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Dirk Lorenz

@dirque.bsky.social
1.1K followers 484 following 561 posts

Doing mathematics, also as a job. Now at Uni Bremen, was at TU Braunschweig. Only here for the math. Optimization, inverse problems, imaging, learning - stuff like that.

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Dirk Lorenz @dirque.bsky.social · 23/09/2026
Had a hard time grading seminar reports and presentations recently (you know, AI). Idea for next seminar: Give students papers I did not read (but would like to). They need to explain the paper to me (orally and in writing) and the grade is determined only by how good I understand.
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Dirk Lorenz @dirque.bsky.social · 23/09/2026
Signs that academia may be for you: * eduroam works on the first try * you get your travel reimbursement without having to email anyone twice * you understand your institution’s course management system
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Dirk Lorenz @dirque.bsky.social · 23/09/2026
Material decomposition with multispectral computed tomography still feels underresearched mathematically!Here is what Jürgen Jeschke and I came up with to better understand what is going on. arxiv.org/abs/2609.25926
arxiv.org
Enhanced attenuation modelling for multispectral computed tomography
We revisit the modelling of the material decomposition problem in multispectral computed tomography and propose to leverage the known absorption spectra of different materials. With this we both deriv...
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Guillaume @guillaume-garrigos.com · 20/07/2026
As I am preparing my calculus notes for next year, the resolution of the jacobian conjecture comes at the perfect time! Today I've learned a few things surrounding this result, which i'll gather in a thread 1/n
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Dirk Lorenz @dirque.bsky.social · 06/06/2026
Rebrand optimization as argmaxxing
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Sophie Huiberts @sophie.huiberts.me · 05/06/2026
George Dantzig died in 2005. Does anyone have any color photographs of him?
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Dirk Lorenz @dirque.bsky.social · 05/06/2026
Indeed! Also interesting that there was no urge to emphasize *human* computation or *human* calculation when it became possible that non-humans do these (or was there?)
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Société Mathématique de France @socmathfrance.bsky.social · 05/06/2026
The International Centre for Mathematical Sciences (ICMS, Edinburgh) is looking for a new Director. Application deadline is July 15. Please share this information with anyone who might be interested. icms.ac.uk/icms-seeks-n...
icms.ac.uk
ICMS seeks new Director - ICMS
ICMS seeks a new director as the tenure of our current Director, Minhyong Kim, comes to an end this summer.
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Dirk Lorenz @dirque.bsky.social · 03/06/2026
Every optimization problem is linear if you lift enough
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Dirk Lorenz @dirque.bsky.social · 02/06/2026
I noticed that LLMs already affect student presentations a lot, but now at #SIAMOP26 I realize that also here, people use ChatGPT et al. to produce their slides (at least, that's the obvious explanation for all the "Why this matters" boxes I see on slides...)
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Dirk Lorenz @dirque.bsky.social · 02/06/2026
That's a hell of a venue for a plenary talk here at #SIAMOP26
Photo of a very fancy old lecture hall from University of Edinburgh
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Dirk Lorenz @dirque.bsky.social · 15/04/2026
The exponential function has the remarkable property that it is the unique function f that satisfies the differential equation f'(x) = exp(x) with initial value f(0)=1.
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Dirk Lorenz @dirque.bsky.social · 21/03/2026
Everybody is dead. Chuck Norris is still alive.
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Dirk Lorenz @dirque.bsky.social · 16/03/2026
Modern technology makes conference evenings in the hotel much more enjoyable!
An electric guitar with a headphone amp in a hotel chair
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Dirk Lorenz @dirque.bsky.social · 07/03/2026
Prove that you are human - once and for all I can't get past level 4 🤖😬 neal.fun/not-a-robot/
neal.fun
I'm Not a Robot
Prove your humanity once and for all
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ISMP 2027 – Amsterdam @ismp2027.bsky.social · 27/02/2026
📢 #ISMP2027 comes to Amsterdam! The 26th International Symposium on Mathematical Programming will be held July 25–30, 2027. Join researchers from around the world to discuss advances, challenges, and opportunities in the theory and practice of mathematical optimization. 🔗 ismp2027.mathopt.nl #MOS
ismp2027.mathopt.nl
The 26th International Symposium on Mathematical Programming will be held in Amsterdam, The Netherlands, from July 25th through July 30th, 2027. The event is the symposium of the Mathematical Optimization Society (MOS).
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Dirk Lorenz @dirque.bsky.social · 02/03/2026
Am I right that a function that is not increasing and also not decreasing is in fact just creasing?
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Dirk Lorenz @dirque.bsky.social · 26/02/2026
So you tell me that when I call scipy's linprog with bounds=none, it uses a lower bound of zero?! Yeah, that makes a lot of sense #scipy!
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David K Butler @davidkbutler.bsky.social · 20/02/2026
I submit the following for the fifth derivative.
The letter y with a superscript that is four vertical tally marks with a fifth diagonal tally mark across them.
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Her Maths Story @hermathsstory.bsky.social · 20/01/2026
5 years ago today, Her Maths Story went live with our 1st story. What started as a small idea has grown into a global, supportive community celebrating #WomenInMaths. We’re deeply grateful to everyone who has shared, read, supported & believed in this journey. Here’s to the stories still to come 💛✨
A dark blue celebratory graphic marking the 5-year anniversary of Her Maths Story. The HMS logo appears at the top. Large white text reads “5 years” in the centre, surrounded by yellow star shapes. Additional text highlights milestones: 99 contributors, 200K website visitors, 194 countries reached via the website, and 4.9K followers across social media platforms.
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Dirk Lorenz @dirque.bsky.social · 19/01/2026
Universidad Técnica Federico Santa María in Valparaiso has a quite iconic campus tbh
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Dirk Lorenz @dirque.bsky.social · 31/12/2025
These tiles don't cease to amaze - with hexagonal holes you get a lot of symmetry!
Another periodic pattern with holes made of aperiodic tiles
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Dirk Lorenz @dirque.bsky.social · 28/12/2025
And they mix! 🧮 #mathsky
A periodic pattern with hexagonal holes made out of the einstein monotiles
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Dirk Lorenz @dirque.bsky.social · 28/12/2025
And another one!
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Randall Munroe @xkcd.com · 26/12/2025
Funny Numbers xkcd.com/3184/
Comic. [Banner: Mathematical Society: 2025 Meeting.] PERSON 1 with bun: Any other new developments from the year to cover before we wrap? PERSON 2: Oh, the teens picked a new funny number. PERSON 3 with short hair: Aww, I’m glad to hear they’re still doing that. PERSON 4 with ponytail: I’ll add it to the list. [List: 23 (skidoo!; 42; 69; 420; 1,337; 58,008; [circled]: 67]
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Dirk Lorenz @dirque.bsky.social · 27/12/2025
New periodic pattern from aperiodic tiles dropped: 🧮 #mathsky
A periodic pattern out of Einstein monotiles (with hexagonal holes)
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Peter Keep @mathprofpeter.bsky.social · 16/12/2025
Does anyone have a links to good writing on what "trivial" means in mathematics? How we might define that type of thing? I get why people don't like the term, I want to help students seek out trivial examples/results as a way of getting familiar with whatever property we're working with. #MathSky
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Jonny @jchirinosrguez.bsky.social · 20/11/2025
New paper out! Together with my postdoc advisors @esoubies.bsky.social and Cédric Févotte :) We study the optimization landscape of L0-Bregman relaxations, which naturally arise when one optimizes non-quadratic fidelity terms coupled with the L0-norm. 1/n
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Dirk Lorenz @dirque.bsky.social · 15/10/2025
New on arXiv: Why noise matters in learned regularization! Data-driven regularizers fail without noise structure. 🎯 Tikhonov, Lavrentiev, quadratic — not equal under non-white noise. 🤫 Spoiler: Optimal reconstruction needs proper noise modeling. 👉 Regularizer choice = structure and noise.
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Petra Schwer @petraschwer.bsky.social · 19/09/2025
What does it mean to do mathematics? Read my personal answer here: web.mathi.uni-heidelberg.de/content/uplo... #mathsky #math #question
web.mathi.uni-heidelberg.de
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Dirk Lorenz @dirque.bsky.social · 11/09/2025
So you agree that the sine function is not decreasing, but you won't say that it's non-decreasing? But alas math has such a precise language! 🧮
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Adrienne Hestenes @ahestenes.bsky.social · 06/09/2025
Ta daaa! I give you the Lorentz Attractor thanks to the free pattern from #ThreadedTheorems and also @samjshah.bsky.social whose posted work I admired. #StemBroidery #MathArt #MathSky
An embroidery in a circular hoop of the Lorentz Strange Attractor.  Embroidered using backstitch and variegated thread of colors aqua, indigo, and pink.  The pattern loops around giving a two lobed appearance of a butterfly.
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siagdata.bsky.social @siagdata.bsky.social · 11/08/2025
Join us for a panel on “Careers in Mathematics of Data Science” tomorrow morning!
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siagdata.bsky.social @siagdata.bsky.social · 15/08/2025
Our latest WebMDS webinar was a blast! Check out our panel discussion of "Careers in Mathematics of Data Science" on youtube: youtu.be/qdlJJLT4ddQ?...
youtu.be
Panel: Careers in Mathematics of Data Science
YouTube video by Society for Industrial and Applied Mathematics (SIAM)
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siagdata.bsky.social @siagdata.bsky.social · 01/08/2025
Register at siam.zoom.us/webinar/regi...
siam.zoom.us
Welcome! You are invited to join a webinar: Webinar on the Mathematics of Data Science. After registering, you will receive a confirmation email about joining the webinar.
Panel: Careers in Mathematics of Data Science Join us for an engaging panel discussion on careers in the mathematics of data science, featuring experts from academia, industry, and national labs. Thi...
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siagdata.bsky.social @siagdata.bsky.social · 01/08/2025
Save the Date! The SIAM Activity Group on Data Science (SIAG/DATA) invites you to join us for a panel on the topic: Careers in Mathematics of Data Science Tuesday, August 12, 2025 | 9:00 AM PT | Zoom Webinar Panelists: Marta D’Elia, Elizabeth Newman, David Uminsky
siam.zoom.us
Welcome! You are invited to join a webinar: Webinar on the Mathematics of Data Science. After registering, you will receive a confirmation email about joining the webinar.
Panel: Careers in Mathematics of Data Science Join us for an engaging panel discussion on careers in the mathematics of data science, featuring experts from academia, industry, and national labs. Thi...
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Ben Grimmer @profgrimmer.bsky.social · 05/08/2025
I've invented a simple, lovely math puzzle I expect every AI fails: Suppose you're a mathematical sailor at sea on a boat that has a perfectly cylindrical hole in the floor. All you brought is a collection of every p norm ball except p=2 (drat!). What do you do to cork the hole and save yourself?
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Dirk Lorenz @dirque.bsky.social · 07/07/2025
A: A mathematical statement/concept makes intuitive sense. B: There is a sound framework where a mathematical statement/concept can be proven/defined. I tend to believe that A ⇒ B, but not vice versa. (Thinking about Dirac's delta and the Banach-Tarski paradox, for example.) #🧮
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Dirk Lorenz @dirque.bsky.social · 25/06/2025
I still did not subscribe to d(Amazon)/dx…
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Eigenraum @eigenraum.bsky.social · 19/06/2025
Die Frage P=NP? ist eines der Milleniumsprobleme und somit lohnenswertes Ziel für Hobby- und Profimathematiker:innen. www.claymath.org/millennium/p... 🧵
claymath.org
P vs NP - Clay Mathematics Institute
If it is easy to check that a solution to a problem is correct, is it also easy to solve the problem? This is the essence of the P vs NP question. Typical of the NP problems is that of the Hamiltonian...
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Dirk Lorenz @dirque.bsky.social · 19/06/2025
I sample points uniformly on the sphere and then look at them on a map (in longitude and z-coordinate). STILL UNIFORMLY DISTRIBUTED! 🤯 (Quite a nice fact that is special to three dimensions: Each coordinate of a random vector uniformly on the uni sphere is uniform in [-1,1].) #🧮
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Dirk Lorenz @dirque.bsky.social · 13/06/2025
The recording of the @siagdata.bsky.social webinar "Teaching the mathematics of data science" is online! youtu.be/nynELwnA8ow?...
youtu.be
Teaching the Mathematics of Data Science | Expert Panel Discussion
YouTube video by Society for Industrial and Applied Mathematics (SIAM)
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siagdata.bsky.social @siagdata.bsky.social · 28/05/2025
On Parameterizing Optimal Transport with Elastic Costs with Marco Cuturi youtu.be/tltdW8L68PI
youtu.be
On Parameterizing Optimal Transport with Elastic Costs with Marco Cuturi
YouTube video by Society for Industrial and Applied Mathematics (SIAM)
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siagdata.bsky.social @siagdata.bsky.social · 28/05/2025
The Data and Science of Elections with Moon Duchin youtu.be/ykk4ddjukoA
youtu.be
The Data and Science of Elections with Moon Duchin
YouTube video by Society for Industrial and Applied Mathematics (SIAM)
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siagdata.bsky.social @siagdata.bsky.social · 28/05/2025
Smartphone Privacy: How to Learn from Distributed, Private Data with Jelani Nelson youtu.be/YduytyEvTQA
youtu.be
Smartphone Privacy: How to Learn from Distributed, Private Data with Jelani Nelson
YouTube video by Society for Industrial and Applied Mathematics (SIAM)
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siagdata.bsky.social @siagdata.bsky.social · 28/05/2025
The Emerging Science of Benchmarks with Moritz Hardt youtu.be/ySXQm7NIVN8
youtu.be
The Emerging Science of Benchmarks with Moritz Hardt
YouTube video by Society for Industrial and Applied Mathematics (SIAM)
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siagdata.bsky.social @siagdata.bsky.social · 28/05/2025
Plenary videos from SIAM MDS 2024 just dropped! Check out these great talks:
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Dirk Lorenz @dirque.bsky.social · 26/05/2025
👇 the logic of capitalism
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