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Thursday, 21.09.2017, 14.00 Uhr (WIAS-ESH)
Seminar Numerische Mathematik
Dr. Ch. Freysoldt, Max-Planck-Institut für Eisenforschung, Düsseldorf:
Vortrag entfällt / Lecture not applicable
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin
Tuesday, 26.09.2017, 13.30 Uhr (WIAS-ESH)
Seminar Numerische Mathematik
Y. Ren, Dalian University of Technology, China:
On tetrahedralisations containing knotted and linked line segments
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
This talk considers a set of twisted line segments in 3d such that they form a knot (a closed curve) or a link of two closed curves. Such line segments appear on the boundary of a family of 3d indecomposable polyhedra (like the Schönhardt polyhedron) whose interior cannot be tetrahedralised without additional vertices added. On the other hand, a 3d (non-convex) polyhedron whose boundary contains such line segments may still be decomposable as long as the twist is not too large. It is therefore interesting to consider the question: when there exists a tetrahedralisation contains a given set of knotted or linked line segments?
In this talk, we studied a simplified question with the assumption that all vertices of the line segments are in convex position. It is straightforward to show that no tetrahedralisation of 6 vertices (the three-line-segments case) can contain a trefoil knot. When the number of twisted line segments is larger than 3, it is necessary to create new interior edges to form a tetrahedralisation. We provided a detailed analysis for the case of a set of 4 twisted line segments. We show that the addition of a pair of new interior edges decomposes the original knot (or link) into two links (or knots) with less crossing numbers. This leads to a crucial condition on the orientation of pairs of new interior edges which determines whether this set is decomposable or not. We then prove a new theorem about the decomposability for a set of n (n ≥ 3) twisted line segments. This theorem implies that the family of polyhedra generalised from the Schönhardt polyhedron by Rambau are all indecomposable.

Host
WIAS Berlin
October 4 – 6, 2017 (WIAS-ESH)
Workshop/Konferenz: Homogenization Theory and Applications
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin
SFB 1114: Scaling Cascades in Complex Systems
SFB 910 ``Control of self-organizing nonlinear systems: Theoretical methods and concepts of application''
October 11 – 14, 2017 (WIAS-ESH)
Workshop/Konferenz: SPP 1962 Autumn School 2017 ``Nonsmooth Structures in Mathematical Models''
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
There will be an autumn school on "Nonsmooth Structures in Mathematical Models" at the Weierstrass Institute in Berlin as part of the DFG SPP 1962. We will have three lecturer courses: 'Splitting algorithms in nonsmooth convex and nonconvex optimization' by Prof. Dr. Bot, 'Systems with rate independence: models, sensitivity, optimization' by Prof. Dr. Brokate, 'Problems with equilibrium constraints: Theory and numerics' by Prof. Dr. Outrata. More details of the program can be found at http://www.wias-berlin.de/workshops/sppsummerschool2017/program.jsp. The autumn school will start at 4pm on the 11th October and end around 12:30pm on the 14th October. This school is primarily intended for the doctoral and postdoctoral students. Interested parties may apply to register; the number of available places is limited so registration is mandatory for all and the deadline for registration is 30th August. There is no registration fee, however travel costs will not be paid. For full details and registration, please see http://www.wias-berlin.de/workshops/sppsummerschool2017/index.jsp.

Host
WIAS Berlin
DFG Schwerpunktprogramm 1962
Monday, 16.10.2017, 14.00 Uhr (WIAS-ESH)
INSTITUTSKOLLOQUIUM
Dr. S. Amiranashvili, WIAS:
Negative frequency radiation in optical fibers
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin