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Published online by Cambridge University Press: 24 October 2008
Let M and Q be closed manifolds, and write ℝ+ = [0, ∞). Our main result is that, in both the PL and topological categories, M × ℝ+ unknots in Q × ℝ+ in codimension ≥ 3 (see Theorem 1 for a precise statement). The proof is essentially a generalization of Stallings's topological unknotting of spheres(13), the main tool being engulfing.