About

If you need to contact me privately, you can try
jacques dot gentzen at gmail dot com

I’m currently interested in logic, (semi-)lattice theory and universal algebra, but I expect this to be only temporary. I like good readable (medium level) German books on mathematical subjects I’m currently interested in. I currently like Dietlinde Lau: “Algebra Und Diskrete Mathematik 2: Lineare Optimierung, Graphen und Algorithmen, Algebraische Strukturen und Allgemeine Algebra mit Anwendungen”, Volker Diekert, Manfred Kufleitner, Gerhard Rosenberger: “Diskrete algebraische Methoden: Arithmetik, Kryptographie, Automaten und Gruppen”, and Heinz-Dieter Ebbinghaus, Jörg Flum, Wolfgang Thomas: “Einführung in die mathematische Logik”. I cite these books, because they managed to teach me advanced material, which I already tried to learn with less success before.

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The above text is from Dec 11, 2014. Before getting to the update, let me talk about vzn. He stopped talking to me, or to anybody else on the internet (in April, 2021). Nobody knows why. It is sad. One reason for starting this blog were his attempts to get the Community Blog for Mathematics Stack Exchange started, and to keep it alive. He knew that it is not easy to keep a blog running. My activity on Stack Exchange dropped significantly in 2020. I had switched from reviewing ambitious papers in my area of expertise to reviewing interesting ideas regarding physics and probability, after my reply to Lev Gordeev got rejected by the list moderator. And as an indirect consequence of this, I learned to enjoy Physics Forums. Therefore I decided to use my introductory message from Feb 4, 2021 (which is only visible to members) as my update to describe what I do currently:

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I am an applied mathematician working in semiconductor manufacturing. This means stuff like optical lithography, ebeam lithography, resist development processes, etching processes, optical metrology, scanning electron beam metrology, and other related physical or chemical processes. I do work with physicists on a daily basis, but I am not a physicist myself. I took that career path long ago because in my experience, establishing friendly relationships with physicists was easy.

However, that is not the reason why I am here. There recently was a thread Consistent Histories solipsism? in the Quantum Interpretations and Foundations subforum. I subscribed to be able to say some clarifying words about consistent histories, if needed. However, Morbert did a better job than I could have done at clarifying those misconceptions, so there was no need for me to get actively involved. I had tried to publicly defend and clarify consistent histories at one point before:

Around 2005, I read (or rather browsed) “Understanding Quantum Mechanics” by Roland Omnès, and it was the first time that I felt that the material was presented in a way that I would understand it, if I invested the time to work through it. It felt like “let me calculate and explain” as opposed to “don’t ask questions, nobody understands QM anyway”.

In hindsight, my more relevant contribution to that discussion (about consequences of the Frauchiger-Renner Paradox) was to mention Craig Gidney

I find Craig Gidney’s approach to distinguish between “before-hand experience” description vs. “in-the-moment experience” descriptions enlightening

who wrote The Frauchiger-Renner Paradox is a Sleeping Beauty Problem half a year later. For me, this is the most convincing resolution of the paradox I have read so far. Interestingly enough, Craig Gidney is not a physicist either.

I fear that if I will happen to make actual contributions here, the pattern will always be that I read something, that it convinced me at least in certain points, and that I will try to defend it at least with respect to the points that I did understand. But my experience tells me that I will probably always be late to the game.