[Commits] [svn:einsteintoolkit] Paper_EinsteinToolkit_2010/ (Rev. 12)
bcmsma at astro.rit.edu
bcmsma at astro.rit.edu
Mon Jan 24 11:13:56 CST 2011
User: bmundim
Date: 2011/01/24 11:13 AM
Modified:
/
ET.tex
Log:
First draft on the initial data section.
File Changes:
Directory: /
============
File [modified]: ET.tex
Delta lines: +63 -2
===================================================================
--- ET.tex 2011-01-24 17:06:57 UTC (rev 11)
+++ ET.tex 2011-01-24 17:13:56 UTC (rev 12)
@@ -373,8 +373,69 @@
\subsection{Initial Data}
-\todo{1/2 page Josh}
+\todo{1/2 page Josh, Bruno}
+The Einstein Toolkit contains many thorns used to generate initial data for GR simulations,
+including both vacuum and hydrodynamical configurations. These include thorns used primarily
+for testing out various components of the evolution scheme as well as physically motivated
+configurations that describe single of binary blacks and/or neutron stars. Many of the thorns
+are self-contained, consisting of either all the code to generate exact initial solutions or
+the numerical tools required to construct solutions known semi-analytically. Others, though,
+require the installation of other numerical software packages that are included in the toolkit
+as External libraries. The {\tt twopunctures} thorn \cite{Ansorg:2004ds}, commonly used in numerical
+relativity to generate binary black hole data, invokes the GNU Scientific Library [GSL; \cite{Galassi:2009}].
+Several thorns have also been implemented to read in datafiles generated by the
+{\tt Lorene code} \cite{Loreneweb,GGTMB}, including the BHBH, BHNS, and NSNS data made publicly
+available through the Lorene website.
+
+Scheduling of initial data routines generally follows a standard format. User-defined parameters
+are run through a parameter check designed to catch obvious internal inconsistencies, in addition to
+any known incompatibilities with other modules of the toolkit. Initial data is then generated
+at the proper stage within the Cactus framework, determined primarily by whether the configuration
+in question represents vacuum or a hydrodynamical configuration. Finally, any necessary cleanup
+is typically performed at the end of the initial step, prior to the iterations forward in time.
+
+For vacuum initial data configurations, an initial data thorn must supply $g_{ij}$, the spatial 3-metric,
+and $K_{ij}$, the extrinsic curvature. While the evolution scheme typically makes use of the BSSN formalism,
+the conversion between the physical and conformal metric and extrinsic curvature is handled solely within
+evolution thorns, and is not referenced by initial data ones. Optionally, many initial data thorns also
+supply values for the lapse and shift vector, and in some cases time derivatives as well, though these
+may be supplied by other routines depending on the freedom to choose gauge conditions envisioned for a
+specific configuration.
+
+For hydrodynamic configurations, assuming that an equation of state has been specified, the user must also
+supply the values of hydrodynamic variables at all grid locations, in particular the primitive variables
+$\rho$, $v_i$ and the energy variable $\epsilon$ for all cases where we don't have a polytype EOS in the
+form $P=P(\rho)$ (see Sec.~\ref{???} for a discussion of the use of EOS in the ET). For an MHD configuration,
+one must supply all of these along with the initial magnetic field $B^i$ as well.
+
+The initial data routines currently implemented include the following:
+\begin{itemize}
+\item Vacuum spacetime tests:
+\begin{enumerate}
+\item {\tt IDConstraintViolate}: A vacuum spacetime in which the diagonal terms in the spatial metric are
+modified by a spatial deformation to explicitly violate the Hamiltonian constraint.
+\item {\tt Exact}: A set of exact spacetimes in various coordinates, along with tools to Lorentz boost
+those configurations.
+\end{enumerate}
+\item Vacuum gravitational wave configurations:
+\begin{enumerate}
+\item {\tt IDBrillData}: A Brill wave spacetime \cite{Brill:1959}.
+\item {\tt IDLinearWaves}: A spacetime containing a linear gravitational wave.
+\end{enumerate}
+\item Black Hole configurations:
+\begin{enumerate}
+\item {\tt IDAnalyticBH}: This thorn can generate Schwarzchild black holes, as well as the Misner solution
+for multiple BHs and the brill-Lindquist binary BH solution.
+\item {\tt IDAxibrillBH,~IDAxiOddBrillBH}: These thorns generate single black holes deformed by even and
+odd parity axisymmetric perturbations, respectively.
+\item {\tt DistortedBHIVP,~RotatingDBHIVP}: These thorns generate single black holes distorted by even
+and odd-parity non-axisymmetric perturbation, respectivey.
+\item {\tt TwoPunctures}: This thorn generates accurate binary black-hole initial data.
+\end{enumerate}
+\end{itemize}
+
+
\paragraph{Gravitational Waves}
\paragraph{Black Holes}
@@ -424,7 +485,7 @@
\todo{2 pages in total, 1 plot per paragraph, Frank coordinates}
\paragraph{Kerr-Schild}
-\todo{1/2 page, who?}
+\todo{1/2 page, Bruno}
Show stable Kerr-evolution. What is commonly shown for this nowadays, the
spectrum of the ringdown of a perturbation?
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