Address review comments: negative sign and AdjointTranspose section
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doc/math.lyx
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doc/math.lyx
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@ -5086,6 +5086,13 @@ reference "ex:projection"
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\begin_layout Subsection
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\begin_layout Subsection
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Derivative of Adjoint
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Derivative of Adjoint
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\begin_inset CommandInset label
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LatexCommand label
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name "subsec:pose3_adjoint_deriv"
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\end_inset
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\end_layout
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\end_layout
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\begin_layout Standard
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\begin_layout Standard
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@ -5098,7 +5105,7 @@ Consider
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\end_inset
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\end_inset
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.
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.
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The derivative is notated (see
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The derivative is notated (see Section
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\begin_inset CommandInset ref
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\begin_inset CommandInset ref
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LatexCommand ref
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LatexCommand ref
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reference "sec:Derivatives-of-Actions"
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reference "sec:Derivatives-of-Actions"
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@ -5114,7 +5121,7 @@ noprefix "false"
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\begin_layout Standard
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\begin_layout Standard
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\begin_inset Formula
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\begin_inset Formula
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\[
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\[
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Df_{(T,y)}(\xi,\delta y)=D_{1}f_{(T,y)}(\xi)+D_{2}f_{(T,y)}(\delta y)
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Df_{(T,\xi_{b})}(\xi,\delta\xi_{b})=D_{1}f_{(T,\xi_{b})}(\xi)+D_{2}f_{(T,\xi_{b})}(\delta\xi_{b})
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\]
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\]
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\end_inset
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\end_inset
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@ -5149,11 +5156,12 @@ D_{2}f_{(T,\xi_{b})}(\xi_{b})=Ad_{T}
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\end_inset
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\end_inset
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To compute
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We will derive
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\begin_inset Formula $D_{1}f_{(T,\xi_{b})}(\xi_{b})$
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\begin_inset Formula $D_{1}f_{(T,\xi_{b})}(\xi)$
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\end_inset
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\end_inset
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, we'll first define
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using two approaches.
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In the first, we'll define
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\begin_inset Formula $g(T,\xi)\triangleq T\exp\hat{\xi}$
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\begin_inset Formula $g(T,\xi)\triangleq T\exp\hat{\xi}$
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\end_inset
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\end_inset
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@ -5194,18 +5202,30 @@ Now we can use the definition of the Adjoint representation
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\begin_layout Standard
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\begin_layout Standard
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\begin_inset Formula
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\begin_inset Formula
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\begin{align*}
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\begin{align*}
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D_{1}f_{(T,\xi_{b})}(\xi)=D_{1}\left(Ad_{T\exp(\hat{\xi})}\hat{\xi}_{b}\right)(\xi) & =D_{1}\left(g\hat{\xi}g^{-1}\right)(\xi)\\
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D_{1}f_{(T,\xi_{b})}(\xi)=D_{1}\left(Ad_{T\exp(\hat{\xi})}\hat{\xi}_{b}\right)(\xi) & =D_{1}\left(g\hat{\xi}_{b}g^{-1}\right)(\xi)\\
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& =\left(D_{2}g_{(T,\xi)}(\xi)\right)\hat{\xi}g^{-1}(T,0)+g(T,0)\hat{\xi}\left(D_{2}g_{(T,\xi)}^{-1}(\xi)\right)\\
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& =\left(D_{2}g_{(T,\xi)}(\xi)\right)\hat{\xi}_{b}g^{-1}(T,0)+g(T,0)\hat{\xi}_{b}\left(D_{2}g_{(T,\xi)}^{-1}(\xi)\right)\\
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& =T\hat{\xi}\hat{\xi}_{b}T^{-1}-T\hat{\xi}_{b}\hat{\xi}T^{-1}\\
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& =T\hat{\xi}\hat{\xi}_{b}T^{-1}-T\hat{\xi}_{b}\hat{\xi}T^{-1}\\
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& =T\left(\hat{\xi}\hat{\xi}_{b}-\hat{\xi}_{b}\hat{\xi}\right)T^{-1}\\
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& =T\left(\hat{\xi}\hat{\xi}_{b}-\hat{\xi}_{b}\hat{\xi}\right)T^{-1}\\
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& =-Ad_{T}(ad_{\xi_{b}}\hat{\xi})\\
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& =Ad_{T}(ad_{\hat{\xi}}\hat{\xi}_{b})\\
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& =-Ad_{T}(ad_{\hat{\xi}_{b}}\hat{\xi})\\
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D_{1}F_{(T,\xi_{b})} & =-(Ad_{T})(ad_{\hat{\xi}_{b}})
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D_{1}F_{(T,\xi_{b})} & =-(Ad_{T})(ad_{\hat{\xi}_{b}})
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\end{align*}
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\end{align*}
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\end_inset
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\end_inset
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An alternative, perhaps more intuitive way of deriving this would be to
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Where
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use the fact that the derivative at the origin
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\begin_inset Formula $ad_{\hat{\xi}}:\mathfrak{g}\rightarrow\mathfrak{g}$
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\end_inset
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is the adjoint map of the lie algebra.
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\end_layout
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\begin_layout Standard
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The second, perhaps more intuitive way of deriving
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\begin_inset Formula $D_{1}f_{(T,\xi_{b})}(\xi_{b})$
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\end_inset
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, would be to use the fact that the derivative at the origin
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\begin_inset Formula $D_{1}Ad_{I}\hat{\xi}_{b}=ad_{\hat{\xi}_{b}}$
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\begin_inset Formula $D_{1}Ad_{I}\hat{\xi}_{b}=ad_{\hat{\xi}_{b}}$
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\end_inset
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\end_inset
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@ -5224,28 +5244,212 @@ An alternative, perhaps more intuitive way of deriving this would be to
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\begin_layout Standard
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\begin_layout Standard
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\begin_inset Formula
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\begin_inset Formula
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\[
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\[
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D_{1}Ad_{T}\hat{\xi}_{b}(\xi)=D_{1}Ad_{T*I}\hat{\xi}_{b}(\xi)=Ad_{T}\left(D_{1}Ad_{I}\hat{\xi}_{b}(\xi)\right)=Ad_{T}\left(ad_{\hat{\xi}_{b}}(\xi)\right)
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D_{1}Ad_{T}\hat{\xi}_{b}(\xi)=D_{1}Ad_{T*I}\hat{\xi}_{b}(\xi)=Ad_{T}\left(D_{1}Ad_{I}\hat{\xi}_{b}(\xi)\right)=Ad_{T}\left(ad_{\hat{\xi}}(\hat{\xi}_{b})\right)=-Ad_{T}\left(ad_{\hat{\xi}_{b}}(\hat{\xi})\right)
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\]
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\]
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\end_inset
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\end_inset
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It's difficult to apply a similar procedure to compute the derivative of
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\end_layout
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\begin_inset Formula $Ad_{T}^{T}\hat{\xi}_{b}^{*}$
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\begin_layout Subsection
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Derivative of AdjointTranspose
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\end_layout
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\begin_layout Standard
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The transpose of the Adjoint,
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\begin_inset Formula $Ad_{T}^{T}:\mathfrak{g^{*}\rightarrow g^{*}}$
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\end_inset
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\end_inset
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(note the
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, is useful as a way to change the reference frame of vectors in the dual
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space
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(note the
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\begin_inset Formula $^{*}$
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\begin_inset Formula $^{*}$
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\end_inset
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denoting that we are now in the dual space) because
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denoting that we are now in the dual space)
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.
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To be more concrete, where
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as
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\begin_inset Formula $Ad_{T}\hat{\xi}_{b}$
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\end_inset
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converts the
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\emph on
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twist
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\begin_inset Formula $\xi_{b}$
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from the
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\begin_inset Formula $T$
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\end_inset
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frame,
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\begin_inset Formula $Ad_{T}^{T}\hat{\xi}_{b}^{*}$
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\end_inset
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converts the
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wrench
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\begin_inset Formula $\xi_{b}^{*}$
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\end_inset
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from the
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\begin_inset Formula $T$
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\end_inset
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frame
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.
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It's difficult to apply a similar derivation as in Section
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "subsec:pose3_adjoint_deriv"
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plural "false"
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caps "false"
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noprefix "false"
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\end_inset
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for the derivative of
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\begin_inset Formula $Ad_{T}^{T}\hat{\xi}_{b}^{*}$
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\end_inset
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because
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\begin_inset Formula $Ad_{T}^{T}$
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\begin_inset Formula $Ad_{T}^{T}$
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\end_inset
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\end_inset
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cannot be naturally defined as a conjugation so we resort to crunching
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cannot be naturally defined as a conjugation, so we resort to crunching
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through the algebra.
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through the algebra.
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The details are omitted but the result is a form vaguely resembling (but
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The details are omitted but the result is a form that vaguely resembles
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not quite) the
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(but does not exactly match)
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\begin_inset Formula $ad(Ad_{T}^{T}\hat{\xi}_{b}^{*})$
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\begin_inset Formula $ad(Ad_{T}^{T}\hat{\xi}_{b}^{*})$
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\end_inset
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\end_inset
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