Existence of solutions to Einstein's equation

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SUMMARY

The discussion centers on the relationship between the conservation of the energy-momentum tensor and the existence of solutions to Einstein's equations in general relativity. It is established that if the energy-momentum tensor is not conserved, then solutions to Einstein's equations do not exist. Conversely, the question arises whether the conservation of the energy-momentum tensor guarantees the existence of solutions. The challenge lies in proving this relationship, particularly since the metric tensor influences the covariant derivative that defines energy-momentum conservation.

PREREQUISITES
  • Understanding of Einstein's equations in general relativity
  • Familiarity with the energy-momentum tensor and its conservation laws
  • Knowledge of covariant derivatives and their role in differential geometry
  • Basic principles of electrodynamics and its conservation properties
NEXT STEPS
  • Research the implications of Bianchi identities in general relativity
  • Study the role of the metric tensor in defining covariant derivatives
  • Explore proofs of the existence of solutions to Einstein's equations under various conditions
  • Investigate the relationship between classical physics conservation laws and general relativity
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The discussion is beneficial for physicists, mathematicians, and students of general relativity who are exploring the foundational aspects of Einstein's equations and the conservation of energy-momentum in gravitational contexts.

causalset
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It is easy to see, from bianchi identities, that if energy-momentum tensor is not conserved, then Einstein's equation does not have a solution. But is there a proof that if energy momentum tensor IS conserved then Einstein's equation ALWAYS have a solution?
 
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I wonder: how do we know the energy-momentum tensor is conserved until we have a solution, since the metric enters the covariant derivative which defines energy momentum conservation?
 
atyy said:
I wonder: how do we know the energy-momentum tensor is conserved until we have a solution, since the metric enters the covariant derivative which defines energy momentum conservation?

What I meant is this: if we have some physics (such as electrodynamics) which is conserved WITHOUT gravity, then the solution continues to exist after we add gravity to it. My question is: how can you prove that is the case?
 

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