Cartesian, coordinate
chart coordinates: $x^\tilde{\mu} = \{x, y\}$
chart coordinate basis: $e_\tilde{\mu} = \{e_{\tilde{x}}, e_{\tilde{y}}\}$
embedding coordinates: $u^I = \{x, y\}$
embedding basis $e_I = \{e_{x}, e_{y}\}$
flat metric:
${{{ \eta} _I} _J} = {\overset{I\downarrow J\rightarrow}{\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}}$
transform from basis to coordinate:
${{{ \tilde{e}} _A} ^a} = {\overset{A\downarrow a\rightarrow}{\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}}$
transform from coorinate to basis:
${{{ \tilde{e}} ^a} _A} = {\overset{a\downarrow A\rightarrow}{\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}}$
tensor index associated with coordinate $x$ has operator $e_{x}(\zeta) = $$\frac{\partial \zeta}{\partial x}$
tensor index associated with coordinate $y$ has operator $e_{y}(\zeta) = $$\frac{\partial \zeta}{\partial y}$
chart in embedded coordinates:
${u} = {\overset{I\downarrow}{\left[\begin{matrix} x \\ y\end{matrix}\right]}}$
basis operators applied to chart:
${{{ e} _u} ^I} = {{{ u} ^I} _{,u}}$
${{{ e} _u} ^I} = {\overset{u\downarrow I\rightarrow}{\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}}$
${{{ e} ^u} _I} = {\overset{u\downarrow I\rightarrow}{\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}}$
${{{{{ e} _u} ^I}} {{{{ e} ^v} _I}}} = {\overset{u\downarrow v\rightarrow}{\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}}$
${{{{{ e} _u} ^I}} {{{{ e} ^u} _J}}} = {\overset{I\downarrow J\rightarrow}{\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}}$
basis determinant: ${det(e)} = {1}$
${{{{ c} _a} _b} ^c} = {\overset{a\downarrow[{b\downarrow c\rightarrow}]}{\left[\begin{matrix} \overset{b\downarrow c\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]} \\ \overset{b\downarrow c\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}\end{matrix}\right]}}$
${{{ g} _u} _v} = {{{{{ e} _u} ^I}} {{{{ e} _v} ^J}} {{{{ \eta} _I} _J}}}$
${{{ g} _u} _v} = {\overset{u\downarrow v\rightarrow}{\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}}$
${{{ g} _u} _v} = {{{{{ e} _u} ^I}} {{{{ e} _v} ^J}} {{{{ \eta} _I} _J}}}$
metric determinant: ${det(g)} = {1}$
${{{{ \Gamma} _a} _b} _c} = {{{\frac{1}{2}}} {{\left({{{{{ g} _a} _b} _{,c}} + {{{{ g} _a} _c} _{,b}}{-{{{{ g} _b} _c} _{,a}}} + {{{{ c} _a} _b} _c} + {{{{ c} _a} _c} _b}{-{{{{ c} _c} _b} _a}}}\right)}}}$
commutation coefficients:
${c} = {\overset{a\downarrow[{b\downarrow c\rightarrow}]}{\left[\begin{matrix} \overset{b\downarrow c\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]} \\ \overset{b\downarrow c\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}\end{matrix}\right]}}$
metric:
${g} = {\overset{u\downarrow v\rightarrow}{\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}}$
metric inverse:
${g} = {\overset{a\downarrow b\rightarrow}{\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}}$
metric derivative:
${{\partial g}} = {\overset{a\downarrow[{b\downarrow c\rightarrow}]}{\left[\begin{matrix} \overset{b\downarrow c\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]} \\ \overset{b\downarrow c\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}\end{matrix}\right]}}$
1st kind Christoffel:
${\Gamma} = {\overset{a\downarrow[{b\downarrow c\rightarrow}]}{\left[\begin{matrix} \overset{b\downarrow c\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]} \\ \overset{b\downarrow c\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}\end{matrix}\right]}}$
connection coefficients / 2nd kind Christoffel:
${\Gamma} = {\overset{a\downarrow[{b\downarrow c\rightarrow}]}{\left[\begin{matrix} \left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right] \\ \left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]\end{matrix}\right]}}$
connection coefficients derivative:
${{\partial \Gamma}} = {\overset{a\downarrow b\rightarrow[{c\downarrow d\rightarrow}]}{\left[\begin{array}{cc} \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}& \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}\\ \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}& \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}\end{array}\right]}}$
connection coefficients squared:
${{(\Gamma^2)}} = {\overset{a\downarrow b\rightarrow[{c\downarrow d\rightarrow}]}{\left[\begin{array}{cc} \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}& \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}\\ \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}& \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}\end{array}\right]}}$
Riemann curvature, $\sharp\flat\flat\flat$:
${R} = {\overset{a\downarrow b\rightarrow[{c\downarrow d\rightarrow}]}{\left[\begin{array}{cc} \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}& \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}\\ \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}& \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}\end{array}\right]}}$
Riemann curvature, $\sharp\sharp\flat\flat$:
${R} = {\overset{a\downarrow b\rightarrow[{c\downarrow d\rightarrow}]}{\left[\begin{array}{cc} \left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]& \left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]\\ \left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]& \left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]\end{array}\right]}}$
Ricci curvature, $\sharp\flat$:
${R} = {\overset{a\downarrow b\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}}$
Gaussian curvature:
$0$
trace-free Ricci, $\sharp\flat$:
${{(R^{TF})}} = {\overset{a\downarrow b\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}}$
Einstein / trace-reversed Ricci curvature, $\sharp\flat$:
${G} = {\overset{a\downarrow b\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}}$
Schouten, $\sharp\flat$:
${P} = {\overset{a\downarrow b\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}}$
Weyl, $\sharp\sharp\flat\flat$:
${C} = {\overset{a\downarrow b\rightarrow[{c\downarrow d\rightarrow}]}{\left[\begin{array}{cc} \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}& \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}\\ \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}& \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}\end{array}\right]}}$
Weyl, $\flat\flat\flat\flat$:
${C} = {\overset{a\downarrow b\rightarrow[{c\downarrow d\rightarrow}]}{\left[\begin{array}{cc} \left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]& \left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]\\ \left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]& \left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]\end{array}\right]}}$
Plebanski, $\sharp\sharp\flat\flat$:
${P} = {\overset{a\downarrow b\rightarrow[{c\downarrow d\rightarrow}]}{\left[\begin{array}{cc} \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}& \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}\\ \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}& \overset{c\downarrow d\rightarrow}{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}\end{array}\right]}}$
divergence: ${{{{ A} ^i} _{,i}} + {{{{{{ \Gamma} ^i} _i} _j}} {{{ A} ^j}}}} = {{\frac{\partial {A^{\hat{x}}}}{\partial x}} + {\frac{\partial {A^{\hat{y}}}}{\partial y}}}$
geodesic:
${\overset{a\downarrow}{\left[\begin{matrix} \ddot{\hat{x}} \\ \ddot{\hat{y}}\end{matrix}\right]}} = {\overset{a\downarrow}{\left[\begin{matrix} 0 \\ 0\end{matrix}\right]}}$
parallel propagators:
${{[\Gamma_x]}} = {\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}$
$\int\limits_{{{x_L}}}^{{{x_R}}}{{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}}d x$
= $\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]$
${ P} _x$ = $\exp\left( -{\int\limits_{{{x_L}}}^{{{x_R}}}{{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}}d x}\right)$
= $\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]$
${{ P} _x}^{-1}$ = $\exp\left({\int\limits_{{{x_L}}}^{{{x_R}}}{{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}}d x}\right)$
= $\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]$
${{[\Gamma_y]}} = {\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}$
$\int\limits_{{{y_L}}}^{{{y_R}}}{{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}}d y$
= $\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]$
${ P} _y$ = $\exp\left( -{\int\limits_{{{y_L}}}^{{{y_R}}}{{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}}d y}\right)$
= $\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]$
${{ P} _y}^{-1}$ = $\exp\left({\int\limits_{{{y_L}}}^{{{y_R}}}{{\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}}d y}\right)$
= $\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]$
propagator commutation:
[ ${ P} _x$ , ${ P} _y$ ] = ${{{\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}} {{\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}}}{-{{{\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}} {{\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}}}}$ = $\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]$
propagator partials
${{\frac{\partial}{\partial x}}\left({\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}\right)} = {\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}$
${{\frac{\partial}{\partial y}}\left({\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}\right)} = {\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}$
${{\frac{\partial}{\partial x}}\left({\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}\right)} = {\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}$
${{\frac{\partial}{\partial y}}\left({\left[\begin{array}{cc} 1& 0\\ 0& 1\end{array}\right]}\right)} = {\left[\begin{array}{cc} 0& 0\\ 0& 0\end{array}\right]}$
volume element: $1$
volume integral: ${{\Delta x}} \cdot {{\Delta y}}$
finite volume (0,0)-form:
${{u(x_C, t_R)}} = {{{u(x_C, t_L)}} + {{{\Delta t}} \cdot {{\left({{{{\frac{1}{{\mathcal{V}(x_C)}}}} {{0}}} + {{S(x_C)}}}\right)}}}}$
${{u(x_C, t_R)}} = {{{u(x_C, t_L)}} + {{{\Delta t}} \cdot {{\left({{{{\frac{1}{{{\Delta x}} \cdot {{\Delta y}}}}} {{0}}} + {{S(x_C)}}}\right)}}}}$
${{u(x_C, t_R)}} = {{{u(x_C, t_L)}} + {{{\Delta t}} \cdot {{\left({{{{\frac{1}{{{\Delta x}} \cdot {{\Delta y}}}}} {{0}}} + {{S(x_C)}}}\right)}}}}$
${{u(x_C, t_R)}} = {{{u(x_C, t_L)}} + {{{{S(x_C)}}} \cdot {{\Delta t}}}}$