Image taken from craiyon.com, DALL E generated from prompt "newton cradle spectra"
Paper: https://arxiv.org/abs/2206.09927...
...where we talk about nonperturbative behaviour of spectra and eigenvectors under the addition of self-adjoint operators, Cauchy's interlacing theorem, level repulsion, why the gap narrows in adiabatic quantum computing...
It depends on the number of boson and fermion species in the universe.
And it can change depending on the scale you probe!
...that became popular (for a physics paper):
PRL link: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.163603
Pop sci example: https://gizmodo.com/unruh-effect-visible-in-the-lab-physics-1848977467
A paper where we discover acceleration-induced transparency, and describe improving the measurability of the Unruh effect.
The second one is excellent too.
Canadian treasure
And many more important ideas.