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  • Category: Mathematics
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Finding the compliment   Message List  
Reply Message #7854 of 20696 |
Finding the wedge product?

So Gene, you've given us a nice description of how to compute the
complement for arbitrary dimension and grade. Now how about the wedge
product between pairs of multivectors of arbitrary dimension (and
possibly different) grades? Graham, feel free to chime in here too. :-)






Thu Nov 20, 2003 3:19 am

dkeenanuqnetau
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Message #7854 of 20696 |
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... Thanks very much for these. Please don't be offended by my attempts to translate some parts in a way that I imagine might be more easily comprehended by...
Dave Keenan
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Nov 20, 2003
1:12 am

So Gene, you've given us a nice description of how to compute the complement for arbitrary dimension and grade. Now how about the wedge product between pairs...
Dave Keenan
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Nov 20, 2003
3:19 am

... wedge ... too. :-) I suggest simply using the definition....
Gene Ward Smith
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Nov 20, 2003
8:26 pm

... Certainly, to find the wedge product of two wedgies x an y: Initialize the result to the empty wedgie. Take every distinct basis element of x in turn (by...
Graham Breed
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Nov 20, 2003
9:04 pm

... 1*5=5, you musta meant....
Paul Erlich
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Nov 20, 2003
11:02 pm

That's great Graham. I think I get it now. Let me try feeding it back in a different way so you can tell me if I've got it right, and so others may have...
Dave Keenan
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Nov 22, 2003
12:04 pm

... Thanks Dave. Can someone confirm this? I'm about to take it as Gospel. -C....
Carl Lumma
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Nov 22, 2003
5:01 pm

... back ... It looked good to me....
Gene Ward Smith
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Nov 22, 2003
10:25 pm

... Thanks Gene. I'll bet there were lots of mathematical nits you could have picked, with my presentation, so I really appreciate a simple response like this....
Dave Keenan
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Nov 23, 2003
12:40 am

Oops. Something went missing near the end there. It should have been: Now we sum the products with the same index. product index a1*b23 +...
Dave Keenan
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Nov 22, 2003
10:50 pm

... Can you post the entire corrected thing? -C....
Carl Lumma
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Nov 23, 2003
6:33 am

... i've already done it here: http://sonic-arts.org/dict/wedge-product.htm Gene, can you give me the rigorous mathematical definition as well? -monz...
monz
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Nov 23, 2003
7:26 am

It would be nice to have a shortcut to avoid actually doing all those index position swaps to find the sign of each product of scalars. We already have such a...
Dave Keenan
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Nov 23, 2003
2:16 am

I think I've found one shortcut. But there may yet be a simpler one. Given that the indexes of the two coefficients are respectively I = {i1 i2 i3 ...} and J =...
Dave Keenan
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Nov 23, 2003
4:16 am

The more I think about it the less I think that index permutation parity algorithm will work in general. Here's one that does ...
Dave Keenan
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Nov 23, 2003
6:10 am

... I think that's equivalent to the one I'm using, which I got from a group theory book. (Actually, the book gave a slightly different algorithm, presumably...
Graham Breed
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Nov 23, 2003
8:55 am

... Right, but if you use a fixed-length bitset implementation of the compound indices (e.g. 32 bits) then there's no requirement for sorting. You just OR them...
Dave Keenan
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Nov 24, 2003
1:38 am

... You mean I shouldn't take your thing as Gospel just yet? ... http://tinyurl.com/wiz6 So, can we get a version of your Gospel with this rolled in? -Carl...
Carl Lumma
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Nov 25, 2003
7:49 pm

... Lets first take the simplest case worth considering. The wedge product of two 3-limit (2D) vectors. [a1 a2> ^ [b1 b2> The procedure is to first list every...
Dave Keenan
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Nov 26, 2003
9:29 am

... "Lexigraphic order", no? More later; I can't think in this hick country! (Montana) -Carl...
Carl Lumma
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Nov 26, 2003
11:53 pm

... Yes. Although I think it's "lexicographic"....
Dave Keenan
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Nov 27, 2003
1:37 am

... Product of the differences might do....
Gene Ward Smith
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Nov 23, 2003
7:26 am

... Are you sure? Do you have an example? Graham...
Graham Breed
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Nov 20, 2003
9:05 pm

... Yes. Disturbing isn't it? It occurs only for all odd grades in all even dimensions (where the dimension is the index of the limiting prime). So the...
Dave Keenan
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Nov 20, 2003
10:36 pm

... always ... it occurs in odd dimensions too. ... The ... be ... ocurrence ... you missed 5-limit scalars and pseudoscalars (3D grades 0 and 3)....
Paul Erlich
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Nov 20, 2003
11:10 pm

... I don't think so. See page 10 of http://www.ses.swin.edu.au/homes/browne/grassmannalgebra/book/bookpdf/TheComplement.pdf...
Dave Keenan
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Nov 20, 2003
11:46 pm

... http://www.ses.swin.edu.au/homes/browne/grassmannalgebra/book/bookpdf/ TheComplement.pdf Then the dual must not be the same thing as the Euclidean...
Paul Erlich
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Nov 21, 2003
10:58 pm

... complement. What dual are we talking about?...
Gene Ward Smith
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Nov 21, 2003
11:13 pm

... I was getting my information from the GABLE program and from this tutorial: http://carol.science.uva.nl/~leo/GABLE/tutorial.pdf see page 18....
Paul Erlich
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Nov 21, 2003
11:44 pm

... complement ... it's the ... analogous to ... always ... that's easy -- in 3-dimensional space, the dual of e1^e2^e3 is 1, while the dual of 1 is -e1^e2^e3....
Paul Erlich
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Nov 20, 2003
11:05 pm
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