## 142 Reputation

16 years, 242 days

## efficient way to work out exterior produ...

Hello,

http://www.maplesoft.com/support/help/Maple/view.aspx?path=tensor/exterior_prod

and I was wondering : what is the most efficient way to work out basic combinations of bivectors (or trivectors...)

Suppose for instance I have a 4-dimensional space with basis (e1,e2,e3,e4) and I would want to work out

(e_1 -e2+ e3) wedge (e_2-e_4),

how could I do this?

(I just...

## Sorting a list + obtaining sign of permu...

Hello,

I am working with wedge products, and I came up with this question: how can I efficiently sort a list of indices, and obtain the sign of the associated permutation?

So for [4,3] I would like to obtain [3,4]-

for [1,4,2] I would want to obtain [1,2,4] -

for [2,1,4,3] I would want to obtain [1,2,3,4]+

I know I can do sort([4,3]) but what about the sign of that permutation?

Thanks!

## Maple stops when computer is on stand-by...

Maple

Hello,

(sorry if this appeared elsewhere, but it seems my first try to ask this failed)

I tried to use Maple last night to do some heavy computational work, but it turns out (I let him print time()) that he was only active for about an hour.  He did not do anything when my Macbook Pro was on stand-by.

This morning, when he woke up, he was unwilling to stop!  I pushed the "Interrupt the current operation" button...

## Kernel connection lost on very simple Li...

Maple

Hello

I am using Maple 15 on a Macbook Pro, and I was using this simple code

restart;with(LinearAlgebra):
P := Matrix(4, 4,    [[1, s, t, 0], [0, 1, s, 0], [0, 0, 1, s], [0, 0, 0, s]]);
DiagonalMatrix(Column(P, 2)).P;

which should be easy but then Maple gives me a pop-up message:

"Kernel connection has been lost.  The kernel returned the following error message:

## D can be unprotected, but is still seen ...

Maple

Hello,

I always used something different from D when using diagonal matrices. Now I learned I can unprotect D.

However, I got this:

> restart; with(LinearAlgebra);
> unprotect(D);
> D := DiagonalMatrix([2, 3]);
> D.D;D^(2);
Error, invalid 'D' operator

Maple does interpret D as a matrix that he can square, but the exponentional notation can't be used as he sees it as some sort of operator?  Can anyone point out my mistake?

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