查看更多>>摘要：Several Pulsar Timing Array(PTA)Collaborations have recently provided strong evidence for a nHz Stochastic Gravitational-Wave Background(SGWB).Here we investigate the implications of a first-order phase transition occurring within the early Universe's dark quantum chromodynamics epoch,specifically within the framework of the mirror twin Higgs dark sector model.Our analysis indicates a distinguishable SGWB signal originating from this phase transition,which can explain the measurements obtained by PTAs.Remarkably,a significant portion of the parameter space for the SGWB signal also effectively resolves the existing tensions in both the H0 and S8 measurements in Cosmology.This intrigu-ing correlation suggests a possible common origin of these three phenomena for 0.2＜ΔNeff＜0.5,where the mirror dark matter component constitutes less than 30％of the total dark matter abundance.Next-generation CMB experiments such as CMB-S4 can test this parameter region.
查看更多>>摘要：The realization of spin-orbit-coupled ultracold gases has driven a wide range of research and is typically based on the rotating wave approximation(RWA).By neglecting the counter-rotating terms,RWA char-acterizes a single near-resonant spin-orbit(SO)coupling in a two-level system.Here,we propose and experimentally realize a new scheme for achieving a pair of two-dimensional(2D)SO couplings for ultra-cold fermions beyond RWA.This work not only realizes the first anomalous Floquet topological Fermi gas beyond RWA,but also significantly improves the lifetime of the 2D-SO-coupled Fermi gas.Based on pump-probe quench measurements,we observe a deterministic phase relation between two sets of SO couplings,which is characteristic of our beyond-RWA scheme and enables the two SO couplings to be simultaneously tuned to the optimum 2D configurations.We observe intriguing band topology by measuring two-ring band-inversion surfaces,quantitatively consistent with a Floquet topological Fermi gas in the regime of high Chern numbers.Our study can open an avenue to explore exotic SO phy-sics and anomalous topological states based on long-lived SO-coupled ultracold fermions.
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