Homological Mirror Symmetry - Main Theorem
Kontsevich's homological mirror symmetry conjecture has been proven in several important cases, establishing categorical equivalences that underpin our understanding of mirror symmetry. These theorems provide rigorous foundations for the physical predictions.
Let be an elliptic curve and its dual. There exists a triangulated equivalence:
The equivalence is constructed explicitly by:
- Sending line bundles to Lagrangian tori
- Sending skyscraper sheaves to Lagrangian circles
- Verifying Ext groups match Floer cohomology
This was the first rigorous proof of HMS and established the feasibility of the categorical approach.
The proof uses the fact that both sides can be described explicitly: coherent sheaves on are classified by degree and indecomposables, while Lagrangian submanifolds in are circles and tori.
For a smooth quartic K3 surface and its mirror :
The proof constructs the equivalence using:
- Spherical objects and spherical twists
- Lefschetz fibrations and vanishing cycles
- Symplectic topology techniques
This extended HMS beyond tori to higher-dimensional Calabi-Yau manifolds.
Let and be smooth projective varieties. Every fully faithful exact functor:
is representable by a Fourier-Mukai kernel :
This provides a framework for understanding derived equivalences algebraically.
Orlov's theorem implies that HMS equivalences on the B-side are always Fourier-Mukai. The challenge is constructing the corresponding Fukaya-Mukai kernels on the A-side.
For a smooth toric Fano variety and its Landau-Ginzburg mirror :
where is the Fukaya-Seidel category of the Landau-Ginzburg model.
Objects on the right are Lagrangian thimbles (vanishing cycles) associated to critical points of .
This theorem establishes HMS in the toric setting and connects to homological algebra of matrix factorizations, providing computational tools for both sides.
The derived category for a smooth projective variety is generated as a triangulated category by any spanning class, i.e., a collection such that:
For HMS, proving the Fukaya category is generated by specific Lagrangians reduces the conjecture to verifying Ext/Floer isomorphisms for generators.
These theorems provide the mathematical foundation for homological mirror symmetry and demonstrate its feasibility across various geometric contexts.