Abstract
For each integer $d\geqslant 3$, we obtain a characterization of all graphs in which the ball of radius $3$ around each vertex is isomorphic to the ball of radius 3 in $\mathbb{L}^{d}$, the graph of the $d$-dimensional integer lattice. The finite, connected graphs with this property have a highly rigid, ‘global’ algebraic structure; they can be viewed as quotient lattices of $\mathbb{L}^{d}$ in various compact $d$-dimensional orbifolds which arise from crystallographic groups. We give examples showing that ‘radius 3’ cannot be replaced by ‘radius 2’, and that ‘orbifold’ cannot be replaced by ‘manifold’. In the $d=2$ case, our methods yield new proofs of structure theorems of Thomassen [‘Tilings of the Torus and Klein bottle and vertex-transitive graphs on a fixed surface’, Trans. Amer. Math. Soc.323 (1991), 605–635] and of Márquez et al. [‘Locally grid graphs: classification and Tutte uniqueness’, Discrete Math.266 (2003), 327–352], and also yield short, ‘algebraic’ restatements of these theorems. Our proofs use a mixture of techniques and results from combinatorics, geometry and group theory.
Highlights
Many results in Combinatorics concern the impact of ‘local’ properties on ‘global’ properties of combinatorial structures
Conclusion and related problems Theorem 1 states that a connected graph G which is weakly 3-locally Ld is normally covered by Ld
Our results imply that if r r ∗(d), a connected graph which is r -locally Ld is covered by Ld, where
Summary
Many results in Combinatorics concern the impact of ‘local’ properties on ‘global’ properties of combinatorial structures (for example graphs). A natural ‘local’ condition to impose on a graph, is that it be regular. If d ∈ N, a graph is said to be d-regular if all its vertices have degree d. Regular graphs have been extensively studied, and satisfy some rather strong ‘global’ properties. A wellknown conjecture of Nash-Williams states that if G is an n-vertex, d-regular graph c The Author(s) 2016.
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