SPP 2026 – Page 24 – Geometry at Infinity

Equivariant band matrices and Fourier series

Recall that in the first post of this series we claimed that there exists an infinite matrix \(T\) which is in the closure (in operator norm) of the band matrices with uniformly bounded entries, but for which we have \(\|T^{(R)}\| \to \infty\). Here \[T^{(R)}_{m,n} := \begin{cases} T_{m,n} & \text{ if } |m-n| \le R\\ 0 & … Continue reading

Two new presidents

Professor Volker Mehrmann from the TU Berlin was elected as the new president of the European Mathematical Society (EMS). His four-year term will start January 1st, 2019. More information can be found in the press release: link. Professor Daya Reddy was elected first president of the International Science Council (ISC). The ISC is newly founded … Continue reading

Stable minimal surfaces in 3-manifolds

Meeks-Pérez-Ros conjectured in their article “Stable constant mean curvature surfaces” (2008) the following: if a closed, connected Riemannian 3-manifold N does not admit any closed, embedded minimal surfaces whose two-sided covering is stable, then N is finitely covered by the 3-sphere. Recall that a surface is called minimal if it is a critical point of … Continue reading

Manfredo do Carmo 1928-2018

Manfredo do Carmo was a Brazilian mathematician working in differential geometry. 1978 he was an invited speaker at the ICM in Helsinki, and 1971-1973 he was president of the Brazilian Mathematical Society. Besides for his mathematical research he was also known for his textbooks.

Mathematik in der Blütezeit des Islam

Die Wikipedia veranstaltet jährlich einen Schreibwettbewerb (link). Es gibt jeweils einen Jurypreis und einen Publikumspreis, und dieses Jahr ging der Publikumspreis an einen mathematischen Artikel: Mathematik in der Blütezeit des Islam. Ein paar mehr Infos gibt es auch in diesem ScienceBlog: link.

Chromatic Number of the Plane is at least 5

The problem From the usual Euclidean plane we form the following graph: the points of the plane are the vertices of our graph, and two vertices are connected by an edge if they are exactly unit distance apart. The so-called Hadwiger-Nelson problem is to compute the chromatic number of this graph, i.e., the least amount … Continue reading

Norms of infinite matrices

This is the first post of a series of posts in which we will eventually venture deep into the realm of coarse geometry. But we will always be motivated by questions which are related to the one that we will discuss here. But our first steps into coarse geometry will be very gently: we will … Continue reading

John Roe 1959-2018

John Roe, the founder of coarse index theory, passed away last month after a long fight against cancer. His web page is still online ( http://sites.psu.edu/johnroe/ ) and can be visited to get a glimpse not only of his mathematical work, but also of his personal life and all the things in the world that … Continue reading