Mixing these two modes using Eq. 1.13 gives: and in a similar way to AB2, the AB4 T-4 E-mode ℳ(𝒒 1 , 𝒒 2 ) is periodic in 𝜃. This property allows for an injective mapping of the space by limiting 𝜃 ∈ [0, 𝜋). This is a compactification to a sphere (ℝ 2 → 𝑆 2 ) yielding the 𝒞 4E space as shown in Fig. . A detailed analysis of this space is given elsewhere .