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Tom de Jong

@de-Jong-Tom.mathstodon.xyz.ap.brid.gy
51 followers 2 following 97 posts

Postdoc at Radboud University, previously at University of Nottingham, working on type theory. PhD from University of Birmingham. Mathematician, computer […] 🌉 bridged from ⁂ mathstodon.xyz/@de_Jong_Tom, follow @ap.brid.gy to interact

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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 16/10/2026
Benedikt Ahrens, who co-supervised my PhD, has funding for a PhD position at TU Delft 🙂️ I'm copying his ad below. I highly recommend both Delft and Benedikt! #TypeTheory #Agda #CategoryTheory #PhD ---------- I am looking for a PhD candidate for a 4-year position in the Department of Software […]
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Gro-Tsen @gro-tsen.bsky.social · 12/10/2026
English translation of an email I sent to a student worried about the future of mathematics: ⬇️ (French original is in the quoted post)
Excerpts: «
In any case, I fully agree with what you wrote (and your email shows that you grasp the situation very well).  I, too, am convinced that AI companies do not care about science; if they did, they would have provided more details — for instance, regarding the full range of problems they attempted to solve, the methods employed, and so on.  They simply want to train and sell their models; they have chosen mathematics as a battleground and a training ground, and this is causing immense harm to science.  I also reject the vision of mathematics turning into a “sort of 'math vibing', where you have to decipher what a computer has compiled, churned through, and spewed into a file” — as you so eloquently put it.

[…]

I don't know how it will all turn out, so I certainly can't promise you anything.  But I do know that “understanding” is a human activity — something computers cannot do for us (even if they solve problems better than we do, it serves no purpose unless there are humans who actually understand).  Perhaps mathematical research will shift its focus toward the pursuit of interesting questions, illuminating perspectives, or elegant exposition (including aimed at the general public) rather than the race to answer difficult problems; that is what I hope for.

[…]

So, I cannot make any promises to you on what will happen tomorrow.  Clearly, you have a very good grasp of the current challenges (better than some of my fellow researchers).  I would fully understand if you decided to leave mathematics for another field […] — after all, the very purpose of this program is to enable you to decide what you prefer and what you find most interesting and useful.  But what I can say with certainty is that if the advent of AI discourages promising students from pursuing mathematics, that will be the greatest harm it has done to the discipline.
»
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 05/10/2026
[1] André Joyal. Notes on clans and tribes. arXiv:1710.10238, 2017. [2] Michael Shulman. All (∞,1)-toposes have strict univalent universes. arXiv:1904.07004, 2019. [3] Benno van den Berg and Ieke Moerdijk. Exact completion of path categories and algebraic set theory: Part I: Exact completion of […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 05/10/2026
We propose a new approach to the semantics of identity types in intensional Martin-Löf type theory. The setting is quite general, assuming only a category with finite limits and an exponentiable interval. It therefore applies to many different cases such as clans [1], model categories [2], path […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 05/10/2026
This week the #HoTTEST seminar presents: Steve Awodey Path types in Algebraic Type Theory The talk is at 11:30am EST (16:30 UTC) on Thursday, October 8. The talk will be 60 minutes long, followed by up to 30 minutes for questions. See hottest-seminar.github.io for the Zoom link and a […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 01/10/2026
During those 8 years I maintained strong ties to the Netherlands, largely because my partner continued to live there. As a result, I've long felt that I was living two lives. This was rich and fun, but also (increasingly) exhausting. I feel very fortunate that I was able to "go home" while […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 01/10/2026
Eight years ago, I moved to the UK to do a PhD within the Theory (Computer Science) group of the University of Birmingham, supervised by @MartinEscardo and co-supervised by Benedikt Ahrens. After my PhD, I moved to Nottingham's Functional Programming (FP) Lab to work with @Nicolai_Kraus. I […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 01/10/2026
I've started my new job! As of today, I'm a postdoc in the Software Science group of the Institute of Computing and Information Sciences at Radboud University in the Netherlands. This position is (largely) funded by a personal 3-year Veni fellowship from the Dutch research organization NWO. I'm […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 19/09/2026
The slides for my course in homotopy type theory / univalent foundations at the Proof and Computation autumn school are available at: tdejong.com/talks/PC-2026-1.pdf tdejong.com/talks/PC-2026-2.pdf tdejong.com/talks/PC-2026-3.pdf As always it was a great pleasure to be a […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 18/09/2026
[LLMs] I'm not big on legalese but nevertheless I found this court document [1, found via [2]], and the quotes from people in the tech industry, quite interesting. Example: "Microsoft has observed that “threaten[ing] the economic foundations of its essential […] [Original post on mathstodon.xyz]
Picture from a Microsoft document with the caption "Argument from Data Leverage literature: We tech folks might think we're the entire world, but content creators are Archimedes."
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 09/09/2026
RE: mathstodon.xyz/@de_Jong_Tom/1159326… And now this paper with @MartinEscardo on injective types is published in the Annals of Pure and Applied Logic 🙂️ doi.org/10.1016/j.apal.2026.103829
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 15/08/2026
RE: mathstodon.xyz/@de_Jong_Tom/1168962… Teaching homotopy type theory in just 5 lectures was certainly a challenge, but also a hugely enjoyable one! Many, many thanks to all that attended and their lovely questions! I had a fantastic time in Prague where I also enjoyed […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 15/08/2026
RE: links.bouncepaw.com/2290 This was a fun read
links.bouncepaw.com
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 13/08/2026
Who came up with the "type check" vs "vibe check" joke? The students in my HoTT course liked it, and I also like it a lot (and it's actually useful in some explanations). But I would like to remember who came up with it, so that I can give them credit in the future.
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 09/08/2026
Made to Prague for #ESSLLI! The hotel room TV remote is interesting 😄
A remote with a lambda on the bottom left.
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Gro-Tsen @gro-tsen.bsky.social · 07/08/2026
I asked a long question on MathOverflow about which topos best represents L. E. J. Brouwer's ideas on intuitionism (some of which I have tried to summarize): mathoverflow.net/q/514026/17064
mathoverflow.net
Which topos (or topoi) most accurately reflect Brouwer's ideas on intuitionism?
Let me first clarify that I am not expecting the titular question to have a single well-defined answer (or it would probably have to be a useless one like “the topos freely generated by the followi...
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 03/08/2026
Just learnt that our paper "A study of Kock's fat Delta" (arxiv.org/abs/2503.10963) with Nicolai Kraus (@Nicolai_Kraus), Simona Paoli and Stiéphen Pradal (@Stiephen) was accepted for publication in the Journal of Pure and Applied Algebra (JPAA). I'm quite happy about this, but I'm […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 23/07/2026
One of the joys of using #Typesetter (a minimal editor for #typst) is that I find it improves after each update which is not usually the case for many other pieces of software 🥲️
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Andrej Bauer @andrejbauer.mathstodon.xyz.ap.brid.gy · 15/07/2026
I was invited to speak at the Summer Conference on Topology 2026and its Applications in Split, Croatia. This is how I tried to explain the topos of countable reals to ordinary topologists: www.andrej.com/assets/slides/topolo… I did get a bunch of […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 14/07/2026
@jeanas You can't (I think).
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 10/07/2026
The teaching materials (first version) for my course "Introduction on Homotopy Type Theory / Univalent Foundations" at ESSLLI 2026 are now available at github.com/tomdjong/ESSLLI-2026 I really enjoyed putting this together and naturally I (re)learnt a thing or two myself in the […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 22/06/2026
This week I'm very much looking forward to the "Formal proof and synthetic mathematics" workshop co-organized by @matematiflo! matematiflo.github.io/ProofWorkshop… Can't say the same about the weather forecast...
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 14/04/2026
I'm on the PC of Computer Science Logic (CSL 2027). csl2027.github.io The abstract/paper submission deadlines are 8/15 July 2026 (AoE) with notification of accepted papers on 15 October 2026, and the conference itself on 25-29 January 2027 in Brighton. I would love to see papers on […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 14/04/2026
I'm on the PC of Computer Science Logic (CSL 2027). csl2027.github.io The abstract/paper submission deadlines are 8/15 July 2026 (AoE) with notification of accepted papers on 15 October 2026, and the conference itself on 25-29 January 2027 in Brighton. I would love to see papers on […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 04/06/2026
The 37th European Summer School in Logic, Language and Information (ESSLLI), taking place from August 3rd to August 14th, 2026 at the Faculty of Civil Engineering, Czech Technical University, Prague, Czechia. 2026.esslli.eu = Overview = The European Summer School in Logic, Language and […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 04/06/2026
RE: mathstodon.xyz/@de_Jong_Tom/1164356… The early-bird registration deadline for the European Summer School in Logic, Language and Information (ESSLLI) has been extended to 15 June. 2026.esslli.eu/registration/registr… [More details in the reply to this post.]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 03/06/2026
Does anybody know how to typeset pullback/pushout corners in typst/fletcher? The code provided at github.com/Jollywatt/typst-fletcher… does not quite work for me and even when it does, it requires experimenting with degrees which is bad. #typst […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 01/06/2026
RE: mathstodon.xyz/@iblech/116675413147… I didn't know of this collection of notes by (the late) Thomas Streicher. Thanks for sharing them! www2.mathematik.tu-darmstadt.de/~st…
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 15/05/2026
RE: mathstodon.xyz/@de_Jong_Tom/1160756… Application deadline: 1 June. This year's edition will be the 10th!
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 12/05/2026
RE: mathstodon.xyz/@de_Jong_Tom/1164356… Just over two weeks before early registration ends (31 May)!
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 09/05/2026
As usual, I was reading this weekend's De Volkskrant (Dutch newspaper) and amused to find @jonmsterling quoted in @ionica's column 🙂 (Minor correction to the column: Jon isn't British.)
Partial screenshot of Ionics Smeets' column (in Dutch) that quotes Jon Sterling.
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 08/05/2026
#TYPES 2026 is done! The slides for my talk are here: tdejong.com/talks/TYPES-2026.pdf. Joint work with @ljungstrom and @Nicolai_Kraus.
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 03/05/2026
On my way to Gothenburg for #TYPES. Please come and say hi!
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 23/04/2026
RE: social.edu.nl/@jaror/11645369030424… Quoting/Boosting for reach.
social.edu.nl
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 20/04/2026
Following @jaycech3n's beautiful PSSL 112 slides (drive.google.com/uc?export=download…) I tried out typst last week. Verdict: For papers, LaTeX (after all, I'll want to submit them). For anything else, typst.
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 20/04/2026
The 37th European Summer School in Logic, Language and Information (ESSLLI 2026) will take place on 3-14 August in Prague. 2026.esslli.eu I'm excited that I'll be teaching an introductory course on univalent foundations / homotopy type theory! @stringdiagram and @jaklt will also be […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 19/04/2026
RE: types.pl/@ncf/116427482324540411 Fun puzzle and a nice observation!
types.pl
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 17/04/2026
At 9.50 today, I'm giving a talk on constructive domain theory at the Formal Topology Workshop in Venice. Feat. a shoutout to @nmvdw and @dif for their nice paper "The Interval Domain in Homotopy Type Theory". It should be livestreamed: youtube.com/@wires0/streams Slides […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 16/04/2026
I'm pleased, especially for our PhD student @aref_mz, that our paper "Generalized Decidability via Brouwer Trees" (arxiv.org/abs/2602.10844) with @aref_mz, @Nicolai_Kraus and @fnf was accepted to LICS'26. #Agda was very useful for developing this work. Huge thanks to its maintainers! […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 13/04/2026
RE: mathstodon.xyz/@buchholtz/116397805… Me too! 😁
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 31/03/2026
Thanks to our speakers and @Stiephen all the slides for PSSL 112 are now available on the PSSL website! sites.google.com/view/pssl112/progr… #CategoryTheory #Logic
The participants of PSSL 112 are standing on a patch of grass in sunny conditions.
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 29/03/2026
I recently spent considerable time and effort subreviewing a paper (I could afford to). I'm really, really pleased to see that this was appreciated by the author and will lead to an improved paper.
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 28/03/2026
Paul Levy at PSSL 112: "Unfortunately... Or rather, sadly, there's no fortune when it comes to maths." Maybe I should dedicate my account to Paul Levy quotes.
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 20/03/2026
I had a great time at this Dagstuhl seminar on proof assistants and constructive/synthetic mathematics. Many thanks to the organizers Ingo Blechschmidt, Liron Cohen, Thierry Coquand, and Peter Schuster! www.dagstuhl.de/en/seminars/seminar… I gave a talk […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 07/03/2026
RE: mathstodon.xyz/@ayberkt/11617821363… And the recording is on YouTube: youtu.be/3jk1INJgcqs Thanks again, @ayberkt!
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 04/03/2026
The program for the 112th Peripatetic Seminar on Sheaves and Logic (PSSL 112) is up on the website sites.google.com/view/pssl112/progr… 17 talks on #CategoryTheory (and #TypeTheory) from a variety of speakers! If you'd like to attend please register by March 14th following the form on […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 03/03/2026
Abstract: I will present a constructive and predicative development of locale theory in HoTT/UF (j.w.w. Martín Escardó), with a particular focus on the theory of spectral and Stone locales. The traditional approach to the predicative development of point-free topology is to work with […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 03/03/2026
This week the #HoTTEST seminar presents: Ayberk Tosun (@ayberkt) Constructive and predicative locale theory in univalent foundations The talk is at 11:30am EST (16:30 UTC) on Thursday, March 5. The talk will be 60 minutes long, followed by up to 30 minutes for questions. See […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 20/02/2026
I'm on the PC of MFPS (Mathematical Foundations of Programming Semantics) this year. ul-fmf.github.io/mfps-sstt-2026/mfp… Please consider submitting a paper, especially if it's on constructive mathematics, domain theory, denotational semantics and/or (homotopy) type […]
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Tom de Jong @de-jong-tom.mathstodon.xyz.ap.brid.gy · 15/02/2026
The 2026 website for the annual autumn school Proof and Computation is now up at www.mathematik.uni-muenchen.de/~sch… I'm excited to give a short course introducing homotopy type theory / univalent foundations, and look forward to participating in this very enjoyable school […]
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