free Tuna Altinel

Tuna Altınel, an associate professor of mathematics at University Claude Bernard Lyon 1 since 1996 and a member of Institut Camille Jordan, was incarcerated by the Turkish authorities on Saturday 11 May, 2019. Internationally recognized as a mathematician, he is also a professor who stands as a model in clarity and dedication. He is also involved in the defence of human rights through the “Academics For Peace” movement.

Tuna Altınel is being prosecuted by the Turkish justice system for signing a petition entitled “We, Turkish academics, will not be a party to this crime”, in January 2016. This petition denounced the intervention of Turkish military forces in the south-east provinces of Turkey since the summer of 2015 (UN HCHR report) and called for the resumption of talks in order to restore peace.

As he arrived in Turkey on 12 April during French academic recess, his passport was confiscated. He was then arrested and incarcerated on Saturday 11 May. In February 2019, he participated in a public meeting—organized by an association legally recognized in France—, aiming to raise awareness about the consequences of military intervention on the civilian populations. His participation in that meeting appears to be one of the charges held against him.

Sign the petition

non-uniform Laplace generation

This year, the French Statistical Society (SFDS) Prix Laplace has been granted to Luc Devroye, author of the Non-Uniform Random Generation bible. among many achievements!, prize that he will receive during the 2019 meeting in Nancy, this very week.

ABC with Gibbs steps

With Grégoire Clarté, Robin Ryder and Julien Stoehr, all from Paris-Dauphine, we have just arXived a paper on the specifics of ABC-Gibbs, which is a version of ABC where the generic ABC accept-reject step is replaced by a sequence of n conditional ABC accept-reject steps, each aiming at an ABC version of a conditional distribution extracted from the joint and intractable target. Hence an ABC version of the standard Gibbs sampler. What makes it so special is that each conditional can (and should) be conditioning on a different statistic in order to decrease the dimension of this statistic, ideally down to the dimension of the corresponding component of the parameter. This successfully bypasses the curse of dimensionality but immediately meets with two difficulties. The first one is that the resulting sequence of conditionals is not coherent, since it is not a Gibbs sampler on the ABC target. The conditionals are thus incompatible and therefore convergence of the associated Markov chain becomes an issue. We produce sufficient conditions for the Gibbs sampler to converge to a stationary distribution using incompatible conditionals. The second problem is then that, provided it exists, the limiting and also intractable distribution does not enjoy a Bayesian interpretation, hence may fail to be justified from an inferential viewpoint. We however succeed in producing a version of ABC-Gibbs in a hierarchical model where the limiting distribution can be explicited and even better can be weighted towards recovering the original target. (At least with limiting zero tolerance.)

logicomix redux

I had not made the link until the last speaker of the 50 years of Dauphine commemoration was introduced that he was one of the authors of Logicomix. He spoke of the mathematical modeling of neurons and brain activity, rather than comics, but at a very low level that he called cartoonesque. It is a rare event that cartoon characters can be met in the flesh!

along Avenue Karl Marx [jatp]

la peste gagne…

(Source: Le Monde, 27 Mai 2019)

And in a more balanced presentation:

(Source: Le Monde, 27 Mai 2019)

ABC in Grenoble, 19-20 March 2020

The next occurrence of the “ABC in…” workshops will take place in Grenoble, France, on 19-20 March 2020. Both local organising and international scientific committees have been constituted and the program should soon be constructed, along with calls to contributions launched at the same time. As in most earlier versions of the workshops (ABC in Paris, London, Roma, &tc.), we are aiming at a workshop atmosphere and, thanks to local sponsors, the registration fees if any will be low.

Grenoble can be easily reached by fast trains from Paris, Roissy, Geneva and Lyon. (There are also flights to Grenoble airport from Warwick, as well as Bristol, Edinburgh, London, Manchester, Rotterdam, Stockholm, Warsaw, but this is less convenient than flying to Lyon Saint-Exupery airport and catching a fast train at the airport.) To add to the appeal of the place, the workshop occurs during the skiing season, with three mountain ranges in the close vicinity. Making ABski a genuine possibility for the weekend after!