Ciro Santilli @cirosantilli 40

4 squares are sufficient by Lagrange's four-square theorem.

3 is not enough by Legendre's three-square theorem.

The subsets reachable with 2 and 3 squares are fully characterized by Legendre's three-square theorem.

The default feathers-chat app runs on NeDB (local filesystem JSON database).

Ciro Santilli managed to port it to Sequelize for PostgreSQL as shown at: github.com/cirosantilli/feathers-chat/tree/sequelize-pg

Complexity: NP-intermediate as of 2020:

The basis of RSA: RSA. But not proved NP-complete, which leads to:

archive.org/details/quantumstoryhist0000bagg on the Internet Archive Open Library.

The problem with a single-level paging scheme is that it would take up too much RAM: 4G / 4K = 1M entries per process.

If each entry is 4 bytes long, that would make 4M per process, which is too much even for a desktop computer: ps -A | wc -l says that I am running 244 processes right now, so that would take around 1GB of my RAM!

For this reason, x86 developers decided to use a multi-level scheme that reduces RAM usage.

The downside of this system is that is has a slightly higher access time, as we need to access RAM more times for each translation.

The first really good quantum mechanics theory made compatible with special relativity was the Dirac equation.

And then came quantum electrodynamics to improve it: Dirac equation vs quantum electrodynamics.

TODO: does it use full blown QED, or just something intermediate?

www.youtube.com/watch?v=NtnsHtYYKf0 "Mercury and Relativity - Periodic Table of Videos" by Periodic Videos (2013). Doesn't give the key juicy details/intuition. Also mentioned on Wikipedia: en.wikipedia.org/wiki/Relativistic_quantum_chemistry#Mercury