Bessel Potential Spaces and Complex Interpolation: Continuous embeddings

Abstract: Bessel potential spaces, introduced in the 1960s, are derived through complex interpolation between Lebesgue and Sobolev spaces, making them intermediate spaces of fractional differentiability order. Bessel potential spaces have recently gained attention due to their identification with the Riesz fractional gradient. This paper explores Bessel potential spaces as complex interpolation spaces, providing original proofs of fundamental properties based on abstract interpolation theory. Main results include a direct proof of norm equivalence, continuous embeddings, and the relationship with Gagliardo spaces.