In recent years, high-precision x-ray polarimeters have become a key method for the investigation of fundamental physical questions from solid-state physics to quantum optics. Here, we report on verification polarization purity better than $8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ at an free-electron laser, which implies suppression incoming photons noise level in crossed pol...

There is a locally compact Hausdorff space which is linearly Lindelöf and not Lindelöf. This answers a question of Arhangel’skii and Buzyakova.