ABOUT THIS NOTEBOOK
I'm zzj. This is where I turn mathematical intuition into arguments I can return to, question, and refine.
Why this notebook exists
Mathematics becomes clearer when an idea is written precisely enough to be checked. I use this site to record that process: beginning with a picture or question, following the definitions, and keeping the reasoning that connects them.
These pages are written first as notes to my future self. Publishing them makes the work easier to revisit and leaves a useful trail for anyone studying the same ideas.
How I work
I write the exposition and mathematics in Typst. When an argument benefits from machine-checked certainty, I use Lean 4 to make every assumption and inference explicit.
Formalization is not a replacement for intuition, and intuition is not a replacement for proof. The most useful notes let the two correct each other.
What you'll find
The notebook currently gathers 6 notes under 6 subjects: Real analysis, Topology, Geometry, Lie theory, Mathematical modeling, and Inequalities. Some entries develop a concept from definitions to proofs; others connect mathematical exposition with formal verification or computation.
This is a working notebook rather than a finished textbook. Notes may grow as my understanding changes, while the derivations, references, and source remain visible.
An open notebook
Each note is available for reading on the web, with PDF and Typst editions where applicable. The notes are shared under CC BY-SA 4.0, and their source is public for study, reuse, and correction.