Category Archives: Spin and rotations

Densities

Posted on 2025/12/21 by arkajad

This post introduces “densities”. There is a very nice book, available on arxiv, by Sean M. Carroll: “Lecture Notes on General Relativity“. There, on p. 52, Carroll writes “… we don’t like tensor densities, we like tensors.” Well, I do … Continue reading →

Posted in AI, Geometry, Lorentz transforations, Spin and rotations, Uncategorized | Tagged , , , , , , | 56 Comments

The mysterious paths on the three-sphere

Posted on 2017/03/12 by arkajad

Wherever you are, whatever you do, there is a certain special direction that takes you out of the infinite labyrinth, and leads to the reincarnation cycle getting closer and closer to the ideal path. Ordinary people do not know about … Continue reading →

Posted in Attitude matrix, Dzhanibekov effect, Moments of inertia, Quaternions, Spin and rotations, Stereographic projection | 2 Comments

When China Rules the World

Posted on 2017/02/27 by arkajad

The title of the post can be found on Wikipedia with additional information. But this post is more personal. Indeed China rulez! Few weeks ago I received the following email: Quantum World-2017 Time: 16th-18th October, 2017 Place: Changsha, Hunan Province, … Continue reading →

Posted in General, Lorentz transforations, Special relativity, Spin and rotations, Spin matrices | 1 Comment