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I have an elementary confusion about black hole physics. The standard consensus is that if I fall into a black hole, at the horizon I don't see any violations of effective field theory for a large black hole. This is because the curvature at the horizon is of order $1/M^2$, where $M$ is the mass of the black hole, so I don't feel any large tidal forces.

However, suppose that I am a late-time observer, and that at very early times a particle fell into the horizon. In the near-horizon Rindler region, there is a huge relative boost between me and the early time particle. Assuming that we are the same mass and that we were released from rest at the same Schwarzschild radius with time separation $\Delta t$, our trajectories are related by a boost factor $\exp(\Delta t/(4M))$. This means that if $\Delta t$ is big enough, I see the early time particle moving at trans-Planckian energies.

Normally, I would think that a trans-Planckian excitation at early times is a violation of vacuum effective field theory. It is no longer safe to assume that the late-time field is in the vacuum state if there's a huge amount of energy at early times. Technically this will arise because propagators in loop diagrams will pass through the high-energy region, where it's no longer safe to use the Feynman propagator.

So, why can we assume that the late-time observer is in his vacuum state as he passes through the horizon?

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