Portal Site and a Small Experiment
The PDF version of this book, errata, revision history, GitHub repository, and links to related notes are collected on the following portal site.
Portal Site
GitHub Pages (English)
https://yokiikoy.github.io/nabla-kaitai/en/ · Japanese edition
This book is available for free. Obvious typo-level corrections are also accepted through GitHub Issues.
Note (on the name)
Incidentally, the term covector space, or Co-Vector Space, is not especially common. In mathematics, it is more usual to say dual space and related terms.
Discord Server
As a small experiment, I have opened a Discord server as a slightly more private place for unorganized ideas and elementary questions that are hard to post on public social media.
The plan is to develop it gradually. At present, it is honestly close to an “empty room.” I hope it can become a place where people interested in science and engineering can gather at a comfortable distance, whether or not the topic is directly related to this book.
If you are interested, please visit the portal site. The invitation link is here.