What do quantum fields 'see' inside a charged black hole?

Inside a charged (Reissner-Nordström) black hole there are two horizons, and defining well-behaved quantum states across both has been technically fraught. Working in coordinates that pass smoothly through both horizons, the authors construct a specific quantum vacuum state for the Dirac (electron) field and prove it satisfies the Hadamard condition — the standard criterion that a quantum state behaves physically, with no spurious infinities in measurable quantities. This matters because well-defined quantum states near the Cauchy horizon are central to understanding whether strong cosmic censorship survives quantum corrections.