Event Horizons, Spacetime Geometry, and the Limits of Integrated Consciousness

Extended systems are often treated as unified whenever internal causal interactions are sufficiently dense and recurrent over a characteristic timescale (Tononi, 2004; Baars, 1988; Friston, 2010). In relativistic spacetimes with one-way causal boundaries (such as black-hole event horizons, cosmolog- ical horizons, and Rindler wedges) and strong curvature, this background assumption can fail: closed causal loops that sustain macroscopic informational unity predicates can be obstructed without any local disruption of microphysical evolution (Hawking and Ellis, 1973; Wald, 1984). This paper intro- duces the Reciprocal Coherence Kernel KT (t), defined as the inclusion-minimal, strongly connected operational subgraph that sustains a unified perspective according to a theory-relative functional predicate FT . Kernel persistence is analysed using a relativistically explicit condition: the effective causal diameter Λ(KT (t)) must remain less than or equal to a theory–and–model-specific coherence window τT,m, measured in proper time. When Λ(KT (t)) > τT,m, or when a strict one-way boundary intersects the kernel, unity (as defined by the theory’s own predicate) fails by coherence timeout, an operationally distinct failure mode from mechanical destruction. A theory-relative taxonomy of geometry-sensitive versus geometry-robust unity predicates is developed. The framework is applied to horizon-straddling implementations, distributed systems, and selected fault-tolerant architectures (Nielsen and Chuang, 2010). The project is explicitly non-causal. It offers a compatibility analysis over theory-indexed model families, not a causal explanation of consciousness. The contribution lies in philosophy of science: diagnosing hidden structural commitments in integration-based theories and exposing geometric constraints on extended subjects in relativistic spacetimes (Woodward, 2003; Ladyman and Ross, 2007)