Strong Cosmic Censorship at the VCS Boundary: Inverted Polarity, Charge-Spin Duality, and Kerr-Newman-de Sitter

Penrose's strong cosmic censorship conjecture (SCC) asserts that the maximal Cauchy development of generic initial data for Einstein's equations is inextendible. Unlike weak cosmic censorship (WCC), which asks whether horizons form, SCC asks whether singularities are "strong enough" to prevent extension past the Cauchy horizon. Hintz and Vasy [1] showed that SCC can fail for Kerr-de Sitter black holes when the cosmological decay rate \(\alpha\) exceeds the Cauchy horizon blueshift \(\kappa_-\).

We analyze SCC through the Vorticity-Controlled System (VCS) framework [2], revealing six structural insights:

1. Inverted polarity. SCC is an inverted VCS: dissipation (cosmological \(\Lambda\)-decay) enables pathology (SCC failure), reversing the normal VCS paradigm where dissipation prevents pathology. The Hintz-Vasy criterion \(\alpha > \kappa_-\) is the inverted analogue of the VCS condition \(\delta > \gamma\).

2. Charge-spin duality. The Reissner-Nordström-de Sitter (RNdS) black hole provides a second inverted VCS instance. Both Kerr-dS (spin \(a^\)) and RNdS (charge \(q^ = Q/M\)) exhibit SCC failure near extremality via the same mechanism: \(\kappa_- \to 0\) while \(\alpha\) remains bounded below. The dimensionless parameters \(a^\) and \(q^\) are algebraically interchangeable in the SCC VCS.

3. Kerr-Newman-de Sitter. The combined case with both spin \(a^\) and charge \(q^\) is analyzed for the first time in the VCS framework. The extremality condition becomes \(a^{2} + q^{2} = 1\) — a quarter-circle in parameter space. Spin and charge cooperate: a moderately spinning, moderately charged black hole can reach near-extremality (and trigger SCC failure) even when neither parameter alone would approach its individual threshold. The SCC failure region is genuinely two-dimensional, strictly larger than the union of the Kerr-dS and RNdS failure strips.

4. Complementary fragility. Near extremality with \(\Lambda > 0\), WCC and SCC cannot both be strongly satisfied. A small WCC margin forces \(\kappa_- \to 0\), which — for any \(\alpha > 0\) — triggers SCC failure. Spin-charge cooperation amplifies this: the combined KNdS fragility threshold is lower than either individual threshold.

5. Rotation as SCC shield. The spectral gap \(\alpha\) is a multi-channel minimum over three QNM families. Rotating black holes possess near-horizon modes with damping rate \(\alpha_{\text{NH}} = \tfrac{1}{2}\kappa_+ < \kappa_-\), which automatically protect SCC. Charged-only black holes lack this channel — explaining the Davey et al. [8] observation that SCC holds for Kerr-dS but fails for RNdS. The algebraic charge-spin duality is broken by the mode spectrum.

6. Superradiance duality. The rotation shield and superradiance share the sam