The article like nearly every physical article has its preprint available on the arxiv. https://arxiv.org/abs/1603.07224 https://arxiv.org/abs/1603.07224 note

The article like nearly every physical article has its preprint available on the arxiv. https://arxiv.org/abs/1603.07224 https://arxiv.org/abs/1603.07224 note: "on the arxiv" and not "on arxiv". The name puns on x => greek letter chi.