Ciro Santilli @cirosantilli  40

Once again, relies on superconductivity to reach insane magnetic fields. Superconductivity is just so important.

Ciro Santilli saw a good presentation about it once circa 2020, it seems that the main difficulty of the time was turbulence messing things up. They have some nice simulations with cross section pictures e.g. at: www.eurekalert.org/news-releases/937941.

There is a Turing machine that halts for every member of the language with the answer yes, but does not necessarily halt for non-members.

Non-examples: cs.stackexchange.com/questions/52503/non-recursively-enumerable-languages

Subset of recursively enumerable language as explained at: difference between recursive language and recursively enumerable language.

This is the classic result of formal language theory, but there is too much slack between context free and context sensitive, which is PSPACE (larger than NP!).

By Noam Chomsky.

A good summary table that opens up each category much more can be seen e.g. at the bottom of en.wikipedia.org/wiki/Automata_theory under the summary thingy at the bottom entitled "Automata theory: formal languages and formal grammars".

The opposite of from first principles.