Archive for Oaxaca

L’Armée Furieuse [book review]

Posted in Books, Travel with tags , , , , , , on December 9, 2018 by xi'an

“On dit que les Normands n’aiment pas beaucoup parler… Ce n’est pas qu’ils n’aiment pas parler, c’est qu’ils n’aiment pas répondre. Ce n’est pas la même chose.”

I picked this book by Fred Vargas at the airport mostly because the back cover mentioned Orbec a town near my hometown in rural Normandy. With a slight misspelling to avoid legal issues I presume. It made for a nice read in the long trip to Oaxaca even though it is filled with impossibilities and incoherences. The crux of the story is an interesting medieval myth called l’armée furieuse (the Wild Hunt) that tells of a spectral army crossing the North of France and picking dammed souls soon to die. The wild hunt is also called la mesnie or maisnie Hellequin, from the name of the Lord leading the spectral army. According to a English monk from a Norman monastery in the 1100’s. Myth that some in current era want to exploit to cover real crimes. As in the previous novels of Fred Vargas that I read there is an interesting undercurrent of exposing the machinery of a rural community, with highly unorthodox police officers. Not that I recognized much of my hometown atmosphere. And the Deus ex Machina represented by a local count [historically speaking, Orbec is only a barony] and the industrial plot were by far too implausible! (With a geographical inaccuracy of setting La Touques river nearby. And of mentioning a train station in Cernay, to end up on a very picky note.)

a la casa matemática de Oaxaca [reminiscence]

Posted in Mountains, Running, Travel, University life with tags , , , , , , , , , , on December 2, 2018 by xi'an

As this was my very first trip to the CMO part of CMO-BIRS, as opposed to many visits to BIRS, Banff, here are my impressions about this other mathematical haven, aka resort, aka retreat… First definitely a very loooong trip from Paris (especially when sitting next to three drunk women speaking loudly the whole trip, thankfully incomprehensibly in Russian!), with few connections between Mexico City [airport] and Oaxaca,  adding [for me] a five and a half hour stay over in the airport, where I experimented for the first time a coffin-like “sleep pod” hostel and some welcome rest. But presumably an easier access compared with Calgary for mathematicians from the South and East of the USA. And obviously for those Central and from South Americas.Then, contrary to Banff, the place for the Casa Matemàtica Oaxaca is for the time being essentially a permanently booked hotel, rather than a dedicated conference centre. Facilities are thus less attuned to visiting mathematicians, like missing real desks in bedrooms or working rooms. Still a nice with a very peaceful inner yard (and too small a pool to consider swimming). Actually facilitating interactions when compared with Banff: blackboards in the patios, tables outside, general quiet atmosphere (except for the endlessly barking dogs in the neighbourhood). Of course the huge difference in the weathers between both places does matter. Paradoxically (given the size of Oaxaca City), CMO is more isolated than BIRS, where downtown is a mere five minute walks, even in the middle of winter. Except for the occasional blizzard. But Oaxaca offers a fabulous food scene worth the longer trip!As for outdoors, there is also a swimming pool (Cina). And back streets to run on, even though the presence of stray dogs in about every road making running broken and haphazard (never run by a dog!, which is my rule since a tiny but angry dog bit my ankle in Caracas!). Running splits up hill a few times every morning was great training! There is furthermore the possibility of sport climbing in nearby San Sebastian de Tutla, as I experienced with Aventours, a local guiding company. And bouldering in an even closer gym.

over Mexico [jatp]

Posted in Mountains, pictures, Travel with tags , , , , , , on November 21, 2018 by xi'an

surprises in probability [book review]

Posted in Books, Statistics, Travel with tags , , , , , , , , , on November 20, 2018 by xi'an

A very short book (128 pages, but with a very high price!) I received from CRC Press is Henk Tijms’ Surprises in Probability (Seventeen Short Stories). Henk Tijms is an emeritus professor of econometrics at the Vrije University in Amsterdam and he wrote these seventeen pieces either for the Dutch Statistical Society magazine or for a blog he ran for the NYt. (The video of A Night in Casablanca above is only connected to this blog through Chico mimicking the word surprise as soup+rice.)

The author mentions that the book can be useful for teachers and indeed this is a collection of surprising probability results, surprising in the sense that the numerical probabilities are not necessarily intuitive. Most illustrations involve betting of one sort or another,  with only basic (combinatorial) probability distributions involved. Readers should not worry about even this basic probability background since most statements are exposed without a proof. Most examples are very classical, from the prisoner’s problem, to the Monty Hall paradox, to the birthday problem, to Benford’s distribution of digits, to gambler’s ruin, gambler’s fallacy, and the St Petersbourg paradox, to the secretary’s problem and stopping rules. The most advanced notion is the one of (finite state) Markov chains. As martingales are only mentionned in connection with pseudo-probabilist schemes for winning the lottery. For which (our very own!) Jeff Rosenthal makes an appearance, thanks to his uncovering of the Ontario Lottery scam!

“In no other branch of mathematics is it so easy for experts to blunder as in probability theory.”  Martin Gardner

A few stories have entries about Bayesian statistics, with mentions made of the O.J. Simpson, Sally Clark and Lucia de Berk miscarriages of justice, although these mentions make the connection most tenuous. Simulation is also mentioned as a manner of achieving approximations to more complex probabilities. But not to the point of discussing surprises about simulation, which could have been the case with the simulation of rare events.

Ten most beautiful probability formulas (Story 10) reminded me of Ian Steward 17 formulas that changed the World. Obviously at another scale and in a much less convincing way. To wit, the Normal (or Gauss) density, Bayes’ formula, the gambler’s ruin formula, the squared-root formula (meaning standard deviation decreases as √n), Kelly’s betting formula (?), the asymptotic law of distribution of prime numbers (??), another squared-root formula for the one-dimensional random walk, the newsboy formula (?), the Pollaczek-Khintchine formula (?), and the waiting-time formula. I am not sure I would have included any of these…

All in all this is a nice if unsurprising database for illustrations and possibly exercises in elementary probability courses, although it will require some work from the instructor to link the statements to their proof. As one would expect from blog entries. But this makes for a nice reading, especially while traveling and I hope some fellow traveler will pick the book from where I left it in Mexico City airport.

Oaxaca sunrise [#2]

Posted in Mountains, pictures, Running with tags , , , , , , , on November 15, 2018 by xi'an

sunrise in Oaxaca [#1]

Posted in Statistics with tags , , , on November 12, 2018 by xi'an

off to Oaxaca! [workshop 18w5023]

Posted in Mountains, pictures, Statistics, Travel, University life with tags , , , , , , , , , on November 10, 2018 by xi'an

This morning I am off to Oaxaca, Mexico, for a week-long workshop which aims at bringing together a mixed audience of statisticians who are using and developing computational methods, researchers involved in computational statistical mechanics and its applications (e.g., materials science, biophysics), and applied mathematicians studying numerical methods used in the field of application from a mathematical viewpoint. As a co-organiser, with Gabriel Stolz and Luke Bornn, I hope that the workshop will truly see the start of a pragmatic cross-fertilization between fields through the exchange of ideas and methods such as research lectures, discussions, and practical sessions based on benchmark systems. This is also my first time at the Casa Matemática Oaxaca, as opposed to my several stays at BIRS, and I am quite excited to discover the place (although the workshop will take place in an hotel as the conference facilities are still under completion after that many years!) and the surroundings. (This is also my second visit to Mexico after the ISBA conference in Cancún in 2014.)