The DESI Dark Energy Tension as a Boundary Projection Effect

Recent data from the Dark Energy Spectroscopic Instrument sharpen the late time tension with a strictly constant cosmological term when the expansion history is written in standard bulk variables. In the present framework, the invariant quantity governing cosmic acceleration is not an effective bulk dark energy density, but a horizon normalized geometric relation between the cosmological constant and the horizon scale. This relation fixes the dimensionless combination Lambda times the squared horizon radius and implies a dark energy fraction equal to pi cubed divided by forty five.

When this fixed boundary relation is rewritten in volumetric form using the relation between the horizon radius and the Hubble parameter, it produces an effective bulk equation of state for dark energy. In this projected description the present day equation of state is w0 approximately minus 0.689, and the effective evolution parameter is wa approximately 0.643. These values arise kinematically from the horizon normalization and do not require phantom fields, quintessence potentials, or additional dark sector degrees of freedom.

The DESI tension is therefore interpreted not as evidence for a new dynamical dark energy fluid, but as the projection of a fixed horizon constraint into bulk cosmological variables. Late time cosmology is governed by boundary geometry, while the apparent evolution of the dark energy sector is the volumetric image of a fixed geometric relation.