# Wochenplan des Fachbereichs Mathematik und Informatik

|
boeckena

### Piotr Pstragowski (University of Copenhagen, Denmark): Synthetic spectra. (Oberseminar Topologie)

##### Montag, 20.01.2020 14:00 im Raum SRZ 216

To any Adams-type homology theory one can associate a notion of a synthetic spectrum, their homotopy theory is in a precise sense a deformation of the derived category of quasi-coherent sheaves on a certain algebraic stack whose generic fibre is given by the category of spectra. In this talk, I will survey some of the applications of synthetic spectra, such as the problem of algebraicity of chromatic homotopy theory, or the classification of highly-connected manifolds of Burklund-Hahn-Senger. I will also discuss some conjectures on the universal property of synthetic spectra and possible generalizations to a general homology theory.

Angelegt am Mittwoch, 02.10.2019 11:47 von boeckena
Geändert am Dienstag, 14.01.2020 07:48 von boeckena
[Edit | Vorlage]

Oberseminare und sonstige Vorträge
|
elke

### Philip Dowerk (Dresden): Analogies between finite- and infinite-dimensional unitary groups. Oberseminar C*-Algebren.

##### Montag, 20.01.2020 15:15

Angelegt am Freitag, 18.10.2019 09:26 von elke
Geändert am Donnerstag, 16.01.2020 08:59 von elke
[Edit | Vorlage]

Oberseminare und sonstige Vorträge
|
shupp_01

### Oberseminar Differentialgeometrie: Fabian Lehmann (London): Cohomogeneity one families in Spin(7) geometry

##### Montag, 20.01.2020 16:15 im Raum SR4

Spin(7) is one of the special holonomy groups on Berger's list which gives rise to Ricci flat metrics. The condition that the holonomy of an 8-manifold reduces to Spin(7) gives rise to a complicated system of non-liner PDEs. In the non-compact situation, symmetries can be used to reduce this complexity. As manifolds with special holonomy cannot be homogeneous, the most symmetric case are group actions with cohomogeneity one, i.e. where a generic orbit has codimension one. In this case the PDE system is reduced to an ODE system. I will give an overview of recent progress in the construction of complete cohomogeneity one Spin(7) holonomy metrics. All examples have an asymptotically locally conical (ALC) or asymptotically conical (AC) geometry at infinity.

Angelegt am Dienstag, 07.01.2020 10:13 von shupp_01
Geändert am Mittwoch, 08.01.2020 08:55 von shupp_01
[Edit | Vorlage]

Oberseminare und sonstige Vorträge
|
wernke

### Dr. Giacomo Del Nin (University of Warwick): Pattern formation in optimal planar partitions

##### Mittwoch, 15.01.2020 16:00 im Raum M5

Given a fixed open set $\Omega$ in the plane we focus on optimal partitions, that is, partitions of $\Omega$ into $N$ equal-area subsets that minimize the total perimeter. Hales proved in 1999 that the asymptotic optimal energy for large $N$ is given by the hexagonal honeycomb, and thus hexagonal patterns are expected. However, since $\Omega$ may not accomodate a perfectly hexagonal partition, a polycrystalline structure may emerge, where different zones of constant orientation ("grains") are separated by "grain boundaries", similarly to what happens with dislocations in materials. In this talk I will present some ongoing work on the mathematical description of such structures.

Angelegt am Montag, 13.01.2020 09:13 von wernke
Geändert am Montag, 13.01.2020 09:18 von wernke
[Edit | Vorlage]

Oberseminar Angewandte Mathematik
|
kollwit

### Johannes Schmidt-Hieber, Twente: Towards a statistical foundation of deep learning (Oberseminar Mathematische Stochastik)

##### Mittwoch, 22.01.2020 17:00 im Raum SRZ 117

Recently a lot of progress has been made in the theoretical understanding of deep learning. One of the very promising directions is the statistical approach, which interprets deep learning as a statistical method and builds on existing techniques in mathematical statistics to derive theoretical error bounds. The talk surveys this field and describes future challenges.

Angelegt am Donnerstag, 21.11.2019 15:27 von kollwit
Geändert am Donnerstag, 21.11.2019 15:29 von kollwit
[Edit | Vorlage]

Stochastik
Oberseminare und sonstige Vorträge
|
shupp_01

### Kolloquium Wilhelm Killing: Dr. Dawid Kielak (Bielefeld): Three-manifolds, Thurston's insights and a little algebra

##### Donnerstag, 23.01.2020 16:30 im Raum M5

I will survey the current state of our knowledge of 3-manifolds, focusing on what we have learned from Thurston, and on the relatively recent breakthroughs. I will then present a lightly more algebraic perspective on some of these.

Angelegt am Freitag, 11.10.2019 09:53 von shupp_01
Geändert am Donnerstag, 09.01.2020 09:47 von odermann
[Edit | Vorlage]

Veranstaltungen am Mathematischen Institut
Kolloquium FB10 und Sondervorträge
Kolloquium Wilhelm Killing
Konferenzen+Kolloquien
|
elke

### Ying-Fen Lin (Queen's University Belfast): Schur multipliers and positive extensions. Oberseminar C*-Algebren.

##### Dienstag, 14.01.2020 15:15 im Raum SRZ 216

I will first introduce scalar-valued and operator-valued Schur multipliers and their partially defined versions, and will provide a Grothendieck-type characterisation of operator-valued Schur multipliers. After a brief introduction to the matrix setting, I will talk about the positive extension problem of Schur multipliers and characterise its affirmative solution in terms of structures on an operator system associated with the domain of the multipliers. This talk will be based on joint papers with R. Levene and I. G. Todorov.

Angelegt am Freitag, 18.10.2019 09:24 von elke
Geändert am Mittwoch, 04.12.2019 09:15 von elke
[Edit | Vorlage]

Oberseminare und sonstige Vorträge
|
boeckena

### Rachael Boyd (MPI Bonn): Embedding spaces of Hopf links. (Oberseminar Topologie)

##### Montag, 27.01.2020 14:00 im Raum SRZ 216

We show that the connected component of the embedding space of links in R^3 containing the split union of m Hopf links and n unknots is homotopy equivalent to a parametrised 'round' subspace, extending work of Brendle Hatcher on the unknot case. We discuss potential generalisations and applications.This is joint work with Corey Bregman.

Angelegt am Mittwoch, 27.11.2019 07:54 von boeckena
Geändert am Dienstag, 14.01.2020 07:44 von boeckena
[Edit | Vorlage]

Oberseminare und sonstige Vorträge