Matroid theory at “La Vacquerie-et-Saint-Martin-de-Castries”

While John & Michael are in Irsee doing some finite geometry, I’m in the South of France at a matroid theory gathering organized in the tiny village of La Vacquerie-et-Saint-Martin-de-Castries which is high up on the Larzac Plateau in the South of France.

Picture of La Vacquerie

This may seem an unlikely place for a conference, but it is where one of the eminence grises of matroid theory, Henry Crapo, lives. Henry is an amazing and eclectic personality who lives in a wonderful house large enough to double as a personal conference centre that he calls Les Moutons Matheux. As the village (approximately 135 inhabitants) has no real shops, Henry engaged a personal chef who prepared amazing meals entirely from local “bio” produce.

As my family came with me, we chose to stay in the city of Montpellier in order to be near kid’s activities, sightseeing and shopping, and so I drove up to the plateau every day, which involved grinding up a winding mountainous road in 2nd or 3rd gear passing between  grape vines and through picturesque little villages with roads barely wide enough for a single car, let alone the school bus!

Anyway, along with the fun and frivolity, some matroid theory was actually accomplished. I talked about one of my favourite open problems, namely whether or not there is an upper-root-free interval for the characteristic polynomials of cographic matroids (aka the flow polynomial of a graph) or more generally, whether every proper minor-closed family of binary matroids that does not contain all graphs has an upper characteristic-root-free interval. Here are the slides from my talk (LaVacquerie2011).

The other main topic of discussion was our proposed matroid package for the computer algebra system Sage. After the last meeting in Wellington, Rudi Pendavingh and Stefan Van Zwam have worked really hard on it and now have a working “alpha-version” of the package. We’re just wondering now how to organize ourselves properly in terms of version control etc.

Anyway, now the conference is over, we leave France in a couple of days. It has been an interesting trip in many ways so I’ll finish this post with three good things about France and three bad things about France.

Three Good Things About France

Bread – beautiful beautiful baguettes and croissants that cost 75 eurocents each! I know Perth is expensive but why do croissants have to be TRIPLE the price of those in France? Actually all food in France is far far cheaper than in Perth.

Motorway Driving – a speed limit of 130kmh which really helped on the drive from Paris to Montpellier. Also it seems so sensible to have a speed limit that is dependent on road conditions (in rain, the limit drops to 110kmh).

The French – everyone (well, almost everyone) we met was relaxed and friendly and seemed to go out of their way to help us. Our mediocre French was welcomed everywhere, the market sellers and shop owners smiled at the kids, gave them cherries and generally made us feel welcome.

Three Bad Things About France

Problems with foreign credit cards – most automatic machines (but not all) would not take my credit card, even though it is a “chip and PIN” card. Many of them also don’t take notes, but only coins, including the ones selling train tickets at Charles de Gaulle. Caused me endless problems.

Pools requiring “bonnets” and “slips de bain” – most public swimming pools (including the two we tried – the Paris Aquaboulevard and the Montpellier Piscine Olympique) do not permit boardshorts and you have to wear skin-tight Speedos which are highly unflattering, especially after many of the afore-mentioned baguettes and croissants. I don’t even have any, and so had to buy them from the thoughtfully-provided vending machine – but I had to guess the size, and I guessed one size too tight. Ouch. Thankfully the Paris pool did not require us to wear bathing caps (bonnets) but the Montpellier one did! Another vending machine provided those for a couple of euros. I have no idea what the rationale for this is, but I noticed that the lifeguards spent 97% of their time yelling at teenagers to put their “bonnet” back on. Given that there were numerous ladies with long hair who simply wore their cap perched on top of a big bun, this seemed particularly pointless.

Montpellier Traffic – Imagine a beautiful car-free historic centre (thankfully, we are staying here) surrounded by a maze of difficult-to-navigate one way roads crammed with traffic. Then rip up a dozen of the most important roads to install a new tram line, and alter the one-way direction of another dozen to accommodate this. Randomly scatter an inadequate number of “detour” signs around the roadworks, but ensure that anyone (futilely) following the detour signs is kept guessing by not including the same destination on any two consecutive signs. I got lost every single time I left or returned from La Vacquerie!

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