Speaker
Описание
Abstract
Astonishingly, it was discovered that distant Type Ia supernovae (SN Ia) were accelerating away at an increasing pace. This led to the great discovery of late-time cosmic acceleration and brought us the concept of dark energy, responsible for such a phenomenon. However, the underlying nature remains mysterious. Theoretically, modified gravity can be a framework to provide an alternative explanation for the the existence of dark energy. In this talk, we explore the theoretical perspectives of understanding the late-time cosmic acceleration. In particular, we will discuss the effective field theory of dark energy and modified gravity. Using the Dark Energy Spectroscopic Instrument (DESI) data released in 2025 as well as other observational data, we are able to reconstruct the background evolution and find that the reconstructed dark-energy equation-of-state (EoS) parameter w(z) exhibits the so-called quintom behavior, crossing -1 from phantom to quintessence regime as the universe expands. We reconstruct the corresponding actions for f(R), f(T), and f(Q) gravity, respectively. We conclude that, certain modified gravity such as metric-affine gravity can exhibit the quintom dynamics and fit the recent DESI data efficiently, and for all cases the quadratic deviation from the ΛCDM scenario is mildly favored.
Links
https://arxiv.org/abs/2404.19437 https://arxiv.org/abs/2501.18336 https://arxiv.org/abs/2504.06784 https://arxiv.org/abs/2505.24732