
Smirnov on $\mathbb{F}_1$ and the RH
Wednesday, Alexander Smirnov (Steklov Institute) gave the first talk in the $\mathbb{F}_1$ world seminar. Here’s his title and abstract: Title: The 10th Discriminant and Tensor Powers of $\mathbb{Z}$ “We plan to discuss very shortly certain achievements and disappointments of the $\mathbb{F}_1$approach. In addition, we will consider a possibility to apply noncommutative tensor powers of $\mathbb{Z}$…

The $\mathbb{F}_1$ World Seminar
For some time I knew it was in the making, now they are ready to launch it: The $\mathbb{F}_1$ World Seminar, an online seminar dedicated to the “field with one element”, and its many connections to areas in mathematics such as arithmetic, geometry, representation theory and combinatorics. The organisers are Jaiung Jun, Oliver Lorscheid, Yuri…

Do we need the sphere spectrum?
Last time I mentioned the talk “From noncommutative geometry to the tropical geometry of the scaling site” by Alain Connes, culminating in the canonical isomorphism (last slide of the talk) Or rather, what is actually proved in his paper with Caterina Consani BCsystem, absolute cyclotomy and the quantized calculus (and which they conjectured previously to…

Alain Connes on his RHproject
In recent months, my primary focus was on teaching and family matters, so I make advantage of this Christmas break to catch up with some of the things I’ve missed. Peter Woit’s blog alerted me to the existence of the (virtual) Lake Comoconference, end of september: Unifying themes in Geometry. In Corona times, virtual conferences…

a monstrous unimodular lattice
An integral $n$dimensional lattice $L$ is the set of all integral linear combinations \[ L = \mathbb{Z} \lambda_1 \oplus \dots \oplus \mathbb{Z} \lambda_n \] of base vectors $\{ \lambda_1,\dots,\lambda_n \}$ of $\mathbb{R}^n$, equipped with the usual (positive definite) inner product, satisfying \[ (\lambda, \mu ) \in \mathbb{Z} \quad \text{for all $\lambda,\mu \in \mathbb{Z}$.} \] But…

Borcherds’ favourite numbers
Whenever I visit someone’s YouTube or Twitter profile page, I hope to see an interesting banner image. Here’s the one from Richard Borcherds’ YouTube Channel. Not too surprisingly for Borcherds, almost all of these numbers are related to the monster group or its moonshine. Let’s try to decode them, in no particular order. 196884 John…

Complete chaos and Belyiextenders
A Belyiextender (or dessinflateur) is a rational function $q(t) = \frac{f(t)}{g(t)} \in \mathbb{Q}(t)$ that defines a map \[ q : \mathbb{P}^1_{\mathbb{C}} \rightarrow \mathbb{P}^1_{\mathbb{C}} \] unramified outside $\{ 0,1,\infty \}$, and has the property that $q(\{ 0,1,\infty \}) \subseteq \{ 0,1,\infty \}$. An example of such a Belyiextender is the power map $q(t)=t^n$, which is totally…

214066877211724763979841536000000000000
If you Googled this number a week ago, all you’d get were links to the paper by Melanie Wood Belyiextending maps and the Galois action on dessins d’enfants. In this paper she says she can separate two dessins d’enfants (which couldn’t be separated by other Galois invariants) via the order of the monodromy group of…