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math.AG2025
Cones of Noether-Lefschetz divisors and moduli spaces of hyperkähler manifolds
Ignacio Barros, Pietro Beri, Laure Flapan +1
We give a general formula for generators of the NL-cone, the cone of effective linear combinations of irreducible components of Noether-Lefschetz divisors, on an orthogonal modular…
math.AG2025
Quasi-modular forms for the orthogonal group and Gromov-Witten theory of Enriques surfaces
Georg Oberdieck, Brandon Williams
We develop the theory of almost-holomorphic and quasimodular forms for orthogonal groups of a lattice of signature through orthogonal lowering and raising operators. The in…
math.AG2025
K3 Surfaces and Orthogonal Modular Forms
Adrian Clingher, Andreas Malmendier, Brandon Williams
We determine explicit generators for the ring of modular forms associated with the moduli spaces of K3 surfaces with automorphism group and of Picard r…