摘要：Astonishingly, human beings 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, but the underlying nature remains mysterious. Theoretically, modified gravity can be a framework to provide an alternative explanation for the existence of dark energy. In this talk, we will go further into the effective field theory of dark energy in light of the latest cosmological observations. In particular, using the latest Dark Energy Spectroscopic Instrument (DESI) data combined with other observations, we reconstructed the cosmological background evolution and find that the reconstructed dark-energy equation-of-state (EoS) parameter w(z) exhibits the so-called quintom-B behavior, crossing−1 from phantom to quintessence regime as the universe expands. In particular, we reconstruct the corresponding actions for f(R), f(T), and f(Q) gravity, respectively. Our analyses indicate that, certain modified gravity such as metric-affine gravity could 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.