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This question is a sequel to Is there a definition of $\log(x)$ for quaternion/octonion $x$? Since $\log(x)$ is multivalued even for complex $x \in \mathbb{C}$, it is impossible to define $\log(x)$ unambiguously in any reasonable way without further information. In the python module https://pypi.org/project/Octonion-Sedenion/, this problem is solved with some kind of short stack. This allows to define $\exp(x)$ and $\log(x)$ in such a way that always $\exp(\log(x)) = x$ and $\log(\exp(x)) = x$ both hold true for $x \in \mathbb{O}$ (octonions) and $x \in \mathbb{S}$ (sedenions). (In the same way it is possible to define these functions for complex $x \in \mathbb{C}$.)

With these definitions now it is possible to define the power function $x^y$ with the property $(x^y)^{1/y} = x$ at least for $x \in \mathbb{S}$ and $y \in \mathbb{O}$. (Since $\mathbb{S}$ is not alternative this no longer holds true for $y \in \mathbb{S}$.)

Question: Is there a reasonable interpretation of $x^y$ if $y \not\in \mathbb{R}_+$? $x^{0.5} = \sqrt{x}$ holds, further we have by specialisation f.i. $(x^{10})^{0.1} = x$. But what is the interpretation of $x^{3+4j}$ for octonions or sedenions $x$?

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It seems that there cannot be a natural interpretation, because there is no canonical definition for the meaning of $x^y$.

There is already no canonical definition when $x$ is a complex number (that is not a positive real) and $y$ is a rational number (that is not an integer), see the accepted answer for this question about quaternions.

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    $\begingroup$ Thank you for the interesting link math.stackexchange.com/questions/703593/… Of course you are right that the same problem arises for complex numbers. But this isn't the point. It's possible to define $\log$ and $\exp$ in such a way that $x^y$ can be defined with some (not all) properties of the real valued $x^y$. Addition breaks this process. $\endgroup$ Commented Jul 5 at 22:06
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    $\begingroup$ @DieterKadelka My claim is that, since the definition of $x^y$ is not canonical, that means there will not be a "reasonable interpretation". If you do not feel my answer is sufficient, could you please indicate what sort of answer you would find sufficient? For example, can you point to what you would call a "reasonable interpretation" of $x^y$ when $x$ and $y$ are merely complex numbers? $\endgroup$
    – Skip
    Commented Jul 6 at 21:46

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