Abstract
We construct finite groups whose Cayley graphs have large girth even with respect to a discounted distance measure that contracts arbitrarily long sequences of edges from the same color class (subgroup), and only counts transitions between color classes (cosets). These groups are shown to be useful in the construction of finite bisimilar hypergraph covers that avoid any small cyclic configurations. We present two applications to the finite model theory of the guarded fragment: a strengthening of the known finite model property for GF and the characterization of GF as the guarded bisimulation invariant fragment of first-order logic in the sense of finite model theory.
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Index Terms
- Highly acyclic groups, hypergraph covers, and the guarded fragment
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