Ett informationsblad från matematiska institutionen vid Linköpings universitet. Material till Lite Mat lämnas till Maud Lindström litemat@mai.liu.se senast torsdagar kl 12.00.

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***LITE MAT***

Ett informationsblad från matematiska institutionen vid Linköpings universitet

v4 2001

Matematiska kollokviet

Fredagen den 26 januari kl. 13.15 - 14.15 talar Stefan Rauch-Wojciechowski,

Three theorems on integrable Newton equations

Sammanfattning: The Newton equation which says that the acceleration is equal to an external force is fundamental for the whole analytical mechanics. The standard theory studies extensively the case when the force is generated by the potential V(q). The Kepler problem of motion of Earth around Sun: V(q)= k/|q| is a pivotal example in this theory. A new theory of Newton equation with quasipotential forces , developed by us, gives new light on many results of integrable dynamics and leads to new, interesting mathematics. I shall present three important theorems within this theory: on an effective criterion of separability for potential forces, on triangular systems of Newton equations and on ``cofactor pair´´ systems of Newton equation.

Fredagen den 2 februari kl. 13.15 - 14.15 talar Professor Alexander P. Veselov, Loughborough University,

The Hadamard problem and generalised quantum Calogero-Moser systems

Sammanfattning: The Hadamard problem of description of all second order hyperbolic equations satisfying Huygens' principle (in the narrow Hadamard sense) is one of the classical open problems which still remains open. Over the last decade a substantial progress in this direction has been made as a result of the discovered relations between this problem and the problem of classification of all integrable generalisations of the quantum Calogero-Moser system. In the talk these relations due to Yu. Berest, O. Chalykh, M. Feigin and the speaker will be discussed.

Lokal: MAI:s seminarierum Beurling

Välkomna!

Lars-Erik Andersson, Anders Björn, Svante Linusson och Stefan Rauch

NSC Seminar on High Performance Computing:

Mechanics of the Heart

Prof. Matts Karlsson, Dept. of Biomechanical Engineering (IMT), Linköping University

Time: Tuesday January 23, 2001 at 16.15-17.00

Place: Room Schrödinger (E324),
F-building (Fysikhuset), Campus Valla, Linköping University

Abstract:

Non-invasive imaging is the clinical tool of the future for diagnosis of heart diseases. A unique velocity measurement technique enables us to measure 4D (3D+time) velocity fields. By applying newly developed methods in engineering mechanics and image processing we have pioneered the work on visualisation and taken the newly developed methods into clinical practice. The trend for the next generation in diagnostic tools will be to go from qualitative to quantitative.

Thus, the work includes the possibility to extract established parameters, such as pressure differences, completely non-invasively (without inserting a pressure catheter) from the velocity data. Using a similar data acquisition technique for the velocities of the heart muscle, a 4D (3D+time) mapping of the strain and even stress can be used to describe the mechanical properties of the heart muscle.

The data sets acquired are large (>512 MB for one heart beat). Gradient estimation and computation of important parameters are difficult both due to the size of the data sets but also due to the available time - if these methods are to be used clinically, computational time is very important. Therefore, both increased computer power and faster algorithms are important for the future. In this presentation I will present the work in the group and show some examples of the current research as well as point out a few new directions for the future.

Aim:

This seminar is part of a series arranged by the National Supercomputer Centre (NSC) at Linköping University. Seminars presented in the series focus on various aspects of high performance computing in scientific and technological research, such as results from actual computations, numerical algorithms, as well as hardware and software solutions in high performance computer systems. The seminars are intended for a scientific cross-disciplinary audience, i. e., scientists, engineers and students with an interest in computational modelling as a research tool.

Welcome!

Jan Fagerström
National Supercomputer Centre (NSC)
URL: www.nsc.liu.se

Seminarium i optimeringslära

Onsdag den 24 januari kl 13.15 talar Sven Erlander om

Welfare, Freedom of Choice and Composite Utility in the Logit Model

Abstract:

Discrete choice models characterize the alternatives in the choice set by utilities/attributes. The decision making is described by a probability distribution over the choice set. The probability distribution represents utility maximizing behavior. In this seminar I introduce a welfare measure based on expected observed utility and expected freedom of choice for the simple one parameter logit model. In this case the welfare measure turns out to be the so called composite utility. This means that the composite utility can be intrepreted as the combined benefit of expected observable utility and expected freedom of choice. The proposed welfare measure can be extended to the linear-in-parameters logit model and nested logit models and others. The proposed welfare measure is formulated in terms of the choice probability distribution. It depends on the form of the probabilities, but not on any particular derivation of the distribution.

Lokal: Kompakta rummet

Välkomna!

Seminarium i matematisk statistik

Onsdag den 24 januari, kl. 13.15 - 15.00 håller Prof. Lars Holst, Inst.för matematik, KTH, ett seminarium med titeln

Stein-Chens metod för Poissonapproximation

Sammanfattning: När är en summa av indikatorvariabler med "god approximation" Poissonfördelad? För att belysa detta genomgås Stein-Chens metod och koppling. Tekniken tillämpas på några exempel. Inga omfattande förkunskaper i sannolikhetsteori förutsätts.

Lokal: Seminarierum Beurling

Information: Timo Koski, ank. 1454,
tikos@mai.liu.se

Mer information om MAI finns på under MAIs hemsida
Material till Lite Mat lämnas till Maud Lindström senast torsdagar kl 12.00.
Tel 013-281405, Fax 013-100746, Email: litemat@mai.liu.se

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