Generalized scale factor duality symmetry in symmetric teleparallel scalar–tensor FLRW cosmology

We review the Gasperini–Veneziano scale factor duality symmetry for the dilaton field in scalar–tensor theory and its extension in teleparallelism. Within the framework of symmetric teleparallel scalar–tensor theory, we consider a spatially flat Friedmann–Lemaître–Robertson–Walker metric cosmology. For the three possible connections, we write the corresponding point-like Lagrangians for the gravitational field equations, and we construct discrete transformations which generalize the Gasperini–Veneziano scale factor duality symmetry. The discrete transformations depend on the parameter which defines the coupling between the scalar field and the nonmetricity scalar. The Gasperini–Veneziano duality symmetry is recovered for a specific limit of this free parameter. Furthermore, we derive the conservation laws for the classical field equations for these models, and we present the origin of the discrete transformations. Finally, we discuss the integrability properties of the model, and exact solutions are determined.