Quantum gravity meets DESI: dynamical dark energy in light of the trans-Planckian censorship conjecture
Chunyu Li, Junkai Wang, Dongdong Zhang, Emmanuel N. Saridakis, Yi-Fu Cai
Abstract
Abstract Recent DESI DR2 observations indicate that dark energy has crossed from phantom to quintessence regime, a behavior known as the quintom-B realization. In this work we constrain dynamical dark energy and modified gravity using the swampland Trans-Planckian Censorship Conjecture (TCC), which forbids eternal acceleration since in this case any trans-Planckian quantum fluctuation would eventually stretch beyond the Hubble radius, breaking the applicability of any effective field theory and cosmological techniques. By combining DESI DR2 data with the TCC criterion, we impose tight constraints on the dark energy equation of state and its parameter space in scenarios such as the CPL, BA, JBP, EXP and LOG parameterizations, significantly constraining the quintom-A behavior. In addition, we extend the application of TCC to modified gravity theories, demonstrating that TCC is also very powerful to constrain or exclude f ( T ), f ( Q ) gravities, and necessities to consider infrared modifications of Einstein gravity. Our findings imply that viable dynamical dark energy scenarios must asymptotically transit to deceleration, shedding light on new physics consistent with both cosmological observations and quantum gravity principles.