Tidligere gjesteforelesninger og seminarer - Side 47
Enrico Fermi and the birth of modern nonlinear physics
In the early fifties in Los Alamos E. Fermi in collaboration with J. Pasta and S. Ulam investigated a one dimensional chain of equal masses connected by a weakly nonlinear spring. The key question was related to the understanding of the phenomenon of conduction in solids; in particular they wanted to estimate the time needed to reach a statistical equilibrium state characterized by the equipartition of energy among the Fourier modes. They approached the problem numerically using the MANIAC I computer; however, the system did not thermailize and they observed a recurrence to the initial state (this is known as the FPU-recurrence). This unexpected result has led to the development of the modern nonlinear physics (discovery of solitons and integrability). In this seminar, I will give an historical overview of the subject and present the different approaches that have been proposed in the last 60 years for explaining this paradox. Very recent results on the estimation of the time scale and on the explanation of the mechanism of equipartition will also be discussed.
In Part 2 we will delve into the worlds of derived and spectral algebraic
geometry. After reviewing some basic notions we will explain how motivic
homotopy theory can be extended to these settings. As far as time permits
we will then discuss applications to virtual fundamental classes, as well
as a new cohomology theory for commutative ring spectra, a brave new
analogue of Weibel's KH
In Part 2 we will delve into the worlds of derived and spectral algebraic
geometry. After reviewing some basic notions we will explain how motivic
homotopy theory can be extended to these settings. As far as time permits
we will then discuss applications to virtual fundamental classes, as well
as a new cohomology theory for commutative ring spectra, a brave new
analogue of Weibel's KH
Dagmar Frisch, Marie Skłodowska-Curie Research Fellow, University of Birmingham
We consider extensions of Morel-Voevodsky's motivic homotopy theory to the
settings of derived and spectral algebraic geometry. Part I will be a
review of the language of infinity-categories and the setup of
Morel-Voevodsky homotopy theory in this language. As an example we will
sketch an infinity-categorical proof of the representability of Weibel's
homotopy invariant K-theory in the motivic homotopy category.
Numerical methods for stochastic conservation laws
Friday seminar by Marcin Piwczyński from Nicolaus Copernicus University in Toruń, Poland
Nick Kaiser, IfA, Hawai University
Experimental investigation of linear stability mechanisms in stratified gas-liquid pipe flow
The evolution of interfacial waves on a stratified air water pipe flow is investigated experimentally. An oscillating plate introduced controlled perturbations at the inlet of the pipe. High speed cameras captured the evolution of these perturbations along the pipe by means of a phase-locked shadowgraphy technique. Thereby, it was possible to measure the temporal and the spatial evolution of the disturbances introduced in the flow. Particle image velocimetry was performed further downstream in order to evaluate changes in the base flow.
A relatively large data bank has been gathered with varying air and water flow rates as well as varying amplitudes and frequencies of the inlet perturbations. Some preliminary results contain a qualitative assessment of linear vs. non-linear regimes and momentum transfer into the water layer.
Professor Eric Priest, St Andrews University, Scotland:
Our Dynamic Sun
Yuan Wang (Utah), gives the Seminar in Algebra and Algebraic Geometry:
"On the characterization of abelian varieties for log pairs in zero and positive characteristic"
Eric Priest, University of St.Andrews
Håvard Kvamme (UiO, Dept. of mathematics) will give a seminar in the lunch area, 8th floor Niels Henrik Abels hus at 14:15.
We will discuss the motivic May spectral sequence and demonstrate how to use it to identify Massey products in the motivic Adams spectral sequence. We will then investigate what is known about the motivic homotopy groups of the eta-local sphere over the complex numbers and discuss how these calculations may work over other base fields.
Jack Carlyle, ITA, Postdoc
Francesco Galuppi (UiO/Ferrara) gives the algebraic geometry seminar:
"Identifiability of polynomials and Cremona transformations."
Alfredo Galindo-Uribarri, Oak Ridge National Laboratory / University of Tennessee, Knoxville.
Certain 3-dimensional lens spaces are known to smoothly bound 4-manifolds with the rational homology of a ball. These can sometimes be useful in cut-and-paste constructions of interesting (exotic) smooth 4-manifolds. To this end it is interesting to identify 4-manifolds which contain these rational balls. Khodorovskiy used Kirby calculus to exhibit embeddings of rational balls in certain linear plumbed 4-manifolds, and recently Park-Park-Shin used methods from the minimal model program in 3-dimensional complex algebraic geometry to generalise Khodorovskiy's result. The goal of this talk is to give an accessible introduction to the objects mentioned above and also to describe a much easier topological proof of Park-Park-Shin's theorem.
Bartosz Kwasniewski (Odense) will give a talk with title: Paradoxicality and pure infiniteness of C*-algebras associated to Fell bundles
Abstract: Abstract: In this talk we present conditions implying pure infiniteness of the reduced cross-sectional $C^*$-algebra $C^*_r(\mathcal{B})$ of a Fell bundle $\mathcal{B}$ over a discrete group $G$. We introduce notions of aperiodicity, $\mathcal{B}$-paradoxicality and residual $\mathcal{B}$-infiniteness. We discuss their relationship with similar conditions studied, in the context of crossed products, by the following duos: Laca, Spielberg; Jolissaint, Robertson; Sierakowski, R{\o}rdam; Giordano, Sierakowski and Kirchberg, Sierakowski. (based on joint work with Wojciech Szyma{\'n}ski)
Francesca Biagini, professor in mathematical finance from Ludwig-Maximillian University of Munich, will give an intensive course from Tuesday Sept 13 to Friday Sept 16.
Ata karakci, Postdoctoral Researcher , ITA
Seckin Adali (UiO), gives the Seminar in Algebra and Algebraic Geometry:
Singularities of Restriction Varieties in OG(k,n)
In the nineties, Deninger gave a detailed description of a conjectural cohomological interpretation of the (completed) Hasse-Weil zeta function of a regular scheme proper over the ring of rational integers. He envisioned the cohomology theory to take values in countably infinite dimensional complex vector spaces and the zeta function to emerge as the regularized determinant of the infinitesimal generator of a Frobenius flow. In this talk, I will explain that for a scheme smooth and proper over a finite field, the desired cohomology theory naturally appears from the Tate cohomology of the action by the circle group on the topological Hochschild homology of the scheme in question.
Abstract: Exploring connections between subfactors and conformal field theories, Vaughan Jones recently observed that planar algebras give rise to unitary representations of the Thompson group F, and more generally, to unitary representations of the group of fractions of certain categories. Remarkably, this procedure applies to oriented link invariants. In particular, a suitably normalized HOMFLYPT polynomial is a positive definite function on the oriented Thompson group. (Based on joint work with V. Aiello and V. Jones.)