# Trimester Seminar

Venue: HIM lecture hall, Poppelsdorfer Allee 45

**Organizers:** Michael Griebel, Wolfgang Hackbusch, Markus Hegland, Christoph Schwab

Contact: Christian Rieger

## Thursday, May 12

15:00 - 17:00 Wolfgang Hackbusch (MPI MIS Leipzig): Minimal subspaces for tensors

Abstract: For the numerical treatment of tensors suitable representations are essential. In particular, for optimization problems and for truncation reasons the representation format should be closed, since otherwise instabilities may arise (see the r-term format). There are several formats which are based on subspaces (subspace format = Tucker format, hierarchical format). In these cases the analysis of the "minimal subspaces" of a tensor helps to prove the desired results in almost general Banach tensor spaces (i.e., also the infinite dimensional case is covered, where usual compactness techniques do not help).

## Thursday, May 26

15:00 - 17:00 Reinhold Schneider** **(TU Berlin): Tensorization of vectors and novel tensor formats

## Thursday, July 14

15:00 - 16:00 Wolfgang Hackbusch (MPI MIS Leipzig): Sparse grids and tensor representations