Cosmological constraints from UV/IR mixing

Holography and entropy bounds suggest that the ultraviolet (UV) and infrared (IR) cutoffs of gravitational effective theories are related to one another as a form of UV/IR mixing. Motivated by this, we derive a bound on the allowed scalar field range in theories with cosmic horizons. We show how this bound challenges several inflationary scenarios, such as $α$-attractors and modular-invariant inflation. Besides, we find a relation between the number of extra spatial dimensions and the tensor-to-scalar ratio.