## November – Dezember 2017

Nov
28
Di
Paul Breiding, (MPI MIS, Leipzig): Random Spectrahedra
Nov 28 @ 10:00 – 11:00
Nov
29
Mi
Workshop: Berlin-Leipzig workshop in analysis and stochastics (day 1)
Nov 29 @ 13:30 – 18:00

https://www.mis.mpg.de/calendar/conferences/2017/Berlin-LE-WS/index.html

Felix-Klein Colloquium: Günter M. Ziegler (Berlin)
Nov 29 @ 16:30 – 17:30

Semi-algebraic sets of integer points.

We look at sets of integer points in the plane,
and discuss possible definitions of when such a set
is “complicated” — this might be the case if it
is not the set of integer solutions
to some system of polynomial equations and inequalities.
Let’s together work out lots of examples,
and on the way let’s try to develop criteria
and proof techniques …

The examples that motivated our study come
from polytope theory: Many question of the type
“What is the possible pairs of
(number of vertices, number of edges)
for 5-dimensional polytopes?”
have been asked, many of them with simple and complete
Our main result says: In some cases it IS complicated!
(Joint work with Hannah Sjöberg.)

Nov
30
Do
Workshop: Berlin-Leipzig workshop in analysis and stochastics (day 2)
Nov 30 @ 09:00 – 18:00

https://www.mis.mpg.de/calendar/conferences/2017/Berlin-LE-WS/index.html

Marius Yamakou, (MPI MIS, Leipzig): to be announced
Nov 30 @ 15:00 – 16:30
Nov 30 @ 15:15 – 16:45
Dez
1
Fr
Workshop: Berlin-Leipzig workshop in analysis and stochastics (day 3)
Dez 1 @ 09:00 – 12:30

https://www.mis.mpg.de/calendar/conferences/2017/Berlin-LE-WS/index.html

Dez
4
Mo
Wolfgang Löhr, (TU Chemnitz): Continuum limits of tree-valued Markov chains and algebraic measure trees
Dez 4 @ 11:00 – 12:30

In some approaches to the reconstruction of phylogenetic trees, Markov chain Monte Carlo methods are used. These in turn use simple base-chains on the set of (binary) trees of a given size $N$. It is at least of mathematical interest (but might also help to understand properties of such Markov chains when the trees are large) to consider limit processes as $N$ tends to infinity and the time is suitably sped up. Here, we have to decide in which state space we are working, i.e., what kind of objects we want to consider as “continuum trees” in the limit, and what we mean by “limit”.
One by now almost-classical approach is to work in a space of metric measure spaces, but while it has proven successful in some situations, it seems difficult to prove convergence in others. Motivated by a particular Markov chain, the Aldous chain on cladograms, where existence of a limit process has been conjectured almost two decades ago, we introduce an alternative state space. We define the objects by a “tree structure” (formalized by a branch-point map) instead of a metric structure and call them algebraic measure trees. In this new state space, we are able to
prove convergence of the Aldous chain to a limit process with continuous paths.
(joint work with Anita Winter and Leonid Mytnik)

New Faces of the MPI present their research interests
Dez 4 @ 14:00 – 16:00

Faces of the December:
Ulrich Menne
Max Pfeffer
Andre Uschmajew

Dez
5
Di
Ibrahim Nonkane, (Université Ouaga II): Discriminants of complete intersection space curves
Dez 5 @ 10:00 – 11:00

In this talk, a new approach to the theory of discriminants for complete intersection curves in the 3-dimensional projective space will be discussed.

Jeff Sommars: Algorithms and Software for Computing Tropical Prevarieties
Dez 5 @ 11:00 – 12:00
Letzte Änderung: 15. Mai 2013