Stefan Horst Sommer

Primary fields of research

My research focus is on modeling and statisttics of non-linear data with application to shape spaces, functional data analysis, and image registration. This includes foundational and algorithmic aspects of statistics on manifold valued data, and computational modeling and statistical analysis of deformations occuring in computational anatomy.

Selected papers:

• A Geometric Framework for Stochastic Shape Analysis / Alexis Arnaudon, Darryl D. Holm, and Stefan Sommer, accepted for Foundations of Computational Mathematics, 2018, https://arxiv.org/abs/1703.09971.
• Modelling Anisotropic Covariance using Stochastic Development and Sub-Riemannian Frame Bundle Geometry .  Accepted for publication in Journal of Geometric Mechanics, 2016.
• Higher-order Spatial Accuracy in Diffeomorphic Image Registration / Henry O. Jacobs and Stefan Sommer. Journal of Geometry, Imaging and Computing, 2015.In: Geometry, Imaging and Computing, Vol. 1, No. 4, 2014, p. 447-484.
• Anisotropic Distributions on Manifolds: Template Estimation and Most Probable Paths / Stefan Sommer.
  Information Processing in Medical Imaging (IPMI) 2015
• A nonlinear mixed-effects model for simultaneous smoothing and registration of functional data. / Rakêt, Lars Lau; Sommer, Stefan Horst; Markussen, Bo.In: Pattern Recognition Letters, Vol. 38, 2014, p. 1-7.
• Higher-order momentum distributions and locally affine LDDMM registration. / Sommer, Stefan Horst; Nielsen, Mads; Darkner, Sune; Pennec, Xavier.In: S I A M Journal on Imaging Sciences, Vol. 6, No. 1, 2013, p. 341-367.
• Sparse multi-scale diffeomorphic registration : The Kernel Bundle Framework. / Sommer, Stefan Horst; Lauze, Francois Bernard; Nielsen, Mads; Pennec, Xavier.In: Journal of Mathematical Imaging and Vision, Vol. 46, No. 3, 2013, p. 292-308.

Video recordings of talks:

• Evolution Equations with Anisotropic Distributions and Diffusion PCA, Geometric Science of Information, 2015

Current research

Current projects:

• Center for Stochastic Geometry and Advanced Bioimaging
• Security Assessment of Renewable Power Systems (SARP)

Short presentation

For full-text papers, please see my profile at ResearchGate https://www.researchgate.net/profile/Stefan_Sommer

News:

• April 2019: The faculty of Science, University of Copenhagen has appoined me head of studies for the new BSc education in Machine learning and data science at the Department of Computer Science (DIKU).
• November 2018: I am looking for a postdoc with a solid mathematical background for a position in reinforcement learning link. The challenge is to make algorithms daydream.
• April 2018: Our (Alexis Arnaudon, Darryl Holm) paper A Geometric Framework for Stochastic Shape Analysis is accepted for Foundations of Computational Mathematics.
• September 2017: Computations in computational anatomy and, in more generality, differential geometry can be both easily and efficiently expressed with symbolic computations using e.g. the Theano framework. Line Kuhnel presented our paper Computational Anatomy in Theano at the MFCA workshop at MICCAI '17. We are currently extending the methods to a.o. Lie groups, see the code in the repository https://bitbucket.org/stefansommer/theanogeometry/
• Two papers (IPMI'17 and preprint) on stochastic shape analysis: arXiv:1612.05323 and arxiv:1703.09971.
• I was appointed Associate Professor by the Faculty of Science, University of Copenhagen by April 1st, 2017.
• Interested in statistics of nonlinear data? Please see this phd course that Aasa Feragen and I organize in June 2017 in Copenhagen. Update (2/5 '17): Tentative program is now online.
• November 2016: My paper Anisotropically Weighted and Nonholonomically Constrained Evolutions on Manifolds was accepted for publication in Entropy.
• August 2016: Our paper Modelling Anisotropic Covariance using Stochastic Development and Sub-Riemannian Frame Bundle Geometry was accepted for publication in Journal of Geometric Mechanics.
• August 2016: The Workshop on Geometry and Stochastics of Nonlinear, Functional and Graph Data is running on Bornholm gathering world class researchers in non-linear statistics, functional data analysis, and random topology and graphs. The workshop that is organized by Eva Vedel Jensen, Aasa Feragen and Stefan Sommer is part of the activities of the CSGB centre supported by the Villum foundation. See also
  http://csgb.dk/activities/2016/geometry/
  http://www.dr.dk/radio/ondemand/p4bornholm/regionale-nyheder-2016-08-15-12-30-4#!/
  http://diku.dk/nyheder/2016/tvaerfaglighed-forskerkanoner-bornholm
• July, 2016: I presented joint work with Alexis Arnaudon and Darryl Holm, Imperial College London, on stochastics on large deformations, estimation and Brownian bridge simulation at IMS, National University of Singapore, see http://www2.ims.nus.edu.sg/Programs/016shape/wk.php .
• Jan. 2016: ForskEL has funded the project Security Assessment of Renewable Power Systems (13,5 mill.) The project will be lead by Hjörtur Jóhannsson, DTU. Stefan Sommer will serve as leader of WP4, scientific coordinator, and member of the project management team.
• Dec. 2015: I have joined the editorial board of the Journal of Mathematical Imaging and Vision (JMIV) as associate editor.
• Nov. 2015: The Proceedings of Math on the Rocks shape analysis workshop in Grundsund, 2015 (co-edited with Klas Modin) are now online.
• July 2015: Stefan Sommer was awarded an Honourable Mention at the Information Processing in Medical Imaging (IPMI) 2015 conference for his paper Anisotropic Distributions on Manifolds: Template Estimation and Most Probable Paths and corresponding talk. See also DIKU news.

See also:

• Twitter: @sommercsmath
• Google Scholar: http://scholar.google.com/citations?user=GGh0haAAAAA
• Github: http://github.com/stefansommer/ / http://github.com/nefan/