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Conformal blocks for Galois covers of algebraic curves. (English) Zbl 1537.17041

Summary: We study the spaces of twisted conformal blocks attached to a \(\Gamma\)-curve \(\Sigma\) with marked \(\Gamma\)-orbits and an action of \(\Gamma\) on a simple Lie algebra \(\mathfrak{g}\), where \(\Gamma\) is a finite group. We prove that if \(\Gamma\) stabilizes a Borel subalgebra of \(\mathfrak{g}\), then the propagation theorem and factorization theorem hold. We endow a flat projective connection on the sheaf of twisted conformal blocks attached to a smooth family of pointed \(\Gamma\)-curves; in particular, it is locally free. We also prove that the sheaf of twisted conformal blocks on the stable compactification of Hurwitz stack is locally free. Let \(\mathscr{G}\) be the parahoric Bruhat-Tits group scheme on the quotient curve \(\Sigma /\Gamma\) obtained via the \(\Gamma\)-invariance of Weil restriction associated to \(\Sigma\) and the simply connected simple algebraic group \(G\) with Lie algebra \(\mathfrak{g}\). We prove that the space of twisted conformal blocks can be identified with the space of generalized theta functions on the moduli stack of quasi-parabolic \(\mathscr{G}\)-torsors on \(\Sigma /\Gamma\) when the level \(c\) is divisible by \(|\Gamma |\) (establishing a conjecture due to Pappas and Rapoport).

MSC:

17B67 Kac-Moody (super)algebras; extended affine Lie algebras; toroidal Lie algebras
17B68 Virasoro and related algebras
14H81 Relationships between algebraic curves and physics
17B81 Applications of Lie (super)algebras to physics, etc.
14D21 Applications of vector bundles and moduli spaces in mathematical physics (twistor theory, instantons, quantum field theory)
14H60 Vector bundles on curves and their moduli
81R10 Infinite-dimensional groups and algebras motivated by physics, including Virasoro, Kac-Moody, \(W\)-algebras and other current algebras and their representations

Software:

MathOverflow

References:

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