Writings

Writings

  • My undergraduate thesis, advised by Barry Mazur, was on doing local class field theory explicitly. The ultimate goal was to give an explanation of why the cohomological approach and the formal group approach should agree, but I didn’t succeed. So the thesis became two separate parts put together.
  • I wrote an introductory linear algebra book, A rough guide to linear algebra, which is freely available from the link. For short introduction to the book, read this post.
  • During 2019–2020, I went over Chapters II and III of Hartshorne’s Algebraic Geometry and tried solving all the exercises. The result can be accessed through this post.

Papers

Here are my papers, in reverse chronological order.

  1. Peter Horak and Dongryul Kim, Connected cubic graphs with the maximum number of perfect matchings, submitted (2020), arXiv:2006.13459.
  2. Peter Horak and Dongryul Kim, 50 years of the Golomb–Welch conjecture, IEEE Trans. Inform. Theory 64 (2018), no. 4, part 2, 3048–3061. MR 3784608, arXiv:1706.03589.
  3. Dongryul Kim, Nonexistence of perfect 2-error-correcting Lee codes in certain dimensions, European J. Combin. 63 (2017), 1–5. MR 3645781, arXiv:1701.08412.

Olympiad stuff

The following are all notes dating back from my high school/early college days. Unfortunately, a lot of them are in Korean.

  • p-adic numbers
  • Roots of unity
  • In the year 2014 and 2015, I tried to run a weekly problem contest in my high school. Here is the problem collection: POW-compressed.
  • There are a few short notes I wrote for instructional purposes.
  • These are a set of unreasonably difficult mock exams I used for the 2017 IMO training: 2017 mock IMO. For perspective, the average score for the Korean team on the first exam was 11 out of 28.
  • The following are math problems from KöMaL, a math and physics journal for high school students in Hungary. Their math problems used to have a ‘N’ category, which had a lot of difficult and interesting problems. Here is the compilation of the problems together with my addition of hints: KöMaL problems.

Notes

I usually I type notes whenever I attend a lecture. This practice is called live-TeXing, and I have become quite skilled at it.

  • During my undergraduate years at Harvard, I tried to take as many courses as possible and collected the notes on a github repository. These notes are of pretty poor quality, since with I was lost with high probability when I wrote them.
  • In July 2017, Joel Spencer taught at a summer school on probabilistic methods. The notes are available here.