I learnt the following from my son Léo: the teacher asks to compute ; that’s easy But no! The actual question is to compute times ! We must correct this! But it’s just as easy without starting from scratch: we turn the “plus” cross a quarter turn on the left-hand side: and then switch the […]

Just after the end of the semester last week, I went to a short meeting organized by J. Keating, Z. Rudnick and T. Wooley, in the stately English house of Chicheley Hall, where the Royal Society has a conference center. This was quite a fun occasion, and not only because the curtains had one the […]

In February, I was invited to give talks in Bristol and Oxford, and I spent the night after the second talk in a guest room of Worcester College. While looking at the brochure explaining the history of this college, I noticed that a previous guest had left a cryptic inscription, which I took a photograph […]

No, this post is not an exercise in tautological reasoning: the point is that the word “discrete” is relatively overloaded. In the theory of automorphic forms, “discrete spectrum” (or “spectre discret”) is the same as “cuspidal spectrum”, and refers to those automorphic representations (of a given group over a given global field ) which are […]

After I wrote my last post on the condition in a group, I had a sudden doubt concerning the case in which this arose: there we assume that we have a coset such that for all . I claimed that this implies , but really the argument I wrote just means that : for all […]