DESI and Dynamical Dark Energy from Extended Pre-geometric Gravity

We consider the simplest quadratic extension of MacDowell-Mansouri pre-geometric gravity preserving the topological pre-volume form symmetry. After symmetry breaking, it becomes $(\mathrm{L}\mathrm{o}\mathrm{v}\mathrm{e}\mathrm{l}\mathrm{o}\mathrm{c}\mathrm{k}{)}^2$ gravity, dual to a Galileon-like Horndeski scalar-tensor theory. The gravitational Higgs mechanism forces the Gauss-Bonnet coupling to be inversely proportional to the bare cosmological constant. The quadratic correction renders the gravitational $\theta$-angle dynamical in the form of a gravi-axion, whose effective mass sets the dark energy scale, thus naturally realizing a dynamical dark energy. The model fits DESI’s BAO+FS data exceptionally well (${\chi }_{\mathrm{r}\mathrm{e}\mathrm{d}}^2=1.394$), deviating from $\mathrm{\Lambda }\mathrm{C}\mathrm{D}\mathrm{M}$ by only a few percent in the gravitational slip parameter $\gamma (z)$ with stable tensor perturbations. This analysis establishes a concrete, testable bridge between pre-geometric gravity and cosmic acceleration.