Metric symmetry by design in general relativity

The usual derivation of Einstein’s field equations from the Einstein–Hilbert action is performed by silently assuming the metric tensor’s symmetric character. If this symmetry is not assumed, the result is a new theory, such as Einstein’s attempted Unified Field Theory or Moffat’s Nonsymmetric Gravitational Theory. Explicitly enforcing the constraint by means of a Lagrange-multiplier term restores Einstein’s field equations, but the multiplier appears as an additional, unconstrained antisymmetric term. We briefly discuss the possible significance of this term with respect to a nonvanishing cosmological angular momentum, a sourced spin current, the nonsymmetric nature of the Einstein pseudotensor characterizing the energy–momentum of the gravitational field, and possible implications on attempts to obtain a quantum theory of gravity.