Alexander Zhuk (Odessa I.I.Mechnikov National University, Ukraine and Center for Advanced Systems Understanding (CASUS), Görlitz, Germany)

Dynamical dark energy with AdS-dS and dS-dS transitions: Alleviation of the H0 tension

The problem of cosmological tensions is one of the hottest problems in modern cosmology. The most significant tension is the 5 deviation between the Hubble constant measured by the local distance ladder (i.e., the SHOES results) and the cosmic microwave background. The ΛsCDM model is one of the most successful since it simultaneously addresses the major cosmological tensions. This phenomenological model suggests that at the late stage of the evolution of the Universe, the cosmological constant almost instantaneously changes its sign from negative to positive (i.e., the model undergoes a rapid Anti-de Sitter to de Sitter transition). In my talk I will present the physical justification of this model at a fundamental level, starting with a physical action. The main feature of this model is that the dynamical dark energy is modeled by a phantom scalar field with a specific form of potential. The numerical integration of the equations of motion is performed in such a way that both the CMB data and the results of the SHOES are satisfied, which significantly reduces the problem of cosmological tensions. A detailed analysis of the dynamical behavior of parameters of the model demonstrates that all curves are continuous and the weak energy condition is satisfied.