What does the mass represent in the Schwarzschild metric for vacuum solutions?

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Discussion Overview

The discussion revolves around the interpretation of the mass term in the Schwarzschild metric, particularly in the context of vacuum solutions to Einstein's equations. Participants explore the implications of the mass term despite the vacuum condition (T_{ab}=0) and its relevance to spherically symmetric, stationary objects.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions the meaning of the mass in the Schwarzschild metric, asking whose mass it represents and how it fits into the vacuum solution context.
  • Another participant explains that the Schwarzschild metric is a solution to the vacuum Einstein equations for a spherically symmetric, stationary mass, suggesting that the mass term represents the total mass-energy of the central object.
  • A further contribution clarifies that the Schwarzschild solution can be viewed as a solution of empty space "up to one point," indicating a singularity at r=0, where the energy-momentum tensor becomes infinite.
  • Another analogy is provided, comparing the gravitational effects outside a massive object to the electric field outside a charged object, emphasizing that while the stress-energy tensor is zero outside the mass, gravitational effects still exist.
  • One participant challenges the previous point about singularities, asserting that the Schwarzschild solution applies to all spherically symmetric massive bodies and that the singularity is a special case.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of the mass term and the implications of singularities in the Schwarzschild solution. There is no consensus on these points, and the discussion remains unresolved.

Contextual Notes

Participants highlight the dependence on definitions of mass and the conditions under which the Schwarzschild solution is applicable, particularly regarding the nature of singularities and the interpretation of vacuum solutions.

physicslover8
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Sorry if I am asking a too trivial question! I am having a confusion regarding the following-The solution to Einstein equation in vacuum is given by the Schwarzschild metric. However, what does the mass represent in the metric in Schwarzschild coordinate? Whose mass is it and how does it enter although we are looking for vacuum solutions, meaning T_{ab}=0
 
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The Schwarzschild metric is one particular solution to the vacuum Einstein equations for the particular case of one spherically symmetric, stationary (non-rotating), uncharged mass. There are other solutions to the vacuum field equations (e.g. Kerr metric). The mass term is a boundary value representing the total mass-energy of the central object.
 
To be more precise, the Schwarzschild solution is a solution of empty space "up to one point". You could see it as the solution of which the energy momentum tensor is given by

[tex] T_{\mu\nu} = \rho \delta_{\mu}^0 \delta_{\nu}^0 \delta^4 (r)[/tex]

where rho is some mass density. With other words: if [itex]r \neq 0[/itex] then [itex]T_{\mu\nu} = 0[/itex], whereas for r=0 one has that [itex]T_{\mu\nu} \rightarrow \infty[/itex] indicating a singularity.
 
Or rather, the Schwarzschild solution is valid outside any massive, spherically symmetric object. A good analogy would be to the electric field outside a ball of charge. Outside the ball, there is no charge density, but there is an electric field from the ball. Similarly, outside a massive, spherically symmetric object, there are still effects from gravity, but the stress-energy tensor is zero.
 
haushofer said:
To be more precise, the Schwarzschild solution is a solution of empty space "up to one point" ... indicating a singularity.
No.

As Muphrid says
Muphrid said:
the Schwarzschild solution is valid outside any massive, spherically symmetric object.
the Schwarzschild solution is applicable for all for spherically symmetric massive bodies; the the singularity is only a special case
 

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