The Horizon as a Channel Boundary
A medium-based view of an “event horizon” as the operational limit of a causal channel. This is a methodological note: it does not start from a specific metric, but from the accessibility of measurable correlation.
A horizon is not a geometric ban — it is a boundary between transmission regimes.
A causal channel instead of an a priori geometry
In a medium-based picture, causality is implemented not by an abstract geometry and not by an a priori limiting speed, but by robust physical carriers that can transport a measurable correlation between events.
Therefore, it is natural to start the horizon analysis not from the metric and not from the speed of light, but from a practical question: does the causal channel work — i.e., do stable transmission carriers form, and does an operationally recoverable correlation persist?
Two meanings of c
It is useful to separate two meanings of the constant c. The first is structural: a scale used for constructing coordinates, synchronization, and local causality. It fixes the form of transformations and ensures the consistency of local descriptions.
The second is operational: the actual speed and robustness of correlation transfer in a specific physical realization. In a medium-based approach, the information transfer speed is an effective property of the medium and may depend on its state.
The carrier of causality
Causality is realized through a carrier — a minimal local excitation of the medium that can be produced, detected, and maintains operational identity across the transmission scale. Such a carrier need not be a “particle” in the conventional sense.
Quasiparticles and modes arise only in regimes where the medium is sufficiently homogeneous and linear. More generally, the carrier of causality may be a local defect, an impulse chain, or a collective excitation.
Three transmission regimes
The key parameter is the carrier’s stability. Depending on the medium state, three regimes can be distinguished:
- Coherent: the excitation preserves shape and phase; correlation is transferred and can be recovered.
- Dispersive: the signal shape distorts and phase is partially lost; some information remains accessible.
- Decoherent: the excitation degrades faster than a robust transmission can form; correlation falls to the noise level.
The horizon as a regime transition
In this description, an event horizon corresponds not to a prohibition and not to a singularity, but to a transition between regimes — a boundary beyond which stable carriers of reverse causal feedback no longer form. This is a dynamic, channel-based criterion, not a geometric one.
No extreme medium parameters are required: it is sufficient to lose transmission coherence, increase dispersion, or amplify local fluctuations so that the impulse chain collapses.
Blackness, noise, and “radiation”
The observed “blackness” of the horizon is a property of the observation channel rather than the object itself. If no coherent return channel exists, external probing does not receive a recoverable response. For an observer, this is indistinguishable from perfect absorption, even if internal redistribution of energy and momentum continues.
Noise and vortex-like regimes are a background feature of the medium. Yet near the boundary between transmission regimes, the symmetry of fluctuation compensation breaks, and a portion of the noise spectrum becomes directionally accessible to the external observer — appearing as a quasi-thermal background.
Its “temperature” is an effective spectral parameter set by filtering and channel degradation, not necessarily a signature of local thermodynamic equilibrium. Alongside this incoherent background, coherent unloading channels may exist (e.g., vortical structures and jets).
Information as operationality
Operationally, information in physics is a measurable correlation accessible via a physical channel.
In a regime where stable carriers of reverse feedback do not exist, information need not dynamically disappear. It loses operationality: it stops being addressable and recoverable, redistributing across collective degrees of freedom of the medium.
In this sense, a horizon is not a boundary of reality, but a boundary of applicability for an operational description.
In brief
- horizon — the limit of channel viability, not a geometric ban;
- blackness — absence of recoverable reverse correlation;
- radiation — noise manifestation near the stability threshold;
- “information loss” — loss of operationality.