Extreme black hole uniqueness conjecture for multiple degenerate black holes

A singular harmonic map is associated with a collection of N>1N>1 distinct punctures on the zz-axis, at positions z=(z1,,zN)\mathbf{z}=(z_1,\ldots,z_N), with potential constants giving nonzero angular momenta Ji\mathcal{J}_i at each puncture. The tangent map parameters are denoted by bib_i, for i=1,,Ni=1,\ldots,N.

Extreme black hole uniqueness conjecture. At least one tangent map parameter must be nonzero:

there exists i{1,,N} such that bi0.\text{there exists }i\in\{1,\ldots,N\}\text{ such that }b_i\neq 0.

This is a PDE formulation of the claim that regular asymptotically flat multiple degenerate black hole solutions to the axisymmetric stationary vacuum Einstein equations do not exist. If all bib_i vanished, the associated stationary vacuum spacetime would have no conical singularities and would provide a counterexample to extreme black hole uniqueness.

Sources & referencesView supporting material

Primary source

Qing Han, Marcus Khuri, Gilbert Weinstein and Jingang Xiong, “The Mass-Angular Momentum Inequality for Multiple Black Holes”, arXiv:2501.15093 (2025).

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