Archive for Polytechnique

yet another French paradox

Posted in University life with tags , , , , , , , , , on October 30, 2011 by xi'an

Due to a new law introduced last May by the French government, it has now become almost impossible for foreign non-EU students who graduate from a French business (e.g., HEC or ESSEC) or engineer (e.g., Polytechnique) school, or from a university, to get a job in France after graduation, even with a firm offer from a company. (This post may sound like a strange complaint since, in some countries, a student visa prohibits its holder to get a permanent job without first exiting the country. But this was not the case in France till last May.) Indeed, those non-EU (post)graduates with a job offer need to apply to local administrations who decide whether or not the job fits a need and whether or not it could not be offered to a French national. (As if those local administrations had the proper expertise.) The procedure takes months, during which the (post)graduates cannot work. Months for no reason other than the administrations being understaffed. And in most cases the answer is no. Meaning these (post)graduates then have to leave the country within a month. And cannot apply to a student visa without first leaving the country…

This sudden change of policy has been heavily discussed in the national and international press (chinese version), on blogs, and by student and professional organisations: I cannot but join the flow of protests against this iniquitous, absurd, and counter-productive action, dictated by electoral motives catering to the rightmost (or just plain xenophobic) part of the electorate. It is counter-productive in that most of those students have been trained in elite public schools, meaning their training has been mostly supported by the State (i.e. the French taxpayer), which would only benefit from the input of highly qualified (post)graduates to the French economy. It is absurd in that those non-EU (post)graduates number in the thousands, hence are unlikely to make a dent in the immigration figures used to frighten the electorate. It is counter-productive because it sends the wrong message to potential students abroad and will thus lower the attractivity of French higher education, an attractivity which is already under pressure from competing countries like Canada and Australia (which just went ahead of France in terms of foreign students). It is absurd since the [former Education and currently Budget] Minister, Valérie Pécresse, has publicly written to the Minister of Interior to ask him to abolish a procedure “going the wrong way”. It is counter-productive because these students graduate from schools (HEC, Polytechnique, Essec, Mines, Ensae, &tc.) where there are more job offers than candidates with the proper training. So the typical xenophobic rethoric of “foreigners stealing jobs from nationals” falls completely off the mark there, even though it was instrumental in passing this law… Now, it is quite probable this law will not survive the elections next May, but le mal sera fait (in terms of attractivity)… Note that postdocs are not impacted by the procedure!

ABC à l’X [back]

Posted in Statistics, University life with tags , , , , on February 9, 2011 by xi'an

“It is difficult to ensure that such sophisticated battles against the ‘ε-dilemma’ that arise in the simulation based inferential approaches of ABC and ALC do not confound the true posterior.” Shainudin et al., 2010

It was a very interesting talk that took place at Polytechnique last afternoon. 9Although one could argue that the title was misleading in that ABC was never truly used, except as a scarecrow!) Indeed, Razeesh Shainudin gave a lively one-hour lecture where he showed that, for the standard Wright-Fisher coalescent model, the exact likelihood of the site-frequency-spectrum statistic (SFS). Ìt would have required much more time to cover the dense material contained in the paper he coauthored on this topic (and to appear in the Bulletin of Mathematical Biology, Algebraic Biology Special Edition), but his message was quite clear, namely that a graph analysis of the distribution of the SFS statistic was permitting a closed-form representation of the likelihood. And similarly for some linear combinations of the SFS that allowed for [great!] Kemeny and Snell‘s (1968) lumpability criterion to apply, namely for an impoverished Markov chain defined on an aggregated state space to remain Markov. I do see the direct consequence on the quality of ABC (except when conducting Monte Carlo experiments to compare both outputs) and I have not thought long enough to spot the impact on our current research, but appreciated very much the intuition given in the talk. The idea beyond the method seems to be that improving the support of the importance sampling distribution in order to remove parameter values that could not lead to the real data (SFS) provides a clear efficiency improvement)

Professor position at ENSAE/CREST

Posted in Statistics, University life with tags , , , , , on February 1, 2011 by xi'an

My graduate school of Statistics, ENSAE (which is associated with my research lab CREST) calls for applications for the position of Assistant or Associate Professor in Statistics/Mathematics, starting in September 2011. The complete description of the position is there and the deadline is February 20. The school is currently located in Paris but should move to the Polytechnique campus within three years.

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