Birkhoff's theorem (relativity)

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Front page of Arkiv för Matematik, Astronomi och Fysik where Jebsen's work was published

In

asymptotically flat. This means that the exterior solution (i.e. the spacetime outside of a spherical, nonrotating, gravitating body) must be given by the Schwarzschild metric. The converse of the theorem is true and is called Israel's theorem.[1][2] The converse is not true in Newtonian gravity.[3][4]

The theorem was proven in 1923 by George David Birkhoff (author of another famous Birkhoff theorem, the pointwise ergodic theorem which lies at the foundation of ergodic theory). In 2005, Nils Voje Johansen, Finn Ravndal, Stanley Deser[citation needed] stated that the theorem was allegedly published two years earlier by a little-known Norwegian physicist, Jørg Tofte Jebsen.[5][6][non-primary source needed][original research?]

Intuitive rationale

The intuitive idea of Birkhoff's theorem is that a spherically symmetric gravitational field should be produced by some massive object at the origin; if there were another concentration of

gravitation in the Newtonian limit
.

Implications

The conclusion that the exterior field must also be stationary is more surprising, and has an interesting consequence. Suppose we have a spherically symmetric star of fixed mass which is experiencing spherical pulsations. Then Birkhoff's theorem says that the exterior geometry must be Schwarzschild; the only effect of the pulsation is to change the location of the

gravitational waves, which requires at least a mass quadrupole structure.[7]

Generalizations

Birkhoff's theorem can be generalized: any spherically symmetric and asymptotically flat solution of the

Einstein/Maxwell field equations
, without , must be static, so the exterior geometry of a spherically symmetric charged star must be given by the
Reissner–Nordström electrovacuum. In the Einstein-Maxwell theory, there exist spherically symmetric but not asymptotically flat solutions, such as the Bertotti-Robinson universe.

See also

References

  1. – via American Physical Society.
  2. .
  3. .
  4. .
  5. ^ J.T. Jebsen, Über die allgemeinen kugelsymmetrischen Lösungen der Einsteinschen Gravitationsgleichungen im Vakuum, Arkiv för matematik, astronomi och fysik, 15 (18), 1 - 9 (1921).
  6. ^ J.T. Jebsen, On the general symmetric solutions of Einstein's gravitational equations in vacuo, General Relativity and Cosmology 37 (12), 2253 - 2259 (2005).
  7. S2CID 116755736
    .

External links