterious.