Instantons on flat space: Explicit constructions

In this note, we revisit some well-known examples of instantons on flat space that were originally discovered in the physics literature. In particular, we explain how the basic instanton on $\mathbb{R}^4$, with its flat hyperkaehler structure, has natural generalisations to $\mathbb{R}^7$ and $\mathbb{R}^8$ viewed as flat $G_2$- and Spin(7)-manifolds, respectively. We also provide the details of an arguably less known construction of ASD instantons on $\mathbb{H}^n$, in the sense of quaternionic geometry.