Hermitian operator by Ciro Santilli 37 Updated 2025-07-16
This is the possibly infinite dimensional version of a Hermitian matrix, since linear operators are the possibly infinite dimensional version of matrices.
There's a catch though: now we don't have explicit matrix indices here however in general, the generalized definition is shown at: en.wikipedia.org/w/index.php?title=Hermitian_adjoint&oldid=1032475701#Definition_for_bounded_operators_between_Hilbert_spaces
Originally by Keyhole Inc., which the nbecame Google Maps, but the format seems standardized and has non-Google support, so should be OK.
Busy beaver by Ciro Santilli 37 Updated 2025-07-16
The busy beaver game consists in finding, for a given , the turing machine with states that writes the largest possible number of 1's on a tape initially filled with 0's. In other words, computing the busy beaver function for a given .
There are only finitely many Turing machines with states, so we are certain that there exists such a maximum. Computing the Busy beaver function for a given then comes down to solving the halting problem for every single machine with states.
Some variant definitions define it as the number of time steps taken by the machine instead. Wikipedia talks about their relationship, but no patience right now.
The Busy Beaver problem is cool because it puts the halting problem in a more precise numerical light, e.g.:
They are actually inheritable! But alleles are rare: www.ncbi.nlm.nih.gov/pmc/articles/PMC5559844
Figure 1.
To rats with the same genome differing only in DNA methylation with a different tail phenotype.
Source.
Spectral line by Ciro Santilli 37 Updated 2025-07-16
A single line in the emission spectrum.
So precise, so discrete, which makes no sense in classical mechanics!
Has been the leading motivation of the development of quantum mechanics, all the way from the:

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