For suitable finite groups G, we construct contractible 4-manifolds C with an
effective G-action on ∂C whose associated pairs (C,g) for all g∈G are distinct smoothings of the pair (C,∂C). Indeed C embeds in a
4-manifold so that cutting out C and regluing using distinct elements of G
yield distinct smooth 4-manifolds.Comment: 9 pages, 3 figure