Carminati–McLenaghan invariants

In general relativity, the Carminati–McLenaghan invariants or CM scalars are a set of 16 scalar curvature invariants for the Riemann tensor. This set is usually supplemented with at least two additional invariants.

The CM invariants consist of 6 real scalars plus 5 complex scalars, making a total of 16 invariants. They are defined in terms of the Weyl tensor ${\displaystyle C_{abcd}}$ and its right (or left) dual ${\displaystyle {{}^{\star }C}_{ijkl}=(1/2)\epsilon _{klmn}C_{ij}{}^{mn}}$, the Ricci tensor ${\displaystyle R_{ab}}$, and the trace-free Ricci tensor

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