Abstract. We introduce weak slice conditions and investigate imbeddings of Sobolev spaces in various Lipschitz-type spaces.
IntroductionBojarski [B] proved that Sobolev-Poincaré imbeddings are valid on all John domains; see also [Mto]. In [BK1], it is shown that John domains are essentially the right class for this imbedding, since a bounded domain G ⊂ R n is a John domain if and only if it supports a Sobolev-Poincaré imbedding and satisfies a certain separation condition. Corresponding results for the p = n (Trudinger) and p > n (Hölder) cases of the Sobolev Imbedding Theorem are given in [BK2], where it is shown that for domains satisfying a certain slice condition, each of these imbeddings is equivalent to a mean cigar condition dependent on p; see Section 1 for definitions of these concepts. For other results on Hölder imbeddings, we refer the reader to [A], [Mz], and [KR].In one way, the results of [BK2] are less satisfying than those of [BK1]. In [BK1], the strong geometric condition (John) is equivalent to the combination of the weak geometric condition (separation) and a Sobolev-Poincaré imbedding. However in [BK2], the weak geometric condition (slice) is not implied by the strong geometric condition (mean cigar) for any value of p ≥ n. For p = n, Buckley and O'Shea [BO] overcame this deficiency by showing that the strong geometric condition is equivalent to the combination of a so-called weak slice condition (which is implied by a slice condition) and the Trudinger imbedding. Here we prove the following analogous result for p > n; the terminology is explained in Sections 1 and 2.