## November 2020

## December 2020

### Eindhoven SPOR Seminar

Guillem Perarnau Extremal stationary values for directed random graphs In this talk, we will discuss the minimum positive value of the stationary distribution of a random walk on a directed random graph with given (bounded) degrees. While for undirected graphs the stationary distribution is simply determined by the degrees, the graph geometry plays a major role in the directed case. Understanding typical stationary values is key to determining the mixing time of the walk, as shown by Bordenave, Caputo, and…

Find out more »## January 2021

### Eindhoven SPOR Seminar

Piotr Zwiernik Modelling with positive dependence: graphical models, and convex optimization Probability distributions that are multivariate totally positive of order 2 (MTP2) appeared in the theory of positive dependence and in statistical physics through the celebrated FKG inequality. The MTP2 property is stable under marginalization, conditioning and it appears naturally in various probabilistic graphical models with hidden variables. Models of exponential families with the MTP2 property admit a unique maximum likelihood estimator. In the Gaussian case, the MLE exists also…

Find out more »## February 2021

### Eindhoven SPOR Seminar

Christian Hirsch (RUG) Modeling synaptic plasticity through dynamically reinforced random networks Graph-based Pólya urns are a promising approach to model random processes on networks that exhibit self-reinforcing phenomena such as the ones inspired by synaptic plasticity in neuroscience. As in classic Pólya urns, the network-based analogues behave very differently in regimes of weak and strong reinforcement. At weak reinforcement, the effect of reinforcement disappears in the long-term limit. At strong reinforcement, we observe clear localization phenomena. Moreover, we present a…

Find out more »### Workshop “Data-driven solutions for containing the spreading of COVID-19”

Summary The aim of this workshop is to bring together researchers and companies in the Netherlands interested in or already working on data-driven solutions for reducing the spread of COVID-19. Format Online Organizers We are a consortium of four universities (TU Eindhoven, UMC Leiden, University of Utrecht, University of Twente) and two data science companies (Mezuro, Ilionx) that aims to develop a predictive dashboard for local corona outbreaks, funded by ZonMw grant 10430 03291 001 `Mobility and behavior-based early-warning system…

Find out more »### Eindhoven SPOR Seminar

Mikloz Racz (Princeton) An Adversarial Perspective on Network Disruption I will discuss a simple new model of network disruption, where an adversary can take over a limited number of user profiles in a social network with the aim of maximizing disagreement and/or polarization in the network. I will present both theoretical and empirical results. Theoretically, we characterize aspects of the adversary’s optimal decisions and prove bounds on their disruptive power. Furthermore, we present a detailed empirical study of several natural…

Find out more »## March 2021

### Eindhoven SPOR Seminar

Tim Oosterwijk (UM) The secretary problem with independent sampling Sequential decision making under uncertainty is a basic problem that bridges several areas. Examples include online algorithms in computer science, and optimal stopping problems with stochastic input in the field of operations research and applied probability. In this talk, I will discuss the secretary problem, where we are faced with an online sequence of elements with values. Upon seeing an element we have to make an irrevocable take-it-or-leave-it decision. The goal…

Find out more »### Eindhoven SPOR Seminar

Christian Brownlees (UPF) Community Detection in Partial Correlation Network Models We introduce a class of partial correlation network models with a community structure for large panels of time series. In the model, the series are partitioned into latent groups such that correlation is higher within groups than between them. We then propose an algorithm that allows one to detect the communities using the eigenvectors of the sample covariance matrix. We study the properties of the procedure and establish its consistency.…

Find out more »## April 2021

### Eindhoven SPOR Seminar

Christopher Hojny (TU/e) Possibilities and Limitations of Symmetry Handling Cutting Planes Branch-and-bound is a well-established tool for solving combinatorial optimization problems. If the combinatorial problem contains symmetric structures (such as symmetric graphs or identical objects), however, branch-and-bound will also explore many symmetric, and thus unnecessary, subproblems during the solving process. To accelerate the solution procedure, a standard technique is to detect symmetries of the problem and to add inequalities (cutting planes) to the problem formulation that prevent the solver from…

Find out more »## May 2021

### Eindhoven SPOR Seminar

Matthieu Jonckheere (UBA) Distance learning using Euclidean percolation: Following Fermat's principle In unsupervised statistical learning tasks such as clustering, recommendation, or dimension reduction, a notion of distance or similarity between points is crucial but usually not directly available as an input. We proposed a new density-based estimator for weighted geodesic distances that takes into account the underlying density of the data, and that is suitable for nonuniform data lying on a manifold of lower dimension than the ambient space. The…

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