\(\newcommand{\vf}[1]{\mathbf{\vec{#1}}} \renewcommand{\Hat}[1]{\mathbf{\hat{#1}}} \renewcommand{\bar}{\overline} \newcommand{\Partial}[2]{{\partial#1\over\partial#2}} \newcommand{\PARTIAL}[2]{{\partial^2#1\over\partial#2^2}} \newcommand{\tr}{{\rm tr\,}} \renewcommand{\AA}{\vf A} \newcommand{\BB}{\vf B} \newcommand{\EE}{\vf E} \newcommand{\FF}{\vf F} \newcommand{\GG}{\vf G} \newcommand{\HH}{\vf H} \newcommand{\II}{\vf I} \newcommand{\KK}{\vf K} \renewcommand{\aa}{\vf a} \newcommand{\bb}{\vf b} \newcommand{\ee}{\vf e} \newcommand{\gv}{\vf g} \newcommand{\rr}{\vf r} \newcommand{\uu}{\vf u} \newcommand{\vv}{\vf v} \newcommand{\ww}{\vf w} \newcommand{\grad}{\vf{\boldsymbol\nabla}} \newcommand{\zero}{\vf 0} \newcommand{\ii}{\Hat{\boldsymbol\imath}} \newcommand{\jj}{\Hat{\boldsymbol\jmath}} \newcommand{\kk}{\Hat k} \newcommand{\nn}{\Hat n} \newcommand{\TT}{\Hat T} \newcommand{\rhat}{\Hat r} \newcommand{\xhat}{\Hat x} \newcommand{\yhat}{\Hat y} \newcommand{\zhat}{\Hat z} \newcommand{\that}{\Hat{\boldsymbol\theta}} \newcommand{\phat}{\Hat{\boldsymbol\phi}} \newcommand{\LL}{\mathcal{L}} \newcommand{\DD}[1]{D_{\hbox{\small$#1$}}} \newcommand{\bra}[1]{\langle#1|} \newcommand{\ket}[1]{|#1/rangle} \newcommand{\braket}[2]{\langle#1|#2\rangle} \newcommand{\lt}{<} \newcommand{\gt}{>} \newcommand{\amp}{&} \)