# The subtle unphysical hypothesis of the firewall theorem

## TL;DR

This paper critically examines the assumptions behind the black-hole firewall theorem, identifying a likely unrealistic hypothesis and clarifying conceptual confusions related to entropy and entropy bounds.

## Contribution

It highlights a specific unrealistic assumption in the firewall theorem and clarifies the conceptual errors involving entropy notions and bounds.

## Key findings

- Identifies the likely unrealistic hypothesis in the firewall theorem
- Clarifies the confusion between different entropy notions
- Points out misuse of the entropy bound in the theorem

## Abstract

The black-hole firewall theorem derives a suspicious consequence (large energy-momentum density on the horizon of a black hole) from a set of seemingly reasonable hypotheses. I point out the hypothesis which is likely to be unrealistic---a hypothesis not always sufficiently made explicit--- and discuss the subtle confusion at its origin: mixing-up of two different notions of entropy and misusing of the entropy bound.