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Recent Posts
- Exterior algebra 2026/01/18
- Kronecker generalized deltas and Levi-Civita epsilons 2026/01/09
- It’s all about permutations 2025/12/28
- Densities 2025/12/21
- Tensors on a picnic 2025/12/14
- Tensors are geometric objects 2025/12/10
- Conformal structure – until the puppy grows up 2025/12/07
- Growing Out of the Sandbox 2025/12/02
- Blog reincarnation with analytic idealism 2025/11/30
- Minkowski patches in the Einstein universe 2025/11/27
- Floating in the Einstein Universe 2025/11/24
- Comments on Clifford algebras 2019/01/24
- Comment on “Could ordinary quantum mechanics be just fine for all practical purposes?” by Alexey Nikulov 2018/03/08
- Spinning Top – Space Odity 2017/05/28
- Geodesics of left invariant metrics on matrix Lie groups – Part 2 Conservation laws 2017/05/26
- Geodesics of left invariant metrics on matrix Lie groups – Part 1 2017/05/24
- Killing vectors, geodesics, and Noether’s theorem 2017/05/23
- SL2R as anti de Sitter space cont. 2017/05/15
- Becoming anti de Sitter 2017/05/14
- SL(2,R) Killing vector fields in coordinates 2017/05/11
- Riemannian metrics – left, right and bi-invariant 2017/05/09
- Riemannian metric on SL(2,R)- explicit formula 2017/05/08
- Riemannian metric on SL(2,R) 2017/05/07
- Parametrization of SL(2,R) 2017/05/06
- Curvature of the upper half-plane 2017/05/05
- Geodesics on upper half-plane factory direct 2017/05/04
- Einstein the Stubborn 2017/05/03
- Dedekind tessellation on the Poincaré disk 2017/05/02
- Dedekind tessellation or circles all the way down 2017/04/30
- Real magic – space-time in Lie algebra 2017/04/29
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- Anna on Exterior algebra
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Monthly Archives: December 2025
It’s all about permutations
Permutations appear whenever “things are the same, but in a different order.” That simple idea hides a powerful engine that underlies physics, geometry, information, and even the notion of identity itself. In quantum mechanics, identical particles do not carry little … Continue reading
Densities
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
Tensors on a picnic
This series of posts is meant as a “gentle introduction to …”. It’s so gentle that some readers may even find it boring. They might say, “All this is well known—get to the point!” But I can’t think of another … Continue reading
