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

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CONTENTS 5<br />

6 Conformal decomposition 83<br />

6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83<br />

6.2 Conformal decomposition <strong>of</strong> the 3-metric . . . . . . . . . . . . . . . . . . . . . . 85<br />

6.2.1 Unit-determinant conformal “metric” . . . . . . . . . . . . . . . . . . . . 85<br />

6.2.2 Background metric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85<br />

6.2.3 Conformal metric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86<br />

6.2.4 Conformal connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88<br />

6.3 Expression <strong>of</strong> the Ricci tensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89<br />

6.3.1 General formula relating the two Ricci tensors . . . . . . . . . . . . . . . 90<br />

6.3.2 Expression in terms <strong>of</strong> the conformal factor . . . . . . . . . . . . . . . . . 90<br />

6.3.3 Formula for the scalar curvature . . . . . . . . . . . . . . . . . . . . . . . 91<br />

6.4 Conformal decomposition <strong>of</strong> the extrinsic curvature . . . . . . . . . . . . . . . . . 91<br />

6.4.1 Traceless decomposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91<br />

6.4.2 Conformal decomposition <strong>of</strong> the traceless part . . . . . . . . . . . . . . . . 92<br />

6.5 Conformal form <strong>of</strong> the <strong>3+1</strong> Einstein system . . . . . . . . . . . . . . . . . . . . . 95<br />

6.5.1 Dynamical part <strong>of</strong> Einstein equation . . . . . . . . . . . . . . . . . . . . . 95<br />

6.5.2 Hamiltonian constraint . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98<br />

6.5.3 Momentum constraint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98<br />

6.5.4 Summary: conformal <strong>3+1</strong> Einstein system . . . . . . . . . . . . . . . . . . 98<br />

6.6 Isenberg-Wilson-Mathews approximation to General Relativity . . . . . . . . . . 99<br />

7 Asymptotic flatness <strong>and</strong> global quantities 103<br />

7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103<br />

7.2 Asymptotic flatness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103<br />

7.2.1 Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104<br />

7.2.2 Asymptotic coordinate freedom . . . . . . . . . . . . . . . . . . . . . . . . 105<br />

7.3 ADM mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105<br />

7.3.1 Definition from the Hamiltonian formulation <strong>of</strong> GR . . . . . . . . . . . . . 105<br />

7.3.2 Expression in terms <strong>of</strong> the conformal decomposition . . . . . . . . . . . . 108<br />

7.3.3 Newtonian limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110<br />

7.3.4 Positive energy theorem . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111<br />

7.3.5 Constancy <strong>of</strong> the ADM mass . . . . . . . . . . . . . . . . . . . . . . . . . 111<br />

7.4 ADM momentum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112<br />

7.4.1 Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112<br />

7.4.2 ADM 4-momentum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112<br />

7.5 Angular momentum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113<br />

7.5.1 The supertranslation ambiguity . . . . . . . . . . . . . . . . . . . . . . . . 113<br />

7.5.2 The “cure” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114<br />

7.5.3 ADM mass in the quasi-isotropic gauge . . . . . . . . . . . . . . . . . . . 115<br />

7.6 Komar mass <strong>and</strong> angular momentum . . . . . . . . . . . . . . . . . . . . . . . . . 116<br />

7.6.1 Komar mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116<br />

7.6.2 <strong>3+1</strong> expression <strong>of</strong> the Komar mass <strong>and</strong> link with the ADM mass . . . . . 119<br />

7.6.3 Komar angular momentum . . . . . . . . . . . . . . . . . . . . . . . . . . 121

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