Martingale Hardy-Amalgam Spaces: Atomic decompositions and duality

In this paper, we introduce the notion of martingale Hardy-amalgam spaces: $H^s_{p,q},\,\,\mathcal{Q}_{p,q}$ and $\mathcal{P}_{p,q}$. We present two atomic decompositions for these spaces. The dual space of $H^s_{p,q}$ for $0<p\le q\le 1$ is shown to be a Campanato-type space.