About

N. Pinch

Self-taught, somewhere between first-year calculus and three preprints I can't read yet.

N. Pinch is a pen name. I'd rather you remembered the mathematics than me — but the person writing is real, and so are the mistakes.

I'm not a mathematician. I'm someone who read about the Poincaré conjecture, couldn't stop thinking about it, and decided to learn the mathematics properly instead of admiring it from a distance. This site is my notebook, kept in the open: the papers I collect, the books I'm working through, and the things I misunderstood on the way. If you're walking the same road — miles ahead of me or just starting — I'd love to hear from you.

A neckpinch is the moment a Ricci flow squeezes a thin neck down to nothing — the point where Perelman's surgery takes over. It felt like the right name for a notebook about getting stuck and carrying on anyway. See the concept

Write to me — I read everything, and I answer.

What I'm doing

Working through the path, slowly

Most evenings it's a book, a notebook and a cup of something going cold. Rather than keep the same thing up to date in two places, the Path page is the single source of truth: it marks the stages I've finished and the one I'm in now, and every journal entry is filed under the stage it was written in.

Day 93 · 18 journal entries

See where I am Read the journal

Can you help?

What I'm stuck on right now

  1. Why induction needs to be an axiom rather than something you prove. I can use it fine; I can't yet say why it isn't circular. Tell me
  2. Whether I should build the reals by Cauchy sequences (Tao's way) or Dedekind cuts, or whether caring about the difference this early is a waste of time. Tell me

Come along

Ways we could do this together

  • Read with me. Working through the same book? Let's pick a chapter a week and compare notes. Being one chapter ahead of someone is the best reason to actually finish a chapter.
  • Correct me. If an entry here gets something wrong, please say so. I'd much rather be embarrassed today than wrong for another year.
  • Ask an expert. The People page lists Ricci flow specialists and explains how to write to them.
  • Send me things. A paper I should have, a workshop I've missed, a set of notes that helped you — the events list especially is kept by hand and I'd rather not miss anything.
  • Keep your own notebook. If you start one, send me the link. Reading someone else's working-out is the next best thing to having a classmate.