[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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