Welcome to the webpage of our seminar. Your organizers are Carlos Amendola, Eliana Duarte and Thomas Kahle.

Here’s our line-up:

Next: March 13, 2023

• Location: MPI-MiS Leipzig
• Time: 10:00 am
• Speaker: Jane Coons (U Oxford)
• Title: Rational partition models under iterative proportional scaling
• Abstract: The classical iterative proportional scaling algorithm, or IPS, numerically computes the maximum likelihood estimate of a given vector of counts for a log-linear partition model. We investigate the conditions under which IPS produces the exact maximum likelihood estimate, or MLE, in finitely many steps. Since IPS produces a rational function at each step, a necessary condition is that the model must have rational maximum likelihood estimator. However, the convergence is highly parametrization-dependent; indeed, one parametrization of a model may exhibit exact convergence in finitely many steps while another does not. We introduce the generalized running intersection property, which guarantees exact convergence of IPS. As the name suggests, this strictly generalizes the well-known running intersection property for hierarchical models. This generalized running intersection property can be understood in terms of the toric geometry of the log-linear model, and models that satisfy this property can be obtained by performing repeated toric fiber products of linear ideals. We also draw connections between models that satisfy the generalized running intersection property and balanced, stratified staged trees.

Outlook

• April 24, 2023
  • Location: MPI-MiS Leipzig
  • Speaker Lior Pachter (CalTech)
• May 25, 2023
  • Location: OvGU Magdeburg
  • Speakers: Anja Janßen and Felix Reinbott.

Past events

• February 20, 2023 at TU Berlin
  • Location: TU Berlin, Math Building, MA 608
  • Time: 14:00 - 15:00
  • Speaker: Paul Breiding (U Osnabrück)
  • Title: Algebraic Compressed Sensing
  • Abstract: We introduce the broad subclass of algebraic compressed sensing problems, where structured signals are modeled either explicitly or implicitly via polynomials. This includes, for instance, low-rank matrix and tensor recovery. We employ powerful techniques from algebraic geometry to study well-posedness of sufficiently general compressed sensing problems, including existence, local recoverability, global uniqueness, and local smoothness.
  • Notes: There will be a pretalk aimed at students taking place at 11:30-12:00 in MA 608, this will be followed by lunch 12:15-13:45. At 17:30 we will walk to have dinner nearby. You are welcome to join!
• January 16, 2023, MPI-MiS Leipzig
  • Speaker: Peter Stadler (U Leipzig)
  • Title: Relational Data in Phylogentics
  • Abstract: In the course of investigation evolutionary relationships found in the genomes a set of species, several binary relations appear. For example “best matches” refer pairs of genes x and y so that y is one of the closest relatives of x in the species that harbors y. Orthology designates pairs of genes whose last common ancestor is a speciation event. Horizontal gene transfer is related to the lower diverence time relation, satisfied by a pair of genes that is younger than the divergence of the species in which they reside. I will sketch the connections between the relations and the the information that they convey about the gene trees, the phylogeny of the underlying species, and the reconciliation of gene and species trees.