Observation of Universal Expansion Anisotropy from Cold Atoms to Hot Quark-Gluon Plasma

Fuente: arXiv
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Autori principali: Li, Ke, Song, Hong-Fang, Xu, Hao-Jie, Sun, Yu-Liang, Wang, Fuqiang
Natura: Preprint
Pubblicazione: 2024
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author Li, Ke
Song, Hong-Fang
Xu, Hao-Jie
Sun, Yu-Liang
Wang, Fuqiang
author_facet Li, Ke
Song, Hong-Fang
Xu, Hao-Jie
Sun, Yu-Liang
Wang, Fuqiang
contents Azimuthal anisotropy has been ubiquitously observed in high-energy proton-proton, proton-nucleus, and nucleus-nucleus (heavy-ion) collisions, shaking the early belief that those anisotropies require an intense phase of multiple interactions between the created particles. This work reports a study of anisotropic expansion of cold $^{6}$Li Fermi gases, initially trapped in an anisotropic potential, as a function of the interaction strength that can be readily tuned by an external magnetic field. It is found that the expansion anisotropy builds up quickly at small interaction strength, without the need of a large amount of interactions. An unexpected and quantitative universal scaling of the expansion anisotropy is observed for the first time between cold atom and heavy-ion systems as a function of the number of collisions per particle or opacity ($n_{\rm coll}$), despite their vast differences in scale and physics. The expansion isotropy in both the cold atom gases and heavy-ion collisions increases smoothly and shows no sign of saturation in the observed opacity range, with an approximate power-law dependence of $\sqrt{n_{\rm coll}}$, characteristic of random walks. This universality potentially unifies a variety of vastly different physical systems, from weakly interacting dilute gases to the strongly interacting quark-gluon plasma of the early universe.
format Preprint
id arxiv_https___arxiv_org_abs_2405_02847
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Observation of Universal Expansion Anisotropy from Cold Atoms to Hot Quark-Gluon Plasma
Li, Ke
Song, Hong-Fang
Xu, Hao-Jie
Sun, Yu-Liang
Wang, Fuqiang
Quantum Gases
Nuclear Experiment
Nuclear Theory
Azimuthal anisotropy has been ubiquitously observed in high-energy proton-proton, proton-nucleus, and nucleus-nucleus (heavy-ion) collisions, shaking the early belief that those anisotropies require an intense phase of multiple interactions between the created particles. This work reports a study of anisotropic expansion of cold $^{6}$Li Fermi gases, initially trapped in an anisotropic potential, as a function of the interaction strength that can be readily tuned by an external magnetic field. It is found that the expansion anisotropy builds up quickly at small interaction strength, without the need of a large amount of interactions. An unexpected and quantitative universal scaling of the expansion anisotropy is observed for the first time between cold atom and heavy-ion systems as a function of the number of collisions per particle or opacity ($n_{\rm coll}$), despite their vast differences in scale and physics. The expansion isotropy in both the cold atom gases and heavy-ion collisions increases smoothly and shows no sign of saturation in the observed opacity range, with an approximate power-law dependence of $\sqrt{n_{\rm coll}}$, characteristic of random walks. This universality potentially unifies a variety of vastly different physical systems, from weakly interacting dilute gases to the strongly interacting quark-gluon plasma of the early universe.
title Observation of Universal Expansion Anisotropy from Cold Atoms to Hot Quark-Gluon Plasma
topic Quantum Gases
Nuclear Experiment
Nuclear Theory
url https://arxiv.org/abs/2405.02847