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Seminario: “Trust your data or not - Standard remains Standard (QP); implications for robust clustering in social networks”

Venerdì 6 Aprile 2018, ore 14:30 - Aula 1BC45 - Immanuel Bomze

ARGOMENTI: Seminari

Venerdì 6 Aprile 2018 alle ore 14:30 in Aula 1BC45, Immanuel Bomze (VCOR/ISOR and DataScience@UniWien) terrà un seminario dal titolo: “Trust your data or not - Standard remains Standard (QP); implications for robust clustering in social networks”.

Abstract
In a Standard Quadratic Optimization Problem (StQP), a possibly indefinite quadratic form (the simplest nonlinear function) is extremized over the standard simplex, the simplest polytope. Despite of its simplicity, this nonconvex continuous optimization model is quite versatile and can even serve to solve discrete problems like the Maximum-Clique-Problem. Here we will focus on Clustering in Social Networks applications in a Machine Learning context.
A fundamental problem arising in social network analysis regards the identification of communities (e.g., work groups, interest groups), which can be modeled naturally with the framework of StQP.
However the problem data are uncertain as the strength of social ties can only be roughly estimated based on observations. Therefore the robust counterpart for these problems refers to uncertainty only in the objective, not in the constraints. It turns out that for the StQP, most of the usual uncertainty sets do not add complexity to the robust counterpart.
On the other hand, it is well known that most probably within this problem class, a generic StQP instance is not too hard to solve as the worst cases are hidden in relatively thin manifolds of the class. These hard instances allow for remarkably rich patterns of coexisting local solutions, which are closely related to practical difficulties in solving StQPs globally.
Based upon joint work with Michael Kahr, Markus Leitner, Werner Schachinger and Reinhard Ullrich (all Univ.Wien).

Short bio
Immanuel M. Bomze was born in Vienna, Austria, in 1958. He received the degree Magister rerum naturalium in Mathematics at the University of Vienna in 1981. After a postgraduate scholarship at the Institute for Advanced Studies, Vienna from 1981 to 1982, he received the degree Doctor rerum naturalium (Ph.D.) in Mathematics at the University of Vienna.
After his Habilitation in 1987, he held several visiting research positions at various research institutions across Europe, the Americas, Asia and Australia. He also gained some practical Operations Research experience during his work as a research mathematician in the Business & Marketing Research/Operations Research group of the national incumbent telecommunication operator Telekom Austria 2002-2004. Since 2004, he holds a chair (full professor) of Applied Mathematics and Statistics at the University of Vienna and since 2009, Bomze serves as the Study Director of the Abraham-Wald-PhD program in Statistics and Operations Research, located at the Faculty of Business, Economics, and Statistics at this university.
Bomze’s research interests are in the areas of nonlinear optimization, qualitative theory of dynamical systems, game theory, mathematical modelling and statistics, where he has edited one and published four books, as well as over 100 peer-reviewed articles in scientific journals and monographs. The list of his co-authors comprises over seventy scientists from
more than a dozen countries in four continents. In 2014 he was elected Fellow of EurOpt, the Continuous Optimization Working Group of EURO, the Association of European Operational Research Societies http://europt.iam.metu.edu.tr.
As a member of program and/or organizing committees, he co-organized various scientific events and he is an Associate Editor for five international journals. For several science foundations and councils (based in Canada, the Czech Republic, Germany, Great Britain, Hong Kong, Israel, Italy, the Netherlands, Norway, Portugal, Singapore, Spain, USA), and
for almost 50 scientific journals he acted as a reporting referee. 2011–2017 he served as an Editor (Co-EiC) of the European Journal of Operational Research, one of the worldwide leading journals in the field. Moreover, he serves as the Austrian Representative in the Management Committee of the European COST Action CA16228 European Network for Game Theory. Bomze co-founded the Vienna Center of Operations Research (VCOR) and serves as its co-director. Recently he was elected president of EURO, commencing office (as the president-elect) in 2018.