3+1 formalism and bases of numerical relativity - LUTh ...
3+1 formalism and bases of numerical relativity - LUTh ...
3+1 formalism and bases of numerical relativity - LUTh ...
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Chapter 7<br />
Asymptotic flatness <strong>and</strong> global<br />
quantities<br />
Contents<br />
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103<br />
7.2 Asymptotic flatness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103<br />
7.3 ADM mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105<br />
7.4 ADM momentum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112<br />
7.5 Angular momentum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113<br />
7.6 Komar mass <strong>and</strong> angular momentum . . . . . . . . . . . . . . . . . . 116<br />
7.1 Introduction<br />
In this Chapter, we review the global quantities that one may associate to the spacetime (M,g)<br />
or to each slice Σt <strong>of</strong> the <strong>3+1</strong> foliation. This encompasses various notions <strong>of</strong> mass, linear<br />
momentum <strong>and</strong> angular momentum. In the absence <strong>of</strong> any symmetry, all these global quantities<br />
are defined only for asymptotically flat spacetimes. So we shall start by defining the notion <strong>of</strong><br />
asymptotic flatness.<br />
7.2 Asymptotic flatness<br />
The concept <strong>of</strong> asymptotic flatness applies to stellar type objects, modeled as if they were alone<br />
in an otherwise empty universe (the so-called isolated bodies). Of course, most cosmological<br />
spacetimes are not asymptotically flat.