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arXiv:1205.5935math-ph

Geometric Algebra

Eric Chisolm

Abstract

This is an introduction to geometric algebra, an alternative to traditional vector algebra that expands on it in two ways: 1. In addition to scalars and vectors, it defines new objects representing subspaces of any dimension. 2. It defines a product that's strongly motivated by geometry and can be taken between any two objects. For example, the product of two vectors taken in a certain way represents their common plane. This system was invented by William Clifford and is more commonly known as Clifford algebra. It's actually older than the vector algebra that we use today (due to Gibbs) and includes it as a subset. Over the years, various parts of Clifford algebra have been reinvented independently by many people who found they needed it, often not realizing that all those parts belonged in one system. This suggests that Clifford had the right idea, and that geometric algebra, not the reduced version we use today, deserves to be the standard "vector algebra." My goal in these notes is to describe geometric algebra from that standpoint and illustrate its usefulness. The notes are work in progress; I'll keep adding new topics as I learn them myself.

arXiv comments
92 pages and 1 figure
Journal reference
DOI
Subjects
math-phMathematical Physics

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Linked by 6 identifiable commenters in 13 comments across 11 threads, from Jul 2016 to Aug 2024. Found in 1 HN submission from Nov 2020 to Nov 2020. Open submission discussions.

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Discussed in comments11 threads

    • thank you very much for the context! wrt ewd1300, https://www.cs.utexas.edu/~EWD/ewd13xx/EWD1300.PDF is a scan in the original handwriting. it's been a number of years since i read it, and i'd forgotten most of its contents, though evidently i've incorporated some of them…

      kragenView on HNParent context

    • I second this thinking. You may be interested in reading about Geometric Algebra[1] and Infinitesimal Calculus[2], as two other alternative frameworks for the symbolic tooling used in the physical sciences. Together with symbolic manipulation and calculation software, I also…

      QemView on HNParent context

    • The author went to MIT, worked for NASA, and now lives in San Francisco https://twitter.com/mferraro89 It is unexceptional (indeed, expected) to get through an American undergraduate science or engineering degree without ever taking an abstract algebra course (much less the 2+…

      jacobolusView on HNParent context

    • > I've yet to see [...] Most implementations I have seen do much more than quaternions. How hard did you look? Here’s an example you can play with in a browser, https://enkimute.github.io/ganja.js/ But what is implemented in computers is not 1:1 with the algebraic tools that can…

      jacobolusView on HNParent context

    • For anyone looking for a sane way to study this stuff, what finally made sense to me was (1) study discrete differential geometry from Keenan Crane's notes: https://www.cs.cmu.edu/~kmcrane/Projects/DDG/ ; (2) Read these notes on geometric algebra that formally lay down what the…

      bolluView on HNParent context

  1. Geometric Algebra for Python 1 comment
    • It’s kind of the same, actually. You can treat the individual entries as “components” in a 2^d-vector with special multiplicative structure, which essentially transforms in specific ways. These axioms of GA lay that out more clearly: https://arxiv.org/pdf/1205.5935.pdf…

      LolWolfView on HNParent context

    • What is your background/perspective? For introductory motivation, check out https://www.shapeoperator.com/2016/12/12/sunset-geometry/ And perhaps follow up with the GA for Computer Science book, or if you like (or want to learn about) Newtonian mechanics, try Hestenes’s book New…

      jacobolusView on HNParent context

    • You might enjoy https://arxiv.org/abs/1205.5935

      jacobolusView on HNParent context

    • Geometric algebra has a definition that is more specific than any use of geometry to teach Elementary Algebra on real numbers. https://en.m.wikipedia.org/wiki/Geometric_algebra https://en.m.wikipedia.org/wiki/Clifford_algebra For teaching geometric algebra, there are curricula…

      dahartView on HNParent context

    • Here’s a comment I made elsewhere recently: * * * You might start with teasers like Hestenes’s papers [“Reforming the Mathematical Language of Physics”][oersted], [“Grassmann’s Vision”][gvision], etc. For a summary from a mathy perspective, try Chisolm’s [book-like thingy on…

      jacobolusView on HNParent context

    • Here, start with these: (1) http://geocalc.clas.asu.edu/pdf/OerstedMedalLecture.pdf (2) http://geocalc.clas.asu.edu/pdf/GrassmannsVision.pdf (3) http://geometry.mrao.cam.ac.uk/wp-content/uploads/2015/02/Im... (4) https://arxiv.org/pdf/1205.5935v1.pdf (5)…

      jacobolusView on HNParent context

    • You might find this clearer than other sources: http://arxiv.org/abs/1205.5935 Also check out http://geocalc.clas.asu.edu/pdf/LGasSG.pdf

      jacobolusView on HNParent context

    • Kalid: you should really check out geometric algebra (a.k.a. Clifford algebra). It will give you a much deeper understanding of what i is and what the exponential function is, and how they generalize to higher dimensions and more complicated models, and it will help stitch…

      jacobolusView on HNParent context

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