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3+1 formalism and bases of numerical relativity - LUTh ...

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Contents<br />

1 Introduction 11<br />

2 Geometry <strong>of</strong> hypersurfaces 15<br />

2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15<br />

2.2 Framework <strong>and</strong> notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15<br />

2.2.1 Spacetime <strong>and</strong> tensor fields . . . . . . . . . . . . . . . . . . . . . . . . . . 15<br />

2.2.2 Scalar products <strong>and</strong> metric duality . . . . . . . . . . . . . . . . . . . . . . 16<br />

2.2.3 Curvature tensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18<br />

2.3 Hypersurface embedded in spacetime . . . . . . . . . . . . . . . . . . . . . . . . . 19<br />

2.3.1 Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19<br />

2.3.2 Normal vector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21<br />

2.3.3 Intrinsic curvature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22<br />

2.3.4 Extrinsic curvature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23<br />

2.3.5 Examples: surfaces embedded in the Euclidean space R 3 . . . . . . . . . . 24<br />

2.4 Spacelike hypersurface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28<br />

2.4.1 The orthogonal projector . . . . . . . . . . . . . . . . . . . . . . . . . . . 29<br />

2.4.2 Relation between K <strong>and</strong> ∇n . . . . . . . . . . . . . . . . . . . . . . . . . 31<br />

2.4.3 Links between the ∇ <strong>and</strong> D connections . . . . . . . . . . . . . . . . . . . 32<br />

2.5 Gauss-Codazzi relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34<br />

2.5.1 Gauss relation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34<br />

2.5.2 Codazzi relation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36<br />

3 Geometry <strong>of</strong> foliations 39<br />

3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39<br />

3.2 Globally hyperbolic spacetimes <strong>and</strong> foliations . . . . . . . . . . . . . . . . . . . . 39<br />

3.2.1 Globally hyperbolic spacetimes . . . . . . . . . . . . . . . . . . . . . . . . 39<br />

3.2.2 Definition <strong>of</strong> a foliation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40<br />

3.3 Foliation kinematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41<br />

3.3.1 Lapse function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41<br />

3.3.2 Normal evolution vector . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42<br />

3.3.3 Eulerian observers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42<br />

3.3.4 Gradients <strong>of</strong> n <strong>and</strong> m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44<br />

3.3.5 Evolution <strong>of</strong> the 3-metric . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

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