Compact embeddings of Brezis-Wainger type

Abstract

Let Ω be a bounded domain in Rn and denote by idΩ the restriction operator from the Besov space B1+n/p pq (Rn) into the generalized Lipschitz space Lip(1,−α)(Ω). We study the sequence of entropy numbers of this operator and prove that, up to logarithmic factors, it behaves asymptotically like ek(idΩ) ∼ k−1/p if α > max (1 + 2/p −1/q, 1/p). Our estimates improve previous results by Edmunds and Haroske.