The equation shown is a type of decomposition of a Lie algebra g that was introduced by Élie Cartan in his doctoral thesis. h is called a Cartan subalgebra of g.

To answer what a Lie algebra is, an extremely hand-wavy description might be: a Lie group is a continuous group of symmetries of some geometric object (for example, the group SO(3) of rotations of three-dimensional space), and the corresponding Lie algebra is the “tangent space” to the group, that is, the space of tiny changes you can make that lie “along” the group.

A lot of things in Lie theory and differential geometry are named after Élie Cartan, or sometimes after his son Henri.

If the head needs to be empty, I find that droney Japanese noise is the best way to get that. Example: Aube - Flare

Lots of great sf/fantasy authors mentioned already, including some I’d argue for as great writers regardless of genre (Ursula K. Le Guin, Gene Wolfe, N. K. Jemisin).

I have three more to suggest in this genre and from this period:

• C. J. Cherryh (Cyteen, Foreigner series, lots more) uses the lens of alien societies – just different enough from ours – to make us look critically at the structure of our own;

• Sheri S. Tepper (Grass, Raising the Stones, The Gate to Women’s Country) carries one or another of the dark currents underlying our culture to its horrifying conclusion, and shows us what we get;

• Lois McMaster Bujold (Vorkosigan saga) gives us a hilarious and improbable hero who utterly transcends his disabilities, in the end perfectly embodying what it seems he could never hope to be.