**A**lthough it went completely out of my mind, thanks to a rather heavy travel schedule, I gave last week a short interview about the notion of mathematical models, which got broadcast this week on France Culture, one of the French public radio channels. Within the daily *La Méthode Scientifique* show, which is a one-hour emission on scientific issues, always a [rare] pleasure to listen to. (Including the day they invited Claire Voisin.) The theme of the show that day was about the unreasonable effectiveness of mathematics, with the [classical] questioning of whether it is an efficient tool towards solving scientific (and inference?) problems because the mathematical objects pre-existed their use *or* we are (pre-)conditioned to use mathematics to solve problems. I somewhat sounded like a dog in a game of skittles, but it was interesting to listen to the philosopher discussing my relativistic perspective [provided you understand French!]. And I appreciated very much the way Céline Loozen the journalist who interviewed me sorted the chaff from the wheat in the original interview to make me sound mostly coherent! (A coincidence: Jean-Michel Marin got interviewed this morning on France Inter, the major public radio, about the Grothendieck papers.)

## Archive for France Culture

## La déraisonnable efficacité des mathématiques

Posted in Books, pictures, Statistics, University life with tags all models are wrong, Bayesian inference, foundations, France Culture, France Inter, Grothendieck, interview, M-open inference, Paris, philosophy of sciences, Radio France, statistical mathematics on May 11, 2017 by xi'an## round-table on Bayes[ian[ism]]

Posted in Books, pictures, Statistics, University life with tags Bayes factors, Bayesian Analysis, Bayesianism, Bureau international des poids et mesures, decision theory, evidence, France Culture, French book, game theory, Henri Poincaré, neurosciences, non-informative priors, relativity, subjective versus objective Bayes, Université Paris-La Sorbonne on March 7, 2017 by xi'an**I**n a [sort of] coincidence, shortly after writing my review on Le bayésianisme aujourd’hui, I got invited by the book editor, Isabelle Drouet, to take part in a round-table on Bayesianism in La Sorbonne. Which constituted the first seminar in the monthly series of the séminaire “Probabilités, Décision, Incertitude”. Invitation that I accepted and honoured by taking place in this public debate (if not dispute) on all [or most] things Bayes. Along with Paul Egré (CNRS, Institut Jean Nicod) and Pascal Pernot (CNRS, Laboratoire de chimie physique). And without a neuroscientist, who could not or would not attend.

While nothing earthshaking came out of the seminar, and certainly not from me!, it was interesting to hear of the perspectives of my philosophy+psychology and chemistry colleagues, the former explaining his path from classical to Bayesian testing—while mentioning trying to read the book Statistical rethinking I reviewed a few months ago—and the later the difficulty to teach both colleagues and students the need for an assessment of uncertainty in measurements. And alluding to GUM, developed by the Bureau International des Poids et Mesures I visited last year. I tried to present my relativity viewpoints on the [relative] nature of the prior, to avoid the usual morass of debates on the nature and subjectivity of the prior, tried to explain Bayesian posteriors via ABC, mentioned examples from The Theorem that Would not Die, yet untranslated into French, and expressed reserves about the glorious future of Bayesian statistics as we know it. This seminar was fairly enjoyable, with none of the stress induced by the constraints of a radio-show. Just too bad it did not attract a wider audience!

## Claire Voisin’s CNRS Gold Medal

Posted in pictures, University life, Wines with tags Claire Voisin, CNRS, CNRS Gold Medal, France Culture, Institut Universitaire de France, La Sorbonne, Stephen Zweig on December 27, 2016 by xi'an**L**ast week, I attended the award ceremony of the Gold Medal of the French Scientific Research Council, which may well be the most prestigious scientific award in the country. It was awarded this year to Claire Voisin who is a specialist in algebraic geometry.

While I ended up in the meeting by the chance occurrence of Jean-Michel Marin visiting me, it was an impressive event with great talks from Claire Voisin (with a poetic praise of the complex exponential) and the CRNS Head, Alain Fuchs, but also quite enjoyable and mostly a-political discourses from the two Ministers attending the ceremony, Najat Vallaud-Belkacem and Thierry Mandon, who both mixed quotes from classics with some appreciation of Claire Voisin’s work. Even if one may suspect that those discourses were not (completely) written by the speakers (even though Mandon went looking for a Zweig’s quote during the meeting and ended up reading it from his phone, which was clearly unrehearsed!), they were delivered with enough conviction to be, well, convincing!

The event took place in the Grand Amphithêatre de la Sorbonne, which looked much nicer in the evening than when I attended the IUF rentrée a few weeks ago. And the classic (19th) paintings on the walls of this part of La Sorbonne made the ensuing cocktail even more classy. (Not that we had any opportunity to mingle with the Ministers, who are most likely too risk-adverse to be drawn in potential debates on the status of [funding] French Academia and academics…)

An update: on the road to Normandy, to visit my mother, we listened to a one-hour interview of Claire Voisin on France Culture that was a very good layman introduction to the maths she works on. (In French only.)

## Le Monde puzzle [#845]

Posted in Books, Kids, Statistics with tags Académie des Sciences, Escher, France Culture, James Joyce, Katrin, Le Monde, Lewis Carroll, mathematical puzzle, neurosciences, neutrino, quark on December 21, 2013 by xi'an**Y**et another one of those Le Monde mathematical puzzles which wording is confusing to me:

Take the set of integers between 1 and 1000. endow all of them randomly with red or blue tags. group them by subsets of three or more (grapes). and also group them by pairs so that a switch can change the colour of both integers. Is it always possible to activate the switches so that one ends up with all grapes being multicoloured? Unicoloured?

**I** find it (again!) ultimately puzzling since there are configurations where it cannot work. In the first case, take a grape made of four integers of the same colour, reunited two by two by a switch: activating the switch simply invert the colours but the grape remains uni-coloured. Conversely, take two integers with opposite colours within the same grape. No mater how long one operates the switch, they will remain of an opposite colour, won’t they?!

**T**his issue of Le Monde Science&Médecine leaflet actually had several interesting entries, from one on *“the thirst of the sociologist for statistical irregularities*“—meaning that regression should account for confounding factors like social class versus school performances—to the above picture about weighting the mass of a neutrino—mostly because it strongly reminds of Escher, as I cannot understand the 3D structure of the picture—, to another tribune of Marco Zito informing me that “quark” is a word invented by James Joyce—and not by Carroll as I believed—, to an interview of Stanislas Dehaene, a neuroscientist professor at Collège de France and a (fairly young) member of the Académie des Sciences—where he mentions statistical learning patterns that reminded me of the Bayesian constructs Pierre Bessière discussed on France Culture—.

## Bayes on the radio

Posted in Books, pictures, Statistics, University life with tags Bayes theorem, Bayesian statistics, France Culture, frequentist inference, Henri Poincaré, Higgs boson, Nate Silver, physiology, radio, radio show, Science & Vie, Thomas Bayes, xkcd on November 10, 2012 by xi'an**I**n relation with the special issue of Science & Vie on Bayes’ formula, the French national radio (France Culture) organised a round table with Pierre Bessière, senior researcher in physiology at Collège de France, Dirk Zerwas, senior researcher in particle physics in Orsay, and Hervé Poirier, editor of Science & Vie. And myself (as I was quoted in the original paper). While I am not particularly fluent in oral debates, I was interested by participating in this radio experiment, if only to bring some moderation to the hyperbolic tone found in the special issue. (As the theme was “Is there a universal mathematical formula? “, I was for a while confused about the debate, thinking that maybe the previous blogs on Stewart’s *17 Equations* and Mackenzie’s *Universe in Zero Words* had prompted this invitation…)

**A**s it happened [podcast link], the debate was quite moderate and reasonable, we discussed about the genesis, the dark ages, and the resurgimento of Bayesian statistics within statistics, the lack of Bayesian perspectives in the Higgs boson analysis (bemoaned by Tony O’Hagan and Dennis Lindley), and the Bayesian nature of learning in psychology. Although I managed to mention Poincaré’s Bayesian defence of Dreyfus (thanks to the *Theory that would not die*!), Nate Silver‘s Bayesian combination of survey results, and the role of the MRC in the MCMC revolution, I found that the information content of a one-hour show was in the end quite limited, as I would have liked to mention as well the role of Bayesian techniques in population genetic advances, like the Asian beetle invasion mentioned two weeks ago… Overall, an interesting experience, maybe not with a huge impact on the population of listeners, and a confirmation I’d better stick to the written world!