SU(N) symmetry can emerge in a quantum system with N single-particle spin states when spin is decoupled from inter-particle interactions. Here, we report a spectroscopic observation of SU(N ≤ 10) symmetry in 87Sr taking advantage of the high measurement precision offered by an ultra-stable laser. By encoding the electronic orbital degree of freedom in two clock states, while keeping the system open to as many as 10 nuclear spin sublevels, we probe the non-equilibrium two-orbital SU(N) magnetism via Ramsey spectroscopy of atoms confined in an array of two-dimensional optical traps. We study the spin-orbital quantum dynamics and determine the relevant interaction parameters. This work lays the groundwork for using alkaline-earth atoms as test-beds for important orbital models.
Seven particles captured by the Stardust Interstellar Dust Collector and returned to Earth for laboratory analysis have features consistent with an origin in the contemporary interstellar dust stream. More than 50 spacecraft debris particles were also identified. The interstellar dust candidates are readily distinguished from debris impacts on the basis of elemental composition and/or impact trajectory. The seven candidate interstellar particles are diverse in elemental composition, crystal structure, and size. The presence of crystalline grains and multiple iron-bearing phases, including sulfide, in some particles indicates that individual interstellar particles diverge from any one representative model of interstellar dust inferred from astronomical observations and theory.
In his book Abbey’s Road ,Edward Abbey wrote (h/t:abbeyweb.net): “I am […] descended from an endless line of dark-complected, lug-eared, beetle-browed, insolent barbarian peasants, a line reaching back to the dark forests of central Europe and the alpine caves of my Neanderthal primogenitors.”