Science China Physics, Mechanics & Astronomy最新文献

There is a possibility of interaction between dark energy and dark matter, and it may undergo a sign change during the evolution of the universe. In this paper, we utilize the latest DESI baryon acoustic oscillation data, along with type Ia supernova data from DES and cosmic microwave background data from Planck and ACT, to constrain models of sign-changeable interaction. From our analysis, we observe that the coupling β(z) crosses the non-interacting line β(z) = 0 and changes sign from positive to negative during cosmic evolution. Specifically, we find that the existence of sign-changeable interaction in the model with Q = β(a)H₀ρ_de is supported by the current data at the 4.1σ level. Our findings indicate that the energy transfer is from dark matter to dark energy when dark matter dominates the universe, and from dark energy to dark matter when dark energy dominates, for the models with Q ∝ ρ_de. Furthermore, Bayesian evidence suggests that the Q ∝ ρ_de models are moderately preferred over the ACDM model. The overall outcomes of this study clearly indicate that, based on current observational data, the sign-changeable interacting dark energy models are quite compelling and merit further attention.

Trilayer Ruddlesden-Popper phase La₄Ni₃O₁₀ has been observed with T_c of ∼30 K at high pressure in a recent experiment, which further expanded the family of nickelate superconductors. In this study, we explored the effects of electronic correlations in La₄Ni₃O₁₀ using density functional theory plus dynamical mean-field theory at ambient and high pressures. Our derived spectral functions and Fermi surface of the ambient pressure phase are nicely consistent with the experimental results by angle-resolved photoemission spectroscopy, which emphasized the importance of electronic correlations in La₄Ni₃O₁₀. We also found the electronic correlations in pressurized La₄Ni₃O₁₀ are both orbital-dependent and layer-dependent due to the presence of Hund’s rule coupling. There is a competition between the Hund’s rule coupling and the crystal-field splitting, and therefore, the Ni–O layers with weaker crystal-field splitting energy would have stronger electronic correlations.

Galaxy clustering is an important probe in the upcoming China Space Station Telescope (CSST) survey to understand the structure growth and reveal the nature of the dark sector. However, it is a long-term challenge to model this biased tracer and connect the observable to the underlying physics. In this work, we present a hybrid Lagrangian bias expansion emulator, combining the Lagrangian bias expansion and the accurate dynamical evolution from N-body simulation, to predict the power spectrum of the biased tracer in real space. We employ the Kun simulation suite to construct the emulator, emulating across the space of 8 cosmological parameters including dynamic dark energy w₀, w_a, and total neutrino mass Σ m_v. The sample variance due to the finite simulation box is further reduced using the Zel’dovich variance control, and it enables the precise measurement of the Lagrangian basis spectra up to the quadratic order. The emulation of basis spectra realizes 1% level accuracy, covering wavelength k ⩽ 1 Mpc⁻¹ h and redshift 0 ⩽ z ⩽ 3 up to the quadratic order field. To validate the emulator, we perform a joint fit to the halo auto power spectrum and the halo-matter cross power spectrum measured from 46 independent simulations. Depending on the choice of counterterm, the joint fit is unbiased up to k_max ≃ 0.7 Mpc⁻¹ h within 1–2 percent accuracy, for all the redshift and halo mass samples. As part of the CSST cosmological emulator series, this emulator is expected to provide accurate theoretical predictions for the galaxy power spectrum in upcoming CSST survey.