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Events - Page 7

Time and place: , NHA B1120

A tropical curve is a graph embedded in R^2 satisfying a number of conditions. Mikhalkin's celebrated correspondence theorem establishes a correspondence between algebraic curves on a toric surface and tropical curves. This translates the difficult question of counting the number of algebraic curves through a given number of points to the question of counting tropical curves, i.e. certain graphs, with a given notion of multiplicity through a given number of points which can be solved combinatorially.  To get an invariant count, real rational algebraic curves are counted with a sign, the Welschinger sign and there is a real version of the correspondence theorem. Furthermore, Marc Levine defined a generalization of the Welschinger sign that allows to get an invariant count of algebraic curves defined over an arbitrary base field. For this one counts algebraic curves with a certain quadratic form.

In the talk I am presenting work in progress joint with Andrés Jaramillo Puentes in which we provide a version Mikhalkin's correspondence theorem for an arbitrary base field, that is a correspondence between algebraic curves counted with the above mentioned quadratic form and tropical curves counted with a quadratic enrichment of the multiplicity. Then I will explain how to use this quadratic correspondence theorem to do the count of algebraic curves over an arbitrary base field.

Time and place: , NHA B1119
We will discuss the recent theory of Nikulin orbifolds and orbifolds of Nikulin type in dimension 4. Nikulin orbifolds are irreducible holomorphic symplectic orbifolds which are partial resolutions of quotients of IHS manifolds of K3^[n] type. Their deformations are called orbifolds of Nikulin type. Our main aim will be the description of the first known locally complete family of projective irreducible holomorphic symplectic orbifolds of dimension 4 which are of Nikulin type. It is a family of IHS orbifolds that appear as double covers of special complete intersections (3,4) in P^6. This is joint work with Ch. Camere and A. Garbagnati.
Time and place: , NHA107

C*-algebra seminar talk by Lucas Hataishi (University of Oslo)

Time and place: , Erling Sverdrups plass, Niels Henrik Abels hus, 8th floor
Time and place: , NHA B1120

Following Givental, enumerative mirror symmetry can be stated as a relation between genus zero Gromov-Witten invariants and period integrals. I will talk about a relative version of mirror symmetry that relates genus zero relative Gromov-Witten invariants of smooth pairs and relative periods. Then I will talk about how to use it to compute the mirror proper Landau-Ginzburg potentials of smooth log Calabi-Yau pairs.

Time and place: , Abels Utsikt (NHA 1259)
Time and place: , Niels Henrik Abels hus, 9th floor

I will go through my PhD work at DTU. It is about the development of a fully-nonlinear finite difference based potential flow solver which imposes all of the fluid boundaries via an immersed boundary method. The convergence and stability of this approach is first established for various linear and nonlinear wave propagation problems. When it comes to the wave-body interaction problem, cautious attention is paid to the intersection point between free surface and body surface, and a scheme which meets the accuracy and stability requirements best is picked from several proposals. With the scheme introduced in this paper, piston type wave maker and forced heaving cylinder cases with high oscillation frequency have been simulated successfully.

Time and place: , Niels Henrik Abels hus, 9th floor

Internal solitary waves (ISWs) are underwater waves of great amplitude moving horizontally in the layered ocean. The waves induce a velocity field which is felt both at the ocean surface, throughout the entire water column, and at the bottom. When of great amplitude, the waves induce a vortex wake in the bottom boundary layer behind the wave and transport water in the vertical direction displacing, e.g., sediments from the bottom. A fundamental mechanism in the ocean ecosystem is the vertical mixing and movement of particles, e.g., biological materials. In this talk, we present numerical simulations of ISWs of depression and of large amplitude by replicating a laboratory experiment. Furthermore, we discuss the dynamics of ISW-sediment interactions and illustrate particle movements, trajectories, and particle distribution in the water column under the influence of ISWs of large amplitude.

Time and place: , Simula Research Laboratory, Kristian Augusts gate 23 and Zoom - Niels Henrik Abels hus

Doctoral candidate Eleonora Piersanti at the Department of Mathematics will be defending the thesis Parameter-robust formulation and preconditioning of poroelasticity equations for brain modelling for the degree of Philosophiae Doctor.

Time and place: , NHA B1120
Already Plücker knew that a smooth complex plane quartic curve has exactly 28 bitangents. Bitangents of quartic curves are related to a variety of mathematical problems. They appear in one of Arnold's trinities, together with lines in a cubic surface and 120 tritangent planes of a sextic space curve. In this talk, we review known results about counts of bitangents under variation of the ground field. Special focus will be on counting in the tropical world, and its relations to real and arithmetic counts. We end with new results concerning the arithmetic multiplicity of tropical bitangent classes, based on joint work in progress with Sam Payne and Kris Shaw.
Time and place: , Room 1259 "Abels utsikt", 12th floor, Niels Henrik Abels hus, University of Oslo

A two-days meeting of the Steering Council for Centre International de Mathématiques Pures et Appliquées (CIMPA).

Time and place: , NHA107

C*-algebra seminar by Ole Brevig (University of Oslo)

Time and place: , Niels Henrik Abels hus, 9th floor

Why is deep learning so successful in many applications of modern AI? This question has puzzled the AI community for more than a decade, and many attribute the success of deep learning to the implicit regularization imposed by the Neural Network (NN) architectures and the gradient descent algorithm. In this talk we will investigate the implicit regularization of so-called linear NNs in the simplified setting of linear regression. Furthermore, we will show how this theory meets fundamental computational boundaries imposed by the phenomenon of generalized hardness of approximation. That is, the phenomenon where certain optimal NNs can be proven to exist, but any algorithm will fail to compute these NNs to an accuracy below a certain approximation threshold. Thus, paradoxically, there will exist deep learning methods that are provably optimal, but that can only be computed to a certain accuracy.

Vegard Antun is a postdoctoral fellow at the University of Oslo, department of Mathematics.

Time and place: , Abels Utsikt, 12th floor NHA

Boris Odinot, Head of Growth of grasple.com, a non-profit Ed-tech company in the Netherlands, will present about how their platform can be used to help students practice mathematic and statistics, and for teachers to monitor their students' performance.

Time and place: , Abels Utsikt (NHA 1259)
Time and place: , NHA107

QOMBINE seminar by Snorre Bergan (UiO)

Time and place: , Abels Utsikt, 12 etg. Niels Henrik Abels hus

Doctoral candidate Anton Yurchenko-Tytarenko at the Department of Mathematics will be defending the thesis Stochastic Volterra volatility models for the degree of Philosophiae Doctor.

Time and place: , Room 1119, Niels Henrik Abels hus

The Section 4 seminar for the Autumn of 2022 will be held on Thursdays from 10:15–12:00 (see the schedule)

Time and place: , NHA 1020 and Online
Time and place: , Abels Utsikt (NHA 1259)
Time and place: , Erling Sverdrups plass, Niels Henrik Abels hus, 8th floor
Time and place: , NHA B1120

Consider the singularity C^4/(Z/2), where Z/2 acts as the matrix diag(-1,-1,-1,-1). This singularity is special, in that it does not admit a crepant resolution. However, it does admit a so-called noncommutative crepant resolution, given by a Calabi-Yau 4 quiver. The moduli space of representations of this quiver turns out to share a lot of similarities with moduli spaces of sheaves over Calabi-Yau fourfolds, and it turns out that we can reuse techniques from studying moduli of sheaves to define and compute invariants of this moduli space of representations. In this talk, I will explain how these invariants can be defined, and give conjectures about the forms of these invariants. This talk is based on joint work with Raf Bocklandt.

Time and place: , Georg Sverdrups hus, Lecture hall 1

The Thoralf Skolem Memorial Lecture 2022

Time:

This mini-workshop provides young analysts in Norway with an arena to present their research and interact with their peers. 

Time and place: , Erling Sverdrups plass, Niels Henrik Abels hus, 8th floor