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The Road to Reality Study Notes: Difference between revisions
→5.4 Complex Powers
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=== 5.4 Complex Powers === | === 5.4 Complex Powers === | ||
Returning to the ambiguity problem of multi-valuedness, it seems the best way to avoid issues is when a particular choice of $$logw$$ has been specified. As an example, $$w^z$$ with $$z=1/2$$. We can specify a rotation for $$logw$$ to achieve $$+w^1/2$$, then another rotation of $$logw$$ to achieve $$-w^1/2$$. The sign change is achieved because of the Euler formula <math>e^{π*i}=-1</math>. Note the process: | Returning to the ambiguity problem of multi-valuedness, it seems the best way to avoid issues is when a particular choice of $$logw$$ has been specified. As an example, $$w^z$$ with $$z=1/2$$. We can specify a rotation for $$logw$$ to achieve $$+w^1/2$$, then another rotation of $$logw$$ to achieve $$-w^1/2$$. The sign change is achieved because of the Euler formula <math>e^{π*i}=-1</math>. Note the process: | ||
<math>w^z=e^{zlogw}=e^{zre^{iθ}}=e^{ze^{iθ}}</math>, then specifying rotations for theta allows us to achieve either $$+w^1/2$$ or $$-w^1/2$$. | <math>w^z=e^{zlogw}=e^{zre^{iθ}}=e^{ze^{iθ}}</math>, then specifying rotations for theta allows us to achieve either $$+w^{1/2}$$ or $$-w^{1/2}$$. | ||
Penrose notes an interesting curiosity for the quantity $$i^i$$. We can specify <math>logi=(1/2)πi</math> because of the general relationship <math>logw=logr+iθ</math>. If $$w=i$$, then its easy to see <math>logi=(1/2)πi</math> from noting that y is on the vertical axis in the complex plane (rotation of $$π/2$$). This specification, and all rotations, amazingly achieve real number values for i^i. | Penrose notes an interesting curiosity for the quantity $$i^i$$. We can specify <math>logi=(1/2)πi</math> because of the general relationship <math>logw=logr+iθ</math>. If $$w=i$$, then its easy to see <math>logi=(1/2)πi</math> from noting that y is on the vertical axis in the complex plane (rotation of $$π/2$$). This specification, and all rotations, amazingly achieve real number values for i^i. | ||