Quantum kicks near a Cauchy horizon

We analyze a quantum observer who falls geodesically toward the Cauchy horizon of (1 + 1)-dimensional eternal black hole spacetime with global structure non-extremal Reissner–Nordström solution. The interacts massless scalar field, using an Unruh–DeWitt detector coupled linearly to proper time derivative and by measuring local energy density field. Taking field be initially prepared in Hartle–Hawking–Israel (HHI) state or Unruh state, we find that both detector's transition rate generically diverge on approaching horizon, respectively, proportionally inverse square divergences one branches are independent surface gravities. When outer inner horizons have equal gravities, disappear altogether HHI for state. conjecture, grounds comparison Rindler 1 3 Minkowski spacetimes, similar properties hold dimensions but logarithmic rather than power-law divergence.