A Minimal Boundary Interpretation of Large-Scale Cosmological Anomalies

Large-scale cosmological anomalies persist across independent datasets and physical domains, including CMB temperature and polarization, low-ℓ alignments, hemispherical asymmetry, radio number-count dipoles, galaxy spin chirality, bulk flows, void thermodynamics, and directional variation in the Hubble parameter. Although often treated as unrelated statistical outliers, these anomalies exhibit directional convergence, cross-domain coherence, and scale consistency that are highly unlikely under isotropic LambdaCDM initial conditions. This paper adopts a conservative, data-first analysis and shows that no known internal LambdaCDM mechanism can simultaneously account for these correlated features. The anomalies are instead explained by a single minimal modification to the primordial boundary conditions: an anisotropic boundary condition or primordial modulation field. The most general linear boundary tensor consistent with symmetry is written as P⏛⏜ = α n⏛ n⏜ + β ε⏛⏜⏚ n^λ + γ (t) S⏛⏜, with α introducing directionality, β producing parity-odd signatures, and γ (t) generating dynamic anisotropic stress. This minimal boundary influence preserves General Relativity, maintains the success of LambdaCDM across small- and intermediate-scale observations, and modifies only the earliest definable hypersurface. Each boundary parameter is mapped to the anomalies it explains, and a suite of falsifiable predictions is derived for CMB-S4, LiteBIRD, SKA, LSST, Euclid, and DESI. The analysis isolates the empirical structure motivating an anisotropic boundary condition; a companion work will address the physical microstructure capable of generating such a boundary.