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Thu, 09. Jul at 11:15
Humboldt-Universi...
A posteriori existence verification from nonconforming discretisations
Abstract. A Newton-Kantorovich argument can turn a computed approximation into a certificate for the existence and local uniqueness of a regular solution of a nonlinear PDE. This talk presents such an a posteriori verification framework for nonconforming finite element discretisations with application to a fourth-order formulation for the stationary 2D Navier-Stokes equations. The central difficulty is to obtain a guaranteed lower bound for the continuous inf-sup constant of the linearised operator. We derive such a bound from a discrete inf-sup constant and a novel nonconforming approximation error estimate for linear auxiliary problems.
Thu, 09. Jul at 14:00
Freie Universität...
A completion theorem in genuine G-spectra for profinite G
Fri, 10. Jul at 14:15
FU (T9)
Rare events in particle systems and conservative stochastic PDE
Abstract
Fri, 10. Jul at 14:15
FU (T9)
Fri, 10. Jul at 14:30
1.023
Symplectic quadrics in projective 3-space
Abstract
Fri, 10. Jul at 16:00
1.023
Fukaya categories of conical symplectic resolutions
Abstract
Mon, 13. Jul at 10:00
SR 115, Arnimallee 3
Mon, 13. Jul at 11:30
Weierstrass Lectu...
Metastability for the 2-pattern Hopfield model and general product chains
Abstract. The Hopfield model is a mean-field spin system designed to store a set of patterns as ground states of its Hamiltonian, providing a simple mathematical model of associative memory. At low temperature, the associated Glauber–Metropolis dynamics is metastable: started near a stored pattern, the system remains in its vicinity for an exponentially long time before an abrupt transition towards another pattern. In this talk I discuss the metastable behavior of the model with two stored patterns. After a brief introduction to the potential-theoretic approach to metastability — capacities, equilibrium potentials, and the variational principles that connect them to metastable transition times — I show how the decomposition of the spin sites into the sets where the two patterns agree and disagree reduces the dynamics, via an exact lumping, to a product of two Curie–Weiss-type chains. We will show how this tensorization structure allows metastability to be propagated from the component chains to the full model — capacities of the product chain are controlled by those of its marginals, and one obtains sharp Eyring–Kramers-type estimates for the transition times between the stored patterns. Based on ongoing work with Elena Pulvirenti and Martin Slowik.
Mon, 13. Jul at 13:15
Rudower Chaussee ...
Sparse trigonometric approximation of function classes of mixed smoothness and applications
Tue, 14. Jul at 10:00
WIAS ESH and online
A Proximal Discontinuous Galerkin Method for Total Bounded Variation Based Image Denoising
Tue, 14. Jul at 11:15
1.023 (BMS Room, ...
A remark on Gaiotto's conformal limit correspondence and the geometric Langlands correspondence
Abstract. In this talk, I will illustrate that the Gaiotto correspondence, composed with the Hausel-Thaddeus mirror symmetry, is exactly the same as the oper case of the geometric Langlands correspondence due to Beilinson-Drinfeld. In 2014, Gaiotto conjectured a canonical correspondence between the moduli space of spectral curves for a G-Hitchin system on a curve X and the moduli of G-opers on X, where G is a simple and simply connected complex Lie group. Due to the fact that opers in this context are quantum curves to the topological recursion community, I worked with my collaborators and solved this conjecture (Dumitrescu-Fredrickson-Kydonakis-Mazzeo-Mulase-Neitzke 2016). Of course these moduli spaces are isomorphic. What was new in this work is the construction of a canonical map. When I explained this map to Gaitsgoy at IHES in 2016, he said, "I think I know the map." My talk is a 10-year-too-late report submission to his comment. Indeed, the map comes from the geometric Langlands correspondence!
Tue, 14. Jul at 11:15
1.023 (BMS Room, ...
Tue, 14. Jul at 14:15
WIAS, Erhard-Schm...
Pattern formation and symmetry breaking for a family of functionals and their intrinsic nonlocal curvature
Abstract
Tue, 14. Jul at 14:15
WIAS, Erhard-Schm...
Wed, 15. Jul at 10:00
Weierstrass-Insti...
A Bernstein-von Mises Theorem for indirect measurement models with nonlinear unbounded forward operators
Abstract. Motivated by recently proposed Gaussian process solvers for semilinear elliptic PDEs [1], we consider Bayesian nonparametric inference for indirect measurement models with nonlinear unbounded forward operators. We establish optimal posterior contraction rates and a nonparametric Bernstein-von Mises theorem in strong Sobolev norms (H^{2-d/2}) for d ≤ 3. Our results show that unbounded forward maps may lead to stronger Bernstein-von Mises results in L^p-type norms. This is interesting in light of the conventional statistical wisdom that the nonparametric Bernstein-von Mises phenomenon is only feasible in ‘weak’ metrics. [1] Yifan Chen, Bamdad Hosseini, Houman Owhadi, Andrew M. Stuart. Solving and learning nonlinear PDEs with Gaussian processes, Journal of Computational Physics, 447: 110668 (2021)
Wed, 15. Jul at 11:30
Weierstrass Lectu...
Asymptotic democracy for finite nonlinear Pólya urns
Abstract. In this presentation, we will study Pólya urn models — specifically, a generalization involving an arbitrary finite number of urns and where the addition of a ball to each urn is proportional to a (non-linear) function f of the number of balls already present in that urn. After introducing the continuous-time modeling of this system and presenting two fundamental results regarding monopoly and leadership — more precisely, monopoly (resp. leadership) occurs if and only if $1/f(i)$ (resp. $1/f(i)^2$) is summable —, we will outline a new "democracy" theorem that emerges with weighting functions characterized by relatively slow growth.
Wed, 15. Jul at 14:00
WIAS, Erhard-Schm...
Dynamics of a 3D rimming flow
Abstract
Wed, 15. Jul at 16:00
Thu, 16. Jul at 14:00
Freie Universität...
Fundamental Groups in Algebraic Geometry
Thu, 16. Jul at 16:15
TU Berlin, MA 043
Thu, 16. Jul at 17:15
TU Berlin, MA 043
Wed, 22. Jul at 16:30
IMoS 3003
Operatopes, Operanoids, and Noncommutative zonoids
Wed, 29. Jul at 14:15
WIAS, Erhard-Schm...
Global existence and large time behaviour of nonlinear reaction-diffusion systems
Abstract
Wed, 04. Nov at 14:15
R. 405/405
Thu, 17. Dec at 16:30
EN 058
Drawing algebraic curves in OSCAR
Abstract. I will talk about how to visualize real plane algebraic curves given as the zero set of a polynomial in two variables using Oscar.jl. I will highlight performance and exactness issues using real world examples.