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  • Fusion Category Symmetries in Quantum Field Theory

    Speaker: Yifan Wang (NYU) Title: Fusion Category Symmetries in Quantum Field Theory Abstract: Topological defects provide a modern perspective on symmetries in quantum field theory. They generalize the familiar inverti https://www.youtube.com/watch?v=p82wzcicCk8&t=72s ble symmetries described by groups to non-invertible symmetries described by fusion categories. Such generalized symmetries are ubiquitous in quantum field theory and provide new constraints on […]

  • The stability of charged black holes

    Abstract: Black holes solutions in General Relativity are parametrized by their mass, spin and charge. In this talk, I will motivate why the charge of black holes adds interesting dynamics to solutions of the Einstein equation thanks to the interaction between gravitational and electromagnetic radiation. Such radiations are solutions of a system of coupled wave equations […]

  • CMSA-Interdisciplinary-Science-Seminar-11.04.21-1583x2048-1

    11/4/21 CMSA Interdisciplinary Science Seminar

    Title: Exploring Invertibility in Image Processing and Restoration Abstract: Today’s smartphones have enabled numerous stunning visual effects from denoising to beautification, and we can share high-quality JPEG images easily on the internet, but it is still valuable for photographers and researchers to keep the original raw camera data for further post-processing (e.g., retouching) and analysis. However, the […]

  • The Greene-Plesser Construction Revisited

    Member Seminar Speaker: Chuck Doran Title: The Greene-Plesser Construction Revisited Abstract: The first known construction of mirror pairs of Calabi-Yau manifolds was the Greene-Plesser “quotient and resolve” procedure which applies to pencils of hypersurfaces in projective space. We’ll review this approach, uncover the hints it gives for some more general mirror constructions, and describe a brand-new variant […]

  • Cosection localization for virtual fundamental classes of d-manifolds and Donaldson-Thomas invariants of Calabi-Yau fourfolds

    Abstract: Localization by cosection, first introduced by Kiem-Li in 2010, is one of the fundamental techniques used to study invariants in complex enumerative geometry. Donaldson-Thomas (DT) invariants counting sheaves on Calabi-Yau fourfolds were first defined by Borisov-Joyce in 2015 by combining derived algebraic and differential geometry. In this talk, we develop the theory of cosection localization […]

  • Cosection localization for virtual fundamental classes of d-manifolds and Donaldson-Thomas invariants of Calabi-Yau fourfolds

    Speaker: Michail Savvas, UT Austin Title: Cosection localization for virtual fundamental classes of d-manifolds and Donaldson-Thomas invariants of Calabi-Yau fourfolds Abstract: Localization by cosection, first introduced by Kiem-Li in 2010, is one of the fundamental techniques used to study invariants in complex enumerative geometry. Donaldson-Thomas (DT) invariants counting sheaves on Calabi-Yau fourfolds were first defined by Borisov-Joyce […]

  • Hypergraph decompositions and their applications

    Speaker: Peter Keevash, Oxford Title: Hypergraph decompositions and their applications Abstract: Many combinatorial objects can be thought of as a hypergraph decomposition, i.e. a partition of (the edge set of) one hypergraph into (the edge sets of) copies of some other hypergraphs. For example, a Steiner Triple System is equivalent to a decomposition of a complete graph […]

  • 20211110_Richard-Thomas_poster

    Higher rank DT theory from rank 1

    Abstract: Fix a Calabi-Yau 3-fold X. Its DT invariants count stable bundles and sheaves on X. The generalised DT invariants of Joyce-Song count semistable bundles and sheaves on X. I will describe work with Soheyla Feyzbakhsh showing these generalised DT invariants in any rank r can be written in terms of rank 1 invariants. By the […]

  • Sharp decay for Teukolsky equation in Kerr spacetimes

    Abstract: Teukolsky equation in Kerr spacetimes governs the dynamics of the spin $s$ components, $s=0, \pm 1, \pm 2$ corresponding to the scalar field, the Maxwell field, and the linearized gravity, respectively. I will discuss recent joint work with L. Zhang on proving the precise asymptotic profiles for these spin $s$ components in Schwarzschild and […]

  • Nonreciprocal matter: living chiral crystals

    Abstract: Active crystals are highly ordered structures that emerge from the nonequilibrium self-organization of motile objects, and have been widely studied in synthetic and bacterial active matter. In this talk, I will describe how swimming sea star embryos spontaneously assemble into chiral crystals that span thousands of spinning organisms and persist for tens of hours. Combining […]

  • CMSA-Interdisciplinary-Science-Seminar-11.11.21

    11/11/21 Interdisciplinary Science Seminar

    Title: The Kervaire conjecture and the minimal complexity of surfaces Abstract: We use topological methods to solve special cases of a fundamental problem in group theory, the Kervaire conjecture. The conjecture asserts that, for any nontrivial group G and any element w in the free product G*Z, the quotient (G*Z)/<<w>> is still nontrivial. We interpret this […]

  • Universal relations between entanglement, symmetries, and entropy

    Member Seminar Speaker: Gabriel Wong  Title: Universal relations between entanglement, symmetries, and entropy Abstract: Entanglement is an essential property of quantum systems that distinguishes them from classical ones.   It is responsible for the nonlocal character of quantum information and provides a resource for quantum teleportation and quantum computation. In this talk I will provide an introduction […]