Alexander Engel – Page 2

Operators of finite propagation

In the starting post of this series we considered infinite band matrices (with uniformly bounded entries) acting on infinite vectors and asked at the end the question how to determine whether a given matrix, which is not a band matrix, can be approximated by such. Today we provide the setup in order to answer this question properly in … Continue reading

Strong cosmic censorship conjecture

The cosmic censorship conjectures concern the singularities arising in general relativity. In May the QuantaMagazine published an article (link) about a potential disproof of a strong version of the cosmic censorship conjecture. This article is nicely written and I recommend everybody interested in general relativity reading it. The preprint the QuantaMagazine refers to is arXiv:1710.01722 … Continue reading

News around the ICM 2018

The ICM 2018 is currently taking place in Rio de Janeiro. Here are the prize winners of the IMU prizes and of the K-theory foundation, and the new IMU Executive Committee. The Fields medallists 2018 are Caucher Birkar, Alessio Figalli, Peter Scholze, and Akshay Venkatesh. There are also many more prizes and medals that are … Continue reading

Contractible 3-manifolds and positive scalar curvature

It is known that \(\mathbb{R}^3\) admits a complete metric of uniformly positive scalar curvature. In fact, for any closed manifold \(X\) and any \(k \ge 3\) the manifold \(X \times \mathbb{R}^k\) admits a complete metric of uniformly positive scalar curvature by a result of Rosenberg and Stolz (link). Now there exist contractible, open 3-manifolds which are not … Continue reading

Prizes, prizes, prizes

Several prizes have been awarded in the past few weeks to mathematicians. Kyoto Prize The Kyoto Prize 2018 in the category Basic Sciences was awarded to Masaki Kashiwara from the RIMS at Kyoto University. (announcement) The Kyoto Prize is awarded annually to “those who have contributed significantly to the scientific, cultural, and spiritual betterment of mankind” … Continue reading

Peter Scholze a new director at MPI Bonn

Peter Scholze is a new director at the Max Planck Institute for Mathematics in Bonn. You can read a bit more about this news here: link.

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.