Vortex-cluster formula for the baryon number
Let X=R3∪{∞}X=\mathbb{R}^3\cup\{\infty\}X=R3∪{∞} and let U:X→S3U:X\to S^3U:X→S3 be a map of degree BBB. Interpret UUU as two vortices in ψ1\psi_1ψ1 and ψ2\psi_2ψ2 of ψ∈S3\boldsymbol{\psi}\in S^3ψ∈S3, with winding n…