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Dark energy has attracted renewed attention since DESI reported a possible dynamical behavior crossing the cosmological constant boundary, favoring the (w0,wa) parametrization over a cosmological constant at more than 3\sigma. This apparent evolution is a manifestation of some discrepancies between DESI BAO, Planck CMB and supernovae measurements. An independent probe from DESI and SN is therefore crucial to understand whether the preference for evolving dark energy comes from systematics in the data or from new physics.

In this talk, I will present our efforts towards this question using large-scale structure data. I will begin by introducing the Effective Field Theory of Large-Scale Structure (EFTofLSS), which enables a consistent one-loop treatment of the bispectrum to enhance cosmological constraints. Incorporating the BOSS DR12 bispectrum improves the (w0, wa) constraints by about 30% and yields more than 2.8\sigma indication of evolving dark energy. I will then discuss the auto- and cross-correlation between the DESI Legacy Survey and CMB lensing, a probe of late-time universe that enables a supernova-independent test of dark-energy evolution. This combination provides a 2.3\sigma indication of evolving dark energy without relying on DESI BAO or supernova data. Finally, I will present updated constraints on modified gravity parameters, which remain consistent with General Relativity at the 2\sigma level.

BIO

Zhiyu Lu is a Ph.D. candidate in cosmology in the Cospa Group at the University of Science and Technology of China. His research focuses on developing and applying the Effective Field Theory of Large-Scale Structure (EFTofLSS) to probe dynamical dark energy, modified gravity, and primordial non-Gaussianity. By building unified one-loop analyses of the power spectrum, bispectrum, and trispectrum, he aims to extract maximal information from upcoming surveys and place stringent constraints on both late-time and early-time of the Universe.

Host: Cheng Zhao