01
Derived categories and semiorthogonal decompositions of Fano varieties
Exceptional collections, semiorthogonal decompositions and mutations provide powerful tools to understand derived categories of coherent sheaves and categorical resolutions of singularities, and to investigate the geometric information that they carry. The derived category is a very rigid invariant for a Fano variety, but the choice of an appropriate subcategory can lead to the construction of more subtle birational invariants. This approach can be extended to singular varieties by constructing semiorthogonal decompositions of the categorical resolution of singularities.
02
Birational equivalences, K-equivalence, and the DK conjecture
While the derived category is known to be an invariant up to isomorphism for smooth Fano and general type varieties, its behavior as a birational invariant in broader settings (e.g. flops and related constructions) remains the subject of open conjectures. In particular, there is substantial evidence suggesting that certain birational transformations, known as K-equivalences, should induce equivalences at the level of derived categories.
03
Gauged linear sigma models, phase transitions, and mathematical physics
In physics, gauged linear sigma models are supersymmetric gauge theories that exhibit multiple phases. Unlike the original abelian models, non-abelian GLSMs can have several “geometric” phases, each corresponding to the geometry of a smooth projective variety. Conjecturally, the physical relationship between these phases is reflected mathematically by Fourier–Mukai functors inducing equivalences, or embeddings, between the derived categories of the associated varieties.
04
Varieties with two projective bundle structures
The classification of simple K-equivalences, i.e. crepant birational maps between smooth projective varieties which admit a common resolution whose morphism to either side is a single blowup along a smooth center, is closely related to the classification of special Fano varieties called roofs. These are varieties of Picard rank two, whose extremal contractions are projective bundles, and such that there is a line bundle which restricts to O(1) on the fibers of both contractions. Although the roof condition is rather restrictive, the classification is still an open problem.