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@@ -117,18 +117,18 @@
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\begin{frame}{Methods on evolving black holes: moving puncture}
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In the isotropic coordinate for Schwarzschild black hole, the spical metric
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\begin{equation*}
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\begin{equation}
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\dd{l^2} = \left( 1+\frac{M}{2r} \right)^4 (\dd{r^2} + r^2 \dd{\Omega^2})
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\end{equation*}
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\end{equation}
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is conformally flat, with the conformal factor
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\begin{equation*}
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\begin{equation}
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\psi = 1 + \frac{M}{2r}.
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\end{equation*}
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\end{equation}
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General $N$ black hole puncture initial data:
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\begin{equation*}
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\begin{equation}
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\psi = \sum_{i=1}^N \frac{M_i}{2|\myvec{r}-\myvec{r}_i|} + (\text{regular part}),
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\end{equation*}
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\end{equation}
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again, if we factor out the conformal factor $\psi$, the remaining conformal metric is regular everywhere.
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\end{frame}
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@@ -168,13 +168,13 @@
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\begin{frame}{Discontinuous Galerkin method and \texttt{nmesh}}
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Core idea of DG method: if we have a first-order PDE system:
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\begin{equation*}
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\begin{equation}
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\pdvt{u} + A^i \pdv{u}{x^i} = S,
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\end{equation*}
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\end{equation}
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then for some test functions $\{v_a\}$, we have
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\begin{equation*}
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\begin{equation}
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\left(v_a, \pdvt{u}\right) + \left(v_a, A^i \pdv{u}{x^i}\right) = (v_a, S),
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\end{equation*}
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\end{equation}
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which reduce to a linear system of $\{ u_a = (v_a, u)\}$ after intergrating by parts. Boundary terms are replaced by numerical fluxes.
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In \texttt{nmesh}, we use Lagrange polynomials over Gauss-Legendre points on each element.
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@@ -236,8 +236,12 @@
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$\implies$ we need to find a first order, strongly hyperbolic formulation of Einstein's equations with constraint damping and compatible with the moving puncture gauge condition.
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\end{frame}
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\begin{frame}{Searching for a first order Z4c}{Hyperbolicity of first order systems}
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\begin{frame}{Searching for a first order Z4c}{Why Z4c?}
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\section{Searching for a first order Z4c}
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\subsection{Why Z4c?}
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\end{frame}
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\begin{frame}{Searching for a first order Z4c}{Hyperbolicity of first order systems}
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\subsection{Hyperbolicity of first order systems}
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Say we have a list of variables $u^I$, and a first order PDE system
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\begin{equation}
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