Capsule
A capsule is defined as
$$\mathcal{C} := \mathcal{L} \oplus \mathcal{S}, \quad \mathcal{L} := \{ c + g\alpha \, | \, \alpha \in
[-1,1] \}, \quad \mathcal{S} = \{ x \, | \, ||x||_2 \leq r \}. $$
Capsules are compact, convex, and bounded sets. More information in Section 2.2.1.7 in the CORA manual.