Tidligere arrangementer - Side 96

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 Sk?odowska-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.

ESOP seminar. Francisco Buera is senior economist at the Federal Reserve Bank of Chicago. He will present a paper entitled "The Global Diffusion of Ideas", written jointly with Ezra Oberfield.

Numerical methods for stochastic conservation laws

Friday seminar by Marcin Piwczy¨½ski from Nicolaus Copernicus University in Toru¨½, 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

H?vard 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.  

ESOP seminar. Andrea Mattozzi is Professor of Microeconomics at the European University Institute. He will present the paper "Public versus Secret Voting in Committees", written jointly with Marcos Y. Nakaguma.

The project partners came together for a workshop on Globalization, Institutions and the Welfare State at the UCL Department of Economics, London.

Jack Carlyle, ITA, Postdoc

Francesco Galuppi (UiO/Ferrara) gives the algebraic geometry seminar:

"Identifiability of polynomials and Cremona transformations."

Genetic and environmental pathways to substance use and misuse.

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.