# E. Kowalski's blog

Comments on mathematics, mostly.

## Sharks and Snakes

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The Swiss stereotypes do not usually suggest a great sense of humor. But since I’ve been in Zürich, I’ve noticed a certain style of quiet understated humor, in particular in advertising.

Here’s one ad for the most famous vegetarian restaurant in Zürich (probably the best in the world):

Snakes

Here’s an ad for the Zürich public transportation system; the left-hand man is a right-wing politician, and the right-hand one a socialist (I had to look this up; I’m not really up to date on local politics), and the ad says that fortunately there is a tram stop on average every 300 meters…

Politicians

Here’s a recent ad to warn against swimming in the wrong places in the river, despite the absence of sharks (Hai means shark in German):

Sharks

September 4th, 2014 at 6:53 pm

Posted in Arts,Switzerland

## My office in 1870

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The historical “main” building of ETH was finished 150 years ago, in 1864. Or rather, the first version was finished, since it was altered and extended quite a bit since then (as did the surroundings!). In a recent NZZ article, I saw this picture

ETH in 1870

of the building as it looked in 1870. The red square indicates where my office is located…

August 23rd, 2014 at 8:23 pm

## The Spring menagerie

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I think readers can legitimately complain that not only have I not added a new post for a long time, but more schockingly, my last animal-related one goes back more than one year. So, to celebrate the recent belated aperçus of spring in Zürich and around, here are some pictures:

The first two are cheating, since they come from the Masoala Hall — but the first one illustrates the beautiful views from the very new canopy walk:

while the second is a rarely-seen lizard

Next comes a well-camouflaged bird, this one from a park in Graz

and another one from the aforementioned canopy

after which come a frog,

a snail,

and more frogs:

Hopefully more animal pictures will come before a year passes!

May 6th, 2013 at 9:24 pm

## Stickelberger’s copy of Jacobi’s “Canon arithmeticus”

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I am currently the head of the Mathematics Library at ETH (which is separate from the main library). A few days ago, I surveyed some of the (relatively) old books in our collection with one of the librarians, just to see if some of these should be handled in a special way. We didn’t find anything really out of the ordinary (no copy of Poincaré’s works heavily annotated by H. Weyl, I’m afraid), but one book has some historical interest: it is (or seems to be) Stickelberger’s copy of Jacobi’s “Canon arithmeticus”

a table of primitive roots and discrete logarithms for primes up to 1000.

Stickelberger’s signature is found on one of the first pages

The table itself, as it took me a few minutes to understand (my Latin being non-existent), lists for each prime $p\leq 1000$ the “Numeri” $1\leq N\leq p-1$ and the “Index” $1\leq I\leq p-1$, which are defined by the relation
$N=\rho^I,$
for some primitive root $\rho$ modulo $p$, which can be identified easily by looking for the number for which $I$ is equal to $1$:
$\rho=\rho^1.$

So above we see that Jacobi selected $2$ as primitive root modulo $5$ and $11$, and $3$ as primitive root modulo $7$, or $6$ as primitive root modulo $13$. Obligingly, he also indicates the factorization of $p-1$ (so that all primitive roots can be easily found by checking whether the corresponding index is coprime with $p-1$).

Like the copy which was digitized by Google, Stickelberger’s has a list of corrections at the end, and most (if not all: I didn’t check…) of these are incorporated in pencil in the main text, as here with $p=71$:

However, Stickelberger (if it was him) also had another list of corrections, written down on a separate loose sheet of paper inserted at the end of the book.

These corrections are reproduced from the paper On quasi-mersennian numbers by Lieutenant Colonel Allan Cunningham in Vol. 41 of the Messenger of Mathematics (a volume which seems famous in statistical circles because it contains, ten pages later, an important paper of R.A. Fisher on maximum likelihood…) But even Cunningham’s corrections contain a few mistakes, which Stickelberger reports (though with question marks):

Indeed, for $p=757$, the primitive root chosen by Jacobi is $\rho=2$ and we have
$2^{468}=565\bmod{757},$
instead of $568$ reported by Cunningham (and $168$ in the Canon).

As far as I could see during my quick inspection, there are no further annotations or comments by Stickelberger, nor any date indicating when he acquired this book. The publication date is 1839, and the only other indication is that the volume of the Messenger of Mathematics with Cunningham’s paper appeared in 1912. I also do not known when and how the book entered the collection of ETH.

February 3rd, 2013 at 5:45 pm

## Upcoming events!

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There will be quite a few number-theoretic activities that I will be involved-in this year. In chronological order:

(1) In March, on Friday the 15th and Saturday the 16th, there will first be the 10th edition of the ETH-EPFL Number Theory Days, this time in Lausanne. The web page is currently not very informative (except for links to the previous editions…), but the speakers this year will be L. Berger (ENS Lyon), E. Lindenstrauss (Hebrew University), H. Oh (Brown University), N. Templier (Princeton University) and J. Wolf (École Polytechnique). This is organized by Ph. Michel and myself.

(2) Immediately following, there will be a conference on “Equidistribution in number theory and dynamics” at the Forschungsinstitut für Mathematik of ETH, organized jointly by M. Einsiedler, E. Lindenstrauss, Ph. Michel and myself, from March 18 to 22. There is a web page with the current list of speakers. We would especially like to invite young mathematicians to apply here for financial support if they wish to attend this conference (the deadline indicated is January 15th, but a few more days should not hurt).

(3) During the first week of June, again at FIM, G. Wustholz and myself are organizing a conference to celebrate the 25th anniversary of the Number Theory Seminar at ETH. Additional details will appear soon….

(4) Finally, from June 17 to 21, in sunny Marseille, R. de la Bretèche, Ph. Michel, J. Rivat and myself are co-organizing a conference on Analytic Number Theory in honor of É. Fouvry’s 60th birthday. This will be held at CIRM, which is a also a very nice place indeed to do mathematics. The web page for the conference is here; registration to the conference should be done on the CIRM website (the registration form is not there yet).

January 14th, 2013 at 12:32 pm