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mathematica notebook added

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tuturials/GW_tutorial_xAct_exercise.nb 0 → 100644
(* Content-type: application/vnd.wolfram.mathematica *)
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Cell[CellGroupData[{
Cell["PERTURBATIVE GRAVITY CALCULATIONS", "Title",
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StyleBox["is a collection of packages, organized hierarchically.",
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StyleBox[" is a package for efficient construction and manipulation of \
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symbols using ",
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metric and its derivatives using ",
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Cell[61523, 1536, 878, 23, 44, "Input",ExpressionUUID->"741acee4-2b50-4020-953c-2cec586fe0fe"]
}, Open ]]
}, Open ]]
}
]
*)
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