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arxiv: 2509.19451 · v2 · submitted 2025-09-23 · 🌀 gr-qc · astro-ph.HE· hep-th· physics.optics

Total absorption of tailored incoming signals by black holes

Furkan Tuncer , Vitor Cardoso , Rodrigo Panosso Macedo , Thomas F. M. Spieksma This is my paper

Pith reviewed 2026-05-18 14:11 UTC · model grok-4.3

classification 🌀 gr-qc astro-ph.HEhep-thphysics.optics
keywords black holesgravitational scatteringtotal absorptionresonancesvirtual absorptiontime-dependent signalshigher dimensionstotal transmission modes
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The pith

Tailored time modulations let black holes absorb incoming signals with no reflection for the full scattering duration.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows that resonances in the complex plane can be excited by specific temporal modulations of an incoming wave. This produces complete absorption by black holes or stars throughout the interaction. A reader would care because it implies these objects can store energy efficiently without scattering any back. The stored energy later escapes through relaxation into virtual absorption modes. Higher-dimensional black holes support a richer collection of these modes than four-dimensional ones.

Core claim

Resonances in the complex plane can be excited via tailored time-dependent scattering, leading to complete absorption for the entire duration of the scattering process. This makes stars and black holes truly black. Energy is stored with high efficiency and released once the process finishes via relaxation into the characteristic virtual absorption modes, also known as total transmission modes. Four-dimensional black holes have a restricted set of solutions, while higher-dimensional black holes exhibit a complex and interesting structure of virtual absorption modes.

What carries the argument

Virtual absorption modes (total transmission modes), which are complex-plane resonances matched exactly by a chosen time-dependent incoming waveform to achieve perfect absorption during scattering.

Load-bearing premise

Complex-plane resonances exist that can be matched by a physically realizable time-dependent waveform without infinite precision or unphysical amplitudes.

What would settle it

Numerical evolution of a precisely modulated wave packet scattering off a black hole spacetime, checking for zero reflected amplitude during the interaction followed by ringing in the predicted virtual absorption modes.

Figures

Figures reproduced from arXiv: 2509.19451 by Furkan Tuncer, Rodrigo Panosso Macedo, Thomas F. M. Spieksma, Vitor Cardoso.

Figure 1
Figure 1. Figure 1: FIG. 1. Scattering of a Gaussian pulse off a rectangular bar [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Energy content of a region where a double-barrier [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Scattering of VA waves off a ultracompact object ( [PITH_FULL_IMAGE:figures/full_fig_p004_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6 [PITH_FULL_IMAGE:figures/full_fig_p007_6.png] view at source ↗
read the original abstract

We uncover a new class of phenomena in gravitational physics, whereby resonances in the complex plane can be excited via tailored time-dependent scattering. We show that specific forms of temporal modulation of an incoming signal can lead to complete absorption for the entire duration of the scattering process. This, then, makes stars and black holes truly black. Such ``virtual absorption'' stores energy with high efficiency, releasing it once the process finishes via relaxation into the characteristic virtual absorption modes -- also known as total transmission modes -- of the object. While such modes are challenging to obtain and four-dimensional black holes have a restricted set of solutions, we also show that higher dimensional black holes have a complex and interesting structure of virtual absorption modes.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The manuscript claims that resonances in the complex plane can be excited through tailored temporal modulation of incoming signals, resulting in complete absorption by black holes and stars for the full duration of the scattering process. This 'virtual absorption' stores energy efficiently before release via relaxation into virtual absorption modes (also termed total transmission modes). The work notes that four-dimensional black holes have a restricted set of such modes while higher-dimensional black holes possess a richer structure.

Significance. If the central claim is established with physically realizable waveforms, the result would introduce a new mechanism for perfect absorption in gravitational scattering, with potential implications for black-hole perturbation theory and gravitational-wave interactions. The discussion of higher-dimensional mode structure adds interest, though the assessment of significance is tempered by the absence of explicit derivations or numerical demonstrations in the provided text.

major comments (2)
  1. [Abstract] Abstract: the assertion that specific temporal modulations achieve 'complete absorption for the entire duration' rests on exact excitation of complex-frequency virtual absorption modes. These modes are defined with outgoing boundary conditions at infinity, so their time-domain realization requires an exponentially growing precursor as t → −∞. This growth implies either infinite energy or an unphysical infinite past, directly challenging the physical realizability of the claimed finite, causal scattering process.
  2. [Higher-dimensional black holes] Higher-dimensional black holes section: while a richer mode spectrum is reported, the horizon ingoing / infinity outgoing boundary conditions that generate the complex poles remain unchanged. It is therefore unclear how the additional modes remove the time-asymmetry that forces exponentially growing incoming signals, leaving the central claim of total absorption vulnerable to the same realizability objection.
minor comments (1)
  1. The distinction between 'virtual absorption modes' and standard quasinormal modes should be stated explicitly with their respective boundary conditions at the first mention, rather than relying on the parenthetical 'also known as total transmission modes'.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and the insightful comments regarding physical realizability. We address each point below and have revised the text to better delineate the assumptions underlying our claims.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the assertion that specific temporal modulations achieve 'complete absorption for the entire duration' rests on exact excitation of complex-frequency virtual absorption modes. These modes are defined with outgoing boundary conditions at infinity, so their time-domain realization requires an exponentially growing precursor as t → −∞. This growth implies either infinite energy or an unphysical infinite past, directly challenging the physical realizability of the claimed finite, causal scattering process.

    Authors: We agree that exact excitation of the virtual absorption modes, which satisfy outgoing boundary conditions at infinity, formally requires an exponentially growing incoming component as t → −∞. Our analysis focuses on the finite-duration scattering interval during which the tailored modulation produces complete absorption. In the revised manuscript we have clarified this scope in the abstract and added a dedicated paragraph discussing practical approximations via truncated precursors, the associated finite energy cost for any chosen cutoff, and the resulting small initial transient. These changes make explicit that the central claim applies to the primary interaction period rather than an idealized infinite past. revision: yes

  2. Referee: [Higher-dimensional black holes] Higher-dimensional black holes section: while a richer mode spectrum is reported, the horizon ingoing / infinity outgoing boundary conditions that generate the complex poles remain unchanged. It is therefore unclear how the additional modes remove the time-asymmetry that forces exponentially growing incoming signals, leaving the central claim of total absorption vulnerable to the same realizability objection.

    Authors: We concur that the horizon-ingoing and infinity-outgoing boundary conditions are identical in higher dimensions, so the underlying time-asymmetry is not removed. The richer spectrum of complex poles nevertheless supplies additional degrees of freedom for signal design. In the revised section we now state explicitly that the realizability challenge persists while noting that the larger set of modes can facilitate more flexible, approximately causal waveforms and multi-mode absorption scenarios. This clarification preserves the original observation about the mode structure without overstating its effect on the time-domain issue. revision: partial

Circularity Check

0 steps flagged

Derivation of complete absorption via tailored signals rests on independent resonance construction without self-referential reduction.

full rationale

The paper presents a mathematical construction in which time-dependent modulations of incoming waves are chosen to excite complex-plane resonances (virtual absorption modes), resulting in total absorption during scattering. This relies on standard quasinormal-mode calculations with ingoing horizon and outgoing infinity boundary conditions, which are computed independently of the specific tailored waveform. No step defines the absorption outcome in terms of the input signal itself, renames a fitted quantity as a prediction, or reduces the central result to a self-citation chain. The derivation chain remains self-contained against external benchmarks of linear perturbation theory.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 1 invented entities

The claim rests on the existence of complex-plane resonances that can be driven to total absorption by external modulation, plus standard assumptions of linear perturbation theory around black-hole backgrounds.

axioms (1)
  • domain assumption Linearized wave equations on black-hole spacetimes admit resonances in the complex frequency plane that can be excited by external driving.
    Invoked to justify the existence of virtual absorption modes.
invented entities (1)
  • virtual absorption modes (total transmission modes) no independent evidence
    purpose: Modes that enable complete absorption during the scattering process and later relaxation.
    Newly emphasized class of solutions whose structure is richer in higher dimensions.

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Total transmission modes in draining bathtub model with vorticity

    gr-qc 2026-05 unverdicted novelty 4.0

    Numerical spectra of total transmission modes in the draining bathtub model with vorticity can have positive or negative imaginary parts depending on parameters, with higher overtones exhibiting pronounced spectral mobility.

Reference graph

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