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math.AG2025
Kleinian orbifolds, Cohomological Hall Algebras, and Yangians
Francesco Sala, Olivier Schiffmann, Parth Shimpi
We establish, for each orbifold crepantly resolving a Kleinian singularity, the existence of the cohomological Hall algebra (COHA) of coherent sheaves supported on the exceptional…
math.AG2025
Simple complexes on a flopped curve
Parth Shimpi
Studying crepant blow-ups of (compound) du Val singularities, we classify complexes of coherent sheaves which admit no negative self-extensions -- such a complex, up to flops and m…
math.AG2025
Torsion pairs and 3-fold flops
Parth Shimpi
This paper classifies t-structures on the local derived category of a 3-fold flopping contraction, that are intermediate with respect to the heart of perverse coherent sheaves. Equ…