= Majumdar–Papapetrou solution
{c}
{title2=$ds^2=-H^{-2}dt^2+H^2d\mathbf x^2$}
The four-dimensional <Majumdar–Papapetrou solution> is a static multi-black-hole Einstein-Maxwell solution with $H=1+\sum_iM_i/|\mathbf x-\mathbf x_i|$ and positive geometrized masses $M_i$. The electromagnetic potential can be written $A=\pm(H^{-1}-1)dt$, with a common sign of charge. Its mass at infinity is $\sum_iM_i$. Each distinct centre is an extremal horizon of zero surface gravity rather than a pointlike naked metric singularity.
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