A Topological Representation Theorem for Tropical Oriented Matroids

In April my paper “A Topological Representation Theorem for Tropical Oriented Matroids” with the main result from my PhD thesis has finally been published by JCTA (Journal of Combinatorial Theory Series A) :-).

git commit hook: Morse Code translation

I am very much in favour of version control systems to keep documents like papers, lecture notes, exercise sheets, … basically everything in.

This is the story of how I tried to convince/train a colleague to write sensible commit messages — which resulted in the probably least useful commit hook ever.

A few weeks into the semester, git log repeatedly showed me the following message:


My complaining about vacuous commit messages resulted in these:


    mehr bla

Several complaints later:


       .                   .

    .   .                   .

    ..-. .. -. .- .-.. ...- . .-. ... .. --- -. --- ..-. - .... .. .-. -.. ... .

Now hang on… The last one was different! And it went on like that:

    ...- --- .-. ... -.-. .... .-.. .- --. ..-. ..- . .-. .- ..- ..-. --. .- -..

    -. --- -.-. .... . .. -. ...- --- .-. ... -.-. .... .-.. .- --.

Since reading Morse Code nowadays seems like an utterly useless skill, I decided to have a commit hook do this for me.

It is written in Python and adds the translation of the Morse Code (or anything that looks like Morse Code) to the end of the commit message.
You can download it here.

With the first version the commit messages looked as follows:

commit e2af21c6b64bb0d5db1447c92879db4c4c9524f6
Author: Silke Horn

    -- --- .-. ... .  -.-. --- -.. .  .... --- --- -.-
    morse code hook

commit 2d614cce719bebb17798cbf9fcf55157da513e21
Author: Silke Horn

    .. ..-.  - .... .  -- --- ..- -. - .- .. -.  .-- --- -. .----. -  --. .-. --- .--  ..- .--.  -- ..- .... .- -- -- .- -
    if the mountain won't grow up muhammad has to write a hook

I convinced my colleague to install the hook; now the messages were once again easy to read. Unfortunately their content quickly went back to the likes of “bla” and “bla bla”.
So we were back to square one..

Logo: Discrete Mathematics and Geometry

Mittlerweile ist der Professor der Arbeitsgruppe “Algorithmic Discrete Mathematics” der TU Darmstadt an die TU Berlin gewechselt und hat eine neue Version des Logos bekommen.

New polymake startpage

Today the new polymake startpage went online with a clearer and simpler layout (See here for the old one.) and a set of funny pyramidal icons.

Extending polymake db research team news

Remap Keys on the Kensington Presenter

The Kensington Presenter is my favorite tool for presentations and a simple hack makes it even cooler. Besides a laser pointer, a forward and backward button it has this fourth button (the one with the square) that does not seem to do anything useful. In fact, it sends the key code for “b”, which switches of the screen in Skim (and Keynote, I think) but is not entirely useful elsewhere.


In some programs (like Terminal or Maple, in our case) one might want to remap this button to Return.

Since I could not easily find the instructions anywhere, I’ll post them myself.
Here’s what worked for me on Mac OS:

Install the software KeyRemap4MacBook. This already has quite an extensive list of presets. But we are going to define our own.
Once you installed KeyRemap4MacBook (and restarted your computer if necessary), open the preference panel. In the tab “Misc & Uninstall” click on “Open private.xml”. Then replace private.xml by the following code:

<?xml version="1.0"?>


    <name>Kensington Presenter Square Key</name>
    <device_only>DeviceVendor::KENSINGTON, DeviceProduct::PRESENTER</device_only>
    <autogen>__KeyToKey__ KeyCode::B, KeyCode::RETURN</autogen>


You can also download the file here.

Next in the tab “Change Key” click the ReloadXML button. This should add a new item to the list, that you can check if you wish to activate it. It remaps the button with the square to Return.


Dolivo ONe

Zum Ultra-Marathon beim alljährlichen TU Meet&Move haben die Arbeitsgruppen Optimierung und Numerik ein gemeinsames Team gestellt — das Team Dolivo One: Dolivo wegen der Adresse in der Dolivostraße, One, weil’s noch ein Team aus demselben Gebäude gab.

Dafür mussten auch neue T-Shirts her — vorne mit den Logos der vier beteiligten Arbeitsgruppen, hinten mit einem Bild von unserem Gebäude in der Dolivostraße.

AMS Math Subject Classification

Tropical geometry in the MSC2010:

14Txx Tropical geometry [See also 12K10, 14M25, 14N10, 52B20]
14T05 Tropical geometry [See also 12K10, 14M25, 14N10, 52B20]
14T99 None of the above, but in this section

Blaue Kreide

Wenn man, einige Jahre nachdem man die Schulzeit hinter sich gelassen hat, mit Studienanfängern zu tun hat, merkt man plötzlich, dass man nicht nur älter geworden ist…

Als ich im Vorkurs beim Erklären der komplexen Zahlenebene zur Illustration eine komplexe Zahl mit blauer Kreide in das Koordinatensystem zeichnete, wurde es schlagartig laut hinter mir. Ich hielt kurz inne, fragte mich, was gerade passierte. Normalerweise, wenn es im Hörsaal plötzlich laut wird, heißt es, dass Dinge unklar sind. Soviel hatte schon gelernt. Aber was sollte denn bitte an einer komplexen Zahl unklar sein?

Also drehte ich mich um und sah folgendes: 100 kleine Ersties kramen in ihren Mäppchen nach einem blauen Buntstift.


In der Sprechstunde zur Einführung in die Optimierung:

Assistent: “Schlupfvariablen… Woran erinnert euch das denn?”
Studentin: “Schlumpf!”




Here’s what you get for handing in unstapled homework:


This wonderful piece of art was created by my HiWi in the linear algebra II course.