On 6d N = (2, 0) theory compactified on a Riemann surface with finite area

We study 6d $$\mathcal {N}=(2,0)$$ theory of type SU(N) compactified on Riemann surfaces with finite area, including spheres with fewer than three punctures. The Higgs branch, whose metric is inversely proportional to the total area of the Riemann surface, is discussed in detail. We show that the zero-area limit, which gives us a genuine 4d theory, can involve a Wigner–İnönü contraction of global symmetries of the six-dimensional theory. We …