The Bühring Interior Metric Deformation Model: A Phenomenological Regular Black Hole Interior from Radial Causal Structure

We propose a phenomenological regular black hole interior obtained by introducing a radial causal deformation of the Schwarzschild metric. Instead of modifying the mass function, the model introduces a dimensionless radial deformation factor β(r) that alters the interior light-cone structure while preserving the exact Schwarzschild exterior. This construction removes the central singularity and replaces it with a finite, regular core while maintaining continuity at the event horizon. The resulting spacetime remains static and spherically symmetric and satisfies regularity conditions at r → 0. The model provides an alternative to traditional regular black hole constructions and offers a geometrically motivated interpretation in which the interior structure is governed by a deformation of radial causal propagation. This leads to finite curvature invariants and a smooth interior geometry without introducing an explicit exotic matter profile.