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## Updating SVN on Mac OS X

When I tried to update a local copy of a SVN repository I got an error message similar to “This client is too old to work with working copy…”. I went to http://www.wandisco.com/subversion/download#osx I clicked on: “Mac OSX 10.9 – Mavericks – Subversion 1.9.2 – Client Only” There I gave away my privacy and got a package. I launched it and in exchange for total control over my computer it installed svn 1.9. Pursuant to the last message displayed by the installation I opened a terminal window and created on the current (home) directory a file named “.profile” with the single line “export PATH=/opt/subversion/bin:\$PATH”. I closed the terminal and opened it again and the command “svn –version” confirmed that the new version was installed…

## My COre – une alternative à Dropbox?

La Direction des Services Informatiques a mis en place une alternative à Dropbox ouverte aux membres des laboratoires CNRS. Dans le principe, on ne peut qu’applaudir. Concrètement, après moins de deux jours d’utilisation, j’ai perdu la synchronisation avec mes fichiers, ce qui ne m’est jamais arrivé en cinq années avec Dropbox. Apparemment le service est planté…

## Measures of maximum entropy for surface diffeomorphisms

One expects measure maximizing the entropy (m.m.e.) to be especially “interesting”, especially for dynamics with “some hyperbolicity”. For instance, under some (hyperbolicity) assumptions, one expects them to determine all the aperiodic invariant probability measure (see this expository paper). By a theorem of Newhouse (1987) based on Yomdin’s theory, $C^\infty$ smoothness ensures the existence of some m.m.e.

Finite multiplicity is a harder question – often it can be solved only after a thorough understanding of the dynamics. It is a classical result for uniformly hyperbolic diffeomorphisms. I proved it in my thesis for $C^\infty$ interval maps with nonzero entropy (finite smoothness is not enough, even though Ruelle’s inequality shows that all ergodic measures with lower bounded entropy have lower bounded Lyapunov exponents).

Here, at the School and Conference on Dynamical Systems at ICTP, I presented the following answer to a long standing question of Newhouse:

Theorem (B-Crovisier-Sarig). A $C^\infty$ smooth diffeomorphism of a compact surface with nonzero topological entropy has finitely many ergodic measures maximizing the entropy.

You can see the slides here.

## Why Orsay?

Neuroscience tells us why Orsay is best:

confirm the superiority of Orsay to those places (you know who you are). I am not sure I believe their numerical estimates but it’s nice to pretend.

## Ewige Wiederkunft

1870, 1914, 1939, 2015???

former Treasury Secretary Timothy Geithner described in his memoir a 2012 meeting with the German finance minister Wolfgang Schäuble in which Mr. Schäuble showed something approaching enthusiasm for pushing Greece out of the eurozone…

If this counts as a victory for the European project, it is hard to imagine what a defeat would look like.

The New York Times, July 13th, 2015

## Plus jamais ça, encore une fois

Vous êtes à présent sous la protection des forces des Nations unies… Je ne vous abandonnerai jamais.

Général Philippe Morillon, commandant de la force de protection des Nations-Unies, mars 1993

Dans les jours qui suivent leur abandon par le contingent onusien, le 11 juillet 1995, 8.000 hommes et garçons sont exécutés par les forces serbes sous le commandemant du général Mladic.

Cet acte de génocide a été prédit et sera observé par les services de renseignements des puissances présentes.

Source

## Serveurs SVN

Subversion (SVN) est un outil informatique qui permet de gérer la collaboration sur des documents et en particulier des textes. Il automatise (jusqu’à un certain point!) la mise en commun des modifications et systématise l’archivage. Son utilisation nécessite un logiciel sur la machine de chaque collègue (“client svn”) mais aussi un logiciel (“serveur svn”) tournant sur une machine constamment connectée à internet.

Quelques serveurs publics que je connais:

1. Les services numériques de la PLM (plateforme mathématique en ligne de mathrice, accessible avec les identifiants PLM ou par invitation) – j’y ai rencontré des problèmes d’ouverture de mes projets mais les informaticiens de mathrice ont été très réactifs;
2. Au département de mathématiques d’Orsay, le serveur FOSA (accessible sur demande auprès du service informatique) –  j’ai arrêté de m’en servir après son arrêt de durée indéterminée.
3. La forge Enseignement supérieur et Recherche.

## Some information on using SVN with the PLM:

A. Using an existing repository

1. You should make sure that you have a svn (subversion) client installed on your computer. (I have svntortoise which does this through clicks but works only on windows). For basic concepts and terminology see this glossary.

2. Then create on your computer an EMPTY folder (let us call it your local folder) where you want to work (don’t put your work there yet). Make this your current folder.

3. If your svn client accepts line commands, you should execute (usually in a linux terminal/window):

svn checkout https://svn.math.cnrs.fr/YOUR-REPOSITORY-NAME

When you do so, you will be prompted for identification – these are your PLM’s identifiers. Hopefully, your svn client will connect to the svn server on the PLM and copy everything in the repository (“depot”) into the current (empty) folder.

4. You can then overwrite the file “perturbation-lemma.tex” in your local folder using the one you worked on.

When “publish” (for Sylvain and me) your modifications, you should execute (in your local folder)

svn commit -m “brief description of the changes” .

(the final dot means that all modified files selected for versioning by svn are transfered).

the text after -m will be recorded for documentation.

5. When you want to update your local folder with what’s on the repository, you should execute (in your local folder)

svn update

6. When you create a new file (say newone.tex) in your local folder and you want it to be uploaded to the repository at the next commit you have to tell svn by executing (in your local folder):

## B. Managing repositories through the web interface

1. Logging on the web interface

– You should go to the page: https://portail.math.cnrs.fr/
– Click on the button (top right): connexion
– On the new page, click on the button “mon compte PLM”