Blog of Matthew Daws

Open source software

For various reasons relating to https://github.com/MatthewDaws/AccessibleLaTeX I have ended up down a rabbit-hole of trying to understand Open Source Software Licenses, and related ideas, like Creative Commons. These are some notes for my own memory if nothing else.

26th July 2020

Stalled work

Cleaning out my desk, I came across some plans for further work on predictive policing. It now seems rather unlikely I will have time to pursue these (what with a fixed number of hours in a day, and a desire to be a research in Mathematics, at least at the moment). I thought I might as well record the ideas here.

17th June 2020

Notes

A couple of new research notes:

Some notes on inductive limits of Banach spaces and algebras. I don't have a use for this rather esoteric topic, but a couple of textbooks make (slightly) wrong claims, so I wrote up some notes and carefully checked how far we could get things to work.
A quick proof showing how to get the Kaplansky Density Theorem by using Arens products, and "elementary" (for various values of elementary) \( C^* \)-algebra theory.

9th June 2020

Maps

Because of lockdown, and the desire to occasionally get out the house, I have been exploring the local area more closely. The following are some nice resources:

StreetMap.co.uk : Online access to OS maps of various scales.
Rights of way in Calderdale : You cannot see the "definitive map" online, but...
Leisure and culture map : Gives a "non-definitive" map. Seems the same as OS maps to me, but perhaps easier to check exact details on.

9th June 2020

TALMO

I've spent yesterday afternoon and this morning attending the TALMO conference, from the comfort of my home office, via Zoom. The extremely efficient organisers have already got many of the presentations uploaded to YouTube.

Some links which I made during the talks:

OBS Virtualcam : OBS is a great (free) screen recorder which allows e.g. composing different inputs (so overlaying a webcam image at an arbitrary place in a screen capture of just one window). The "Virtualcam" is an output which fakes up a new webcam on your system, hence allowing you to pipe the OBS output into any application which uses a webcam.
Accessibility talk slides : This has been rumbling away in the background, but an unhappy confluence of a looming deadline just as we add more things online makes it more important. Particularly discussed was Bookdown. Perhaps it is time to move all my lecture notes to a new format. But it's the input of time required, and a new toolchain to learn...
Xournal++ (a fork of Xournal into C++ I think leads to the title) is a FOSS PDF annotator that supports LaTeX. Next time I am marking work I will investigate this.
There was a question asking about Tablets. Suggestions included Wacom tablets, and those by xp-pen
Videos to help students adapt from A-Levels which is especially important this year, as most students will have missed the end of their A-Level studies. There was some talk that the AMSP would be doing something, but I couldn't find much (at a brief glance).

3th June 2020

Genetics and ancestry

What feels like a lifetime ago (before some other genetics happened) I listened to Adam Rutherford's book of the week "How to Argue With a Racist" on Radio 4. It's now been so long that the Radio 4 link is dead, but you can buy the book or read the book review. The radio series was interesting, but one particular (slightly off topic) point I remember. Adam claimed (I mean, I think, it was a while ago) something like

Go back around 11 generations, and you will have ancestors who share none of your genetic material.

What argument might lead to this conclusion? My main initial conclusion was that I did not really know how inheritance works at the genetic level.

17th May 2020

DJVU and PDF

Some notes to myself on working with DJVU and PDF.

To convert a DJVU file to PDF:

Download djvulibre for windows.
Use ddjvu.eve -format=pdf -page=1-10 infile.djvu outfile.pdf
Manual: http://djvu.sourceforge.net/doc/man/ddjvu.html Notice in particular docs about quality, using JPEG compression etc.
Source: https://superuser.com/a/571787/503838

18th April 2020

New preprint

Well, not new really, just I forgot to blog about it. "Ring-theoretic (in)finiteness in reduced products of Banach algebras" with Bence Horváth (currently a postdoc at the Czech academy of sciences). Available at arXiv:1912.07108 [math.FA]

We look at ultrapowers and the asymptotic sequence algebra of Banach algebras. There has been some interest recently in using tools from Model Theory (specifically, the recent area of "Continuous model theory") to study such objects for \( C^* \) and von Neumann algebras. One of our research themes is that things do not work so nicely for Banach algebras, and in particular, one often has to get one's hands dirty (and not use Model Theory results) because Banach algebras are not very "metrical" objects, unlike operator algebras. We construct various counter-examples, and also leave open some tantalizing questions about renormings of some rather concrete algebras.

I worked (in a very "bare hands" way) on ultraproducts in my thesis, and shortly afterwards, and it was fun to return to this topic, but to take a slightly more abstract approach. Something we wrote in the introduction is that we wonder if the asymptotic sequence algebra of a Banach algebra could be an interesting source of (counter-)examples for other problems?

25th February 2020