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author | jthorn <jthorn@e296648e-0e4f-0410-bd07-d597d9acff87> | 2002-05-12 15:03:19 +0000 |
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committer | jthorn <jthorn@e296648e-0e4f-0410-bd07-d597d9acff87> | 2002-05-12 15:03:19 +0000 |
commit | fc915102f9483db60266d9bb719223bdeb7d7ff0 (patch) | |
tree | 82bafdd2c43a3085c5d350fa656bc277ef83a608 /doc | |
parent | fd4a87f87c975a360d694af9c1913d39e196d7fd (diff) |
document Hisa-aki Shinkai's Kastor-Traschen maximally charged multiple BHs
solution
git-svn-id: http://svn.einsteintoolkit.org/cactus/EinsteinInitialData/Exact/trunk@66 e296648e-0e4f-0410-bd07-d597d9acff87
Diffstat (limited to 'doc')
-rw-r--r-- | doc/documentation.tex | 56 |
1 files changed, 50 insertions, 6 deletions
diff --git a/doc/documentation.tex b/doc/documentation.tex index d1591a3..791378b 100644 --- a/doc/documentation.tex +++ b/doc/documentation.tex @@ -80,7 +80,7 @@ parameter: \item[{\tt "fakebinary"}] Thorne's ``fake binary'' approximate spacetime \item[{\tt "multiBH"}] - Maximally charged multi BH solutions + Kastor-Traschen Maximally charged multi BH solutions \end{description} \item[Cosmological spacetimes]\mbox{}\\[-\baselineskip] \begin{description} @@ -395,9 +395,51 @@ black hole's center; the default setting should be ok for most purposes. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -\subsection{Maximally Charged Multi-BH Solutions} +\subsection{Kastor-Traschen Maximally Charged Multi-BH Solutions} -FIXME: get more info from Hisa-aki +\verb|Exact::exactmodel = "multiBH"| specifies the Kastor-Traschen (KT) +solution. The file \verb|KTsol.tex| in the documentation directory +of this thorn gives more details/references about this solution and +the realated Majumdar-Papapetrou (MP) solution. + +Basically, the Kastor-Traschen solution is a multi-black-hole solution +to Einstein's equation with cosmological constant, containing arbitrarily +many maximally charged ($Q=M$) quasi-Schwarzschild black holes that +participate in an overall de Sitter expansion or contraction. (It +vaguely resembles a cosmological generalization of the Brill-Lindquist +initial data.) In the $\Lambda \rightarrow 0$ limit, the KT solutions +reduce to the MP solution. + +To write the KT metric, we first choose $(x_i, y_i, z_i) \in \Re^3$, +$i=1,2,\cdots,N$ for locations of black holes. Then the line element is +\begin{equation} +ds^2=-\frac{1}{\Omega^2} dt^2+a(t)^2 \Omega^2(dx^2+dy^2+dz^2) +\end{equation} +where +\begin{align} +\Omega &= 1+\sum_{i=1}^N {\frac{M_i}{a r_i}} \\ +a &= e^{Ht} \\ +H &= \pm \sqrt{\frac{\Lambda}{3}} \\ +r_i &= \sqrt{(x-x_i)^2 + (y-y_i)^2 + (z-z_i)^2} %%%\\ +\end{align} +We interpret $M_i$ as the mass of the $i{\rm th}$ black hole, +although we have neither an asymptotically flat region nor event +horizons available to convert this naive interpretation into a rigorous +one. + +This thorn supports up to 4~black holes; the physics parameters are +\begin{align} +N & = \text{\tt KT\_nBH} \\ +H & = \text{\tt KT\_Hubble} %%%\\ +\end{align} +and +\begin{align} +M_i & = \text{\tt m\_bh$i$} \\ +x_i & = \text{\tt co\_bh$i$x} \\ +y_i & = \text{\tt co\_bh$i$y} \\ +z_i & = \text{\tt co\_bh$i$z} %%%\\ +\end{align} +for each $i = 1$, $2$, $3$, $4$. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% @@ -636,9 +678,11 @@ These parameters are useful to hide the spherical symmetry of the metric. \section{Acknowledgments} Many different people have contributed code to this thorn. -Jonathan Thornburg wrote this documentation in May 2002 based on -the comments in the code, some reverse-engineering, and querying -various people about how the code works. +Jonathan Thornburg wrote most of this documentation in May 2002 based +on the comments in the code, some reverse-engineering, and querying +various people about how the code works. The description of the +Kastor-Traschen maximally charged multi-BH solutions is adapted from +the file \verb|KTsol.tex| in this same directory, by Hisa-aki Shinkai. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |