Gauge fields induced by curved spacetime

I found an extended duality (triality) between Dirac fermions in periodic spacetime metrics, nonrelativistic fermions in gauge fields (e.g., Harper-Hofstadter model), and in periodic scalar fields on a lattice (e.g., Aubry-Andr\'e model). This indicates an unexpected equivalence between spacetime metrics, gauge fields, and scalar fields on the lattice, which are understood as different physical representations of the same mathematical object, the quantum group $\mathcal{U}_q(\mathfrak{sl}_2)$. This quantum group is generated by the exponentiation of two canonical conjugate operators, namely a linear combination of position and momentum (periodic spacetime metrics), the two components of the gauge-invariant momentum (gauge fields), and position and momentum (periodic scalar fields). Hence, on a lattice, Dirac fermions in a periodic spacetime metric are equivalent to nonrelativistic fermions in a periodic scalar field after a proper canonical transformation. The three lattice Hamiltonians (periodic spacetime metric, Harper-Hofstadter, and Aubry-Andr\'e) share the same properties, namely fractal phase diagrams, self-similarity, $S$-duality, topological invariants, flat bands, and topologically quantized current in the incommensurate regimes. In essence, this work unveils an unexpected link between gravity and gauge fields, opens new avenues for studying analog gravity, e.g., the Unruh effect and universe expansions/contractions, suggests the existence of an $S$-duality of spacetime curvatures, and hints at novel pathways to quantized gravity theories.