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1:00pm to 2:00pm - Zoom / RH306 - Dynamical Systems Sergey Tikhomirov - (Pontifícia Universidade Católica do Rio de Janeiro) Dynamics on Banach spaces: Hyperbolicity, shadowing, stability We introduce a notion of generalized $(C, \lambda)$-structure for nonlinear diffeomorphisms of Banach spaces. The main differences to the classical notion of hyperbolicity are that we allow the hyperbolic splitting to be discontinuous and in invariance condition assume only inclusions instead of equalities for both stable and unstable subspace. These aspects allow us to cover Morse-Smale systems and generalized hyperbolicity. We suggest that the generalized $(C, \lambda)$-structure for infinite-dimensional dynamics plays a role similar to ``Axiom A and strong transversality condition'' for dynamics on compact manifolds. For diffeomorphisms of reflexive Banach space we showed that generalized $(C, \lambda)$-structure implies Lipschitz (periodic) shadowing and is robust under $C^1$-small perturbations. Assuming that generalized $(C, \lambda)$-structure is continuous for diffeomorphisms of arbitrary Banach spaces we obtain a weak form of structural stability: the diffeomorphism is semiconjugated from both sides with any $C^1$-small perturbation. |
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1:00pm - RH 340N - Algebraic Geometry Artan Sheshmani - (Beijing Institute for Mathematical Sciences and Applications (BIMSA)) Counting Curves and Surfaces in Calabi-Yau Threefolds and Modular Forms I will discuss a famous 40-year-old conjecture from string theory known as the S-duality modularity conjecture. It predicts that a certain partition function encoding the count of stable solutions to the partial differential equations describing D-brane interactions, supported on complex surfaces deforming inside a Calabi-Yau threefolds is given by a modular form. Depending on how these surfaces deform in the ambient Calabi-Yau threefold, one obtains different counting problems and correspondingly different versions of the S-duality conjecture. I will explain an algebro-geometric reformulation of this problem and survey a series of results obtained with collaborators over the past 15 years toward proving the conjecture in various geometric settings. Finally, I will describe ongoing work on the most difficult version of the conjecture, which involves tools such as Tyurin degeneration, derived intersection theory, and the categorification of Donaldson-Thomas invariants. |
