3 papers
math.AG2026
A Hopf index for isotropic sections of orthogonal bundles
Martijn Kool, Jeongseok Oh, Jørgen Vold Rennemo +1
The Hopf index equates the multiplicity of a zero of a section of a vector bundle with a winding number. We give eight analogues for isotropic sections of bundles with quadratic fo…
math.AG2025
Proof of a magnificent conjecture
M. Kool, J. V. Rennemo
Motivated by super-Yang-Mills theory on a Calabi-Yau 4-fold, Nekrasov and Piazzalunga have assigned weights to -tuples of solid partitions and conjectured a formula for their we…
math.AG2025
Factorisability in K-theory
Jørgen Vold Rennemo
We revisit and give a detailed proof of a lemma of Okounkov showing that, for a scheme X with a torus action, the Euler characteristic generating function associated with a "factor…