I was slow blogging, and catching up won’t be so easy. Of course, this brings me back to the question of what I should blog about. Ideally, I should tell you about mathematical things I heard about. The problem is that it is hard to do so in real-time. I can also try to write about older things and indeed one of my next posts will be about a beautiful geometric proof of Micha Perles for a special case of the Erdos-Sos conjecture about trees. I can also tell you a little about where we were. (In reverse chronological order.)

### IMPA, Rio and Peru

Just came back from a splendid visit to Peru and Brazil with my son Hagai. In Brazil I took part in the 31st Brazilian Mathematical Colloquium which was a wonderful event with many young people and a great deal of enthusiasm for mathematics.

### Five-Puzzles lectures and papers

My talk at Rio was a general-audience personal tour across five mathematical puzzles that I encountered during my career. (Note to self: to write here about these puzzles.) In a second lecture I elaborated a bit more on the first puzzle and its connections to convexity. Apologies for my English. At least it seems that I am thinking before finally deciding to go with the wrong option, like “Did I succeed….ed” or “How come…s”

### Elisha Netanyahu memorial lecture

Earlier, I gave a similar talk at the Technion – the Elisha Netanyahu Memorial Lecture. It was fascinating to learn about Elisha Netanyahu whom I did not know personally. Before the talk a nice written greeting by Benjamin Netanyahu (Elisha’s nephew) was read.

### Discrete Geometry and Convexity

Imre Barany’s 70th birthday conference in Budapest was a very special event. And here is the playlist of the lectures and my lecture.

### IMU meeting in Acre

I try not to miss the annual Israeli Mathematical Union meeting. This year it was in Acre with some excellent plenary addresses and a really great session in discrete mathematics and theoretical CS that Nathan Keller and I organized. I plan to tell you about some of the results from our session later.

### More pictures and links

From the top: Happy days, a lecture by Einat Wigderson and me at AviFest (clique for the video). Implementing interior point methods, implementing the simplex algorithm (click for a video), two pictures from Machu Pichu; my quantum puzzle paper translated into Chinese, balancing a twister (click for a video), at IPAM with Yoshiharu Kohayakawa (Yoshi) and Rob Morris, and with Gugu (Carlos Gustavo Moreira); Hugo mentions KKL and BKKKL! (all talks of the probability school and Brazilian Colloquium are available on IMPA You Tube channel), with Ron Holzman and Nathan Netanyahu.

### The decline of confidence and ability with age.

When commenting on polymath projects and in other mathematical occasions I sometimes make silly remarks and even then I usually regard it as a positive contribution to the discussion. When I made this remark on poymath12, which turned out to be quite silly a few minutes later, I somehow lost my confidence a little and had a feeling of “losing it”. I was a little sorry about the matter but then my next thought about it was:

This is wonderful, because it will give us an opportunity to examine the decline of confidence and ability with age.

Well, the decline of confidence and ability with age, is overall sad, but arguably monitoring and understanding this phenomenon is important. I was later happier about other polymath12 comments and proposed directions, but the aging angle is something to keep in mind. (Disclaimers: This section is for entertaining purposes only; It follows a long tradition in combinatorics, Paul Erdos started complaining about old age when he was 28.)

## Great honors

Last but not the least, I am proud and happy to report on several important honors given to me. I was elected to the Israeli Academy of Science and Humanities, and also to the Academia of Europe, and as an honorary foreign member to the Hungarian Academy of Science. I was also chosen to give a plenary address at the 2018 ICM in Rio which is also a great honor and a great challenge. I am very happy and thankful for these unexpected honors.

A short Hebrew general-audience talk about (two and a half) puzzles at the Israeli Academy of Science and Humanities.

Alex Lubotzky and me are both invited plenary ICM 2018 speakers in Rio. In 2004 we explored Rio and Brazil together with our wives and in 1994 we were both invited speakers at the ICM in Zurich. Here we collaborate on a Clay foundation video describing (a little of) the mathematics of Larry Guth and Nets Katz. (Click on the picture for the video.)

**Update:** Let me make a quick update with additional links going chronologically even a few months backward. In 2016 I gave several lectures on quantum computers (explaining my research and analysis on why they are not possible). I gave a series of three lectures in Bloomington, Indiana in a very enjoyable trip (my second) to the department. Here are the slides of lectures (Lecture I: The quantum computer puzzle, Lecture II: Elections!, Lecture III: What can we learn from the failure of quantum computers.). At that same year I also gave the Pekeris lecture at the Weizman Institute again on quantum computers (Here are the slides, the first few slides are about Pekeris and connections of his work to quantum computers and to dating the earth). In 2016, I participated in a truly amazing conference celebrating the work of Jean Bourgain, and gave a lecture (here is the video) on questions I asked Jean along the years. (No quantum staff, I afraid.) Here is the full playlist. Here is, again the link to my plenary lecture at the 2016 European Congress of Mathematics (7ECM), and, I also found on-line my lecture from Noga fest (full playlist).

Also, here are the first slides for my Technion devoted to Elisha Netanyahu and his contemporaries and his Ph.D from our library.

Gil,

Is your position on reliable quantum computing in practice still the same as when you debated Harrow?

And I doubt that you giving a lecture at ICM can reasonably be called unexpected, given your past 🙂

Thanks, Kodlu, Yes, my position is the same as was in the debate with Aram. Actually puzzle number 4 in the lecture (28:10-49:10) is about the “quantum computer puzzle”. The relation to noise stability and low degree polynomials is a novel aspect of my analysis.