SPH: Smoothed-Particle Hydrodynamics

- In this Hydrodynamics, it looks like `i` is a matrix element subscript (and there is no √-1)

- Fedi's is a superhydrodynamic quantum gravity; with Gross-Pitaevski :

From "Light and gravitational waves don't arrive simultaneously" (2023) https://news.ycombinator.com/item?id=38056295 :

> "Gravity as a fluid dynamic phenomenon in a superfluid quantum space. Fluid quantum gravity and relativity." (2015) https://hal.science/hal-01248015/

> In SQS (Superfluid Quantum Space), Quantum gravity has fluid vortices with Gross-Pitaevskii, Bernoulli's, and IIUC so also Navier-Stokes; so Quantum CFD (Computational Fluid Dynamics)