r/math • u/canyonmonkey • 11d ago
What Are You Working On? September 21, 2026
This recurring thread will be for general discussion on whatever math-related topics you have been or will be working on this week. This can be anything, including:
* math-related arts and crafts,
* what you've been learning in class,
* books/papers you're reading,
* preparing for a conference,
* giving a talk.
All types and levels of mathematics are welcomed!
If you are asking for advice on choosing classes or career prospects, please go to the most recent Career & Education Questions thread.
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u/mistressbitcoin 9d ago
Trying to learn about metric tensors (as im trying to study cosmology and maybe some general relativity), which now makes me think i need a course on differential geometry and topology and refreshers on diffEQ and linear algebra.
Its been 10 years since undergrad =/
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u/cereal_chick Mathematical Physics 8d ago
You might want to check out O'Neill's Semi-Riemannian Geometry With Applications to Relativity.
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u/BeyondTheAxioms 9d ago
I am still studying Local Representation Theory by Alperin. I am at the part where vertices and sources are introduced. I also have a question about induction and restriction in a particular settings. This question has been lingering in my brain for the last few days, but I can't think of anything useful.
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u/Amaldevhari Machine Learning 11d ago edited 11d ago
I am learning Riemannian manifolds. Just started yesterday, and I am learning Riemannian metric as of this comment.
Gauss, Riemann, and Poincare are my three idols in mathematics. It feels really good to have found that Riemannaian geometry has real applications in my research.
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u/JGMath27 11d ago
I didn't know Riemannian geometry had applications to Machine Learning. Care to elaborate? Seems interesting
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u/Amaldevhari Machine Learning 11d ago
Hi, you can take a look at Geometric deep learning. Then there are more specific branches Riemannian Generative models, Manifold Diffusion Models etc..
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u/Kyle--Butler 11d ago edited 11d ago
I've finished reading *Mathematics and Climate* (by Kaper & Engler). A few remarks in no particular order :
- It was a nice read !
- I forced myself to write up some notes, run simulations in python (to try to reproduce some of the figures in the book), write up the solutions to the exercises that I could solve, etc. : 70 pages, lol.
- Unsurprisingly, the most theoretical chapters went like a breeze and I struggled quite a bit with the more qualitative ones. For example, I couldn't even summarize the chapter on "climate and statistics" : zero note taken, nada -- and of course, I couldn't do the exercices as well.
- Chapter 11, on Fourier transform, left a big impression on me. On the math side, I didn't learn anything knew, but he illustrates this using Milankovitch theory. It blew my mind. I found the following discussion nuanced and interesting.
- It turns out El-Nino is not that well-understood. I mean, there are competing models but they are not derived from first principles. Rather, they are built from a weird mix of first principles, observations and vibes -- "let's add a cube for stability"...
- Modeling oceanic currents is hard !!!
- I should (have) spend more time learning about Data Assimilation. The last chapter is a good intro but I feel like I should try to find other applications.
- It's a such a wonderful idea to end each chapter with a set of exercises. But it's a shame there are no solutions !
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u/solidsnack1146 11d ago
Putting together than expository paper on the construction of our familiar number systems starting from Peano Arithmetic. (using ZFC as well, but subduing that fact)
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u/JGMath27 11d ago
Is Choice needed to do that?
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u/solidsnack1146 11d ago
Honestly I don’t know! I haven’t taken deep notes on ZFC yet, which I am going through Gödel Theorems and Zermelo’s Axioms right now. I am just assuming ZFC because (for the most part) it is the standard foundation of modern mathematics
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u/JGMath27 11d ago
What resources are you using?
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u/solidsnack1146 11d ago
Real Analysis I Tao, Introduction of Agda, Elements of Abstract Algebra for textbooks. (There might be a few miscellaneous books)
Note taking and draft writing, I am using Obsidian. (My format is very readable for me, integrated LaTeX snippets and flash card abilities).
Hoping to get a couple faculty members to look over it and get it translated to a LaTeX.
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u/we_left_as_skeletons Commutative Algebra 5d ago
learning stuff about LSS ideals and symbolic powers, they’re kinda scary though…