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How can we manipulate and operate with dual quaternionic variables in Mathematica? Since a dual quaternion can be expressed like this

$\hat q = a + \epsilon b $

where $a,b \in \mathbb{H}$, or writing in the explicit form

$\hat q = a_0+a_1 i + a_2 j + a_3 k + \epsilon (b_0+b_1 i + b_2 j + b_3 k ) $

It's possible to utilize the Quaternion package with the definition of dual unit, with $\epsilon^2=0$

\[\Epsilon] /: Power[\[Epsilon], n_] := 0 /; n >= 2

to acomplish this?

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    $\begingroup$ You can always express the dual quaternion product as a $8\times8$ matrix product. $\endgroup$
    – yarchik
    Commented Jun 12, 2020 at 21:29

2 Answers 2

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Add this line to your code:

Post=(#/.ε->0)+ε(D[#, ε]/.ε->0)&

Then use quaternions and $ε$.

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  • $\begingroup$ Reference to the other answers implementing dual numbers here $\endgroup$ Commented Oct 31, 2022 at 16:24
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While the answer from Anixx is good for dual number and some basic operations from Quaternions package, you may need to implement the Norm[] and Normalize[] if you want to work with unit dual quaternion. The block code below is my implementation for both functions (developed from Anixx answer and ashen answer in here):

Needs["Quaternions`"]
DQ={(#/.de->0)+de(D[#, de]/.de->0)}&;
a = DQ[Quaternion[0.1,0.2,0.3,0.4]+de Quaternion[0.5,0.6,0.7,0.8]]
MyNorm= Norm[#] /. de -> 0 &;
InternalDotDQ=(List @@(# /. de->0)[[1]]).(List @@ Coefficient[#,de][[1]]) &;
MyNormalize=(# /. de->0)/ MyNorm[#] + de (Coefficient[#,de] / MyNorm[#]  - (# /. de->0) * ((List @@  (# /. de->0)[[1]]).(List @@ Coefficient[#,de][[1]]))/ (MyNorm[#] ^3))&;
b = MyNormalize[a]
InternalDotDQ[b]
MyNorm[b]

Note that unit dual quaternion require the internal dot product = 0 and the new norm = 1, List @@ is Apply List (I need this to perform dot product), (# /. de->0)[[1]] will return the real part, and Coefficient[#,de][[1]] returns the dual part.

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