Hacker News new | past | comments | ask | show | jobs | submit login

> In fact a student of Lorentz, Fokker, working with Einstein was able to show that Nordstrom's theory was equivalent to an expression involving the ricci scalar and a trace of the stress energy tensor. Unlike Einstein's proposal around this time, it was diffeomorphism invariant.

"I know some of these words."

Ricci scalar: number assigned to each point of a space describing curvature at that point

Stress-energy tensor (field): multidimensional quantity assigned to each point of a space describing how matter and energy are concentrated and moving at that point.

Trace: coordinate invariant transformation that turns a tensor field into a scalar field.

Diffeomorphism invariant: the object in question has the same description regardless of arbitrary coordinate changes

Applications are open for YC Winter 2020

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact