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Holographic Space-Time Does Not Predict Firewalls

T. Banks, W. Fischler

TL;DR

This paper challenges the AMPS firewall claim by deploying the Holographic Space-Time framework, which uses many observer-specific Hilbert spaces connected by overlap constraints. It argues that old black holes host a large horizon DOF that decouples from interior particle DOF for times of order the Schwarzschild radius, preserving particle physics without a firewall. The analysis shows that firewall-like behavior does not emerge once the correct multi-Hilbert-space structure and entropy deficits of particle DOF are accounted for, while Hawking radiation is explained via horizon DOF converting to asymptotic particles in a unitary evolution. Overall, HST provides a thermodynamically consistent, unitary description of evaporating black holes without invoking firewalls, highlighting a key conceptual difference from single-Hilbert-space QG models. The work underscores the importance of observer-dependent descriptions and horizon DOF in resolving the firewall paradox.

Abstract

We use the formalism of Holographic Space-time (HST) to investigate the claim of [1] that old black holes contain a firewall, i.e. an in-falling observer encounters highly excited states at a time much shorter than the light crossing time of the Schwarzschild radius. This conclusion is much less dramatic in HST than in the hypothetical models of quantum gravity used in [1]. In HST there is no dramatic change in particle physics inside the horizon until a time of order the Schwarzschild radius.

Holographic Space-Time Does Not Predict Firewalls

TL;DR

This paper challenges the AMPS firewall claim by deploying the Holographic Space-Time framework, which uses many observer-specific Hilbert spaces connected by overlap constraints. It argues that old black holes host a large horizon DOF that decouples from interior particle DOF for times of order the Schwarzschild radius, preserving particle physics without a firewall. The analysis shows that firewall-like behavior does not emerge once the correct multi-Hilbert-space structure and entropy deficits of particle DOF are accounted for, while Hawking radiation is explained via horizon DOF converting to asymptotic particles in a unitary evolution. Overall, HST provides a thermodynamically consistent, unitary description of evaporating black holes without invoking firewalls, highlighting a key conceptual difference from single-Hilbert-space QG models. The work underscores the importance of observer-dependent descriptions and horizon DOF in resolving the firewall paradox.

Abstract

We use the formalism of Holographic Space-time (HST) to investigate the claim of [1] that old black holes contain a firewall, i.e. an in-falling observer encounters highly excited states at a time much shorter than the light crossing time of the Schwarzschild radius. This conclusion is much less dramatic in HST than in the hypothetical models of quantum gravity used in [1]. In HST there is no dramatic change in particle physics inside the horizon until a time of order the Schwarzschild radius.

Paper Structure

This paper contains 3 sections, 5 equations, 2 figures.

Table of Contents

  1. Introduction
  2. HST, Sketchily
  3. Are there firewalls in HST?

Figures (2)

  • Figure 1: The trajectory E, which falls into a black hole shortly after its horizon forms. Causal diamonds are shown along this trajectory for certain of the times mentioned in the text. When $\epsilon \sim N_E$ the trajectory hits the singularity. The diamond described by the Hilbert space ${\cal H}_{E\ in} (T_{HE} + \epsilon )$ lies inside the purple black hole interior and its past boundary is indicated in red.
  • Figure 2: This diagram shows both E and L and their overlap. Since the time spanned is of order the Page time, the radius of the horizon (boundary of the blue region) changes between the times at which the two trajectories cross it. The overlap ${\cal O}$ describes the region outlined in green.