Hydrodynamic and Non-hydrodynamic Excitations in Kinetic Theory -- A Numerical Analysis in Scalar Field Theory
Stephan Ochsenfeld, Sören Schlichting
备注：
30 pages and 8 figures. v2 changes: Added a more nuanced discussion about hydrodynamization in introduction. Clarified the potential differences between the QFT scalar ϕ^4 theory and kinetic theory derived from it. Added some additional discussion of a hydrodynamic breakdown scale k_c to the conclusion of the paper. Fixed some typos. v3 changes: added code to source files
Viscous hydrodynamics serves as a successful mesoscopic description of the Quark-Gluon Plasma produced in relativistic heavy-ion collisions. In order to investigate, how such an effective description emerges from the underlying microscopic dynamics we calculate the hydrodynamic and non-hydrodynamic modes of linear response in the sound channel from a first-principle calculation in kinetic theory. We do this with a new approach wherein we discretize the collision kernel to directly calculate eigenvalues and eigenmodes of the evolution operator. This allows us to study the Green's functions at any point in the complex frequency space. Our study focuses on scalar theory with quartic interaction and we find that the analytic structure of Green's functions in the complex plane is far more complicated than just poles or cuts which is a first step towards an equivalent study in QCD kinetic theory.
Hydrodynamics without Boost-Invariance from Kinetic Theory: From Perfect Fluids to Active Flocks
National Institute of Physics, University of the Philippines（菲律宾大学物理研究所）；Niels Bohr International Academy, The Niels Bohr Institute, University of Copenhagen（尼尔斯·玻尔国际学院，尼尔斯·玻尔研究所，哥本哈根大学）；Nordita, KTH Royal Institute of Technology and Stockholm University（北欧理论物理中心，皇家理工学院和斯德哥尔摩大学）；Instituut-Lorentz for Theoretical Physics, Leiden University（莱顿大学洛伦兹理论物理研究所）
École polytechnique, Centre National de la Recherche Scientifique – Unité Mixte de Recherche 7644, Institut Polytechnique de Paris（巴黎综合理工学院，法国国家科学研究中心第7644联合研究单位，巴黎理工学院）；Université Libre de Bruxelles and International Solvay Institutes（布鲁塞尔自由大学和国际索尔维研究所）；Université de Mons（蒙斯大学）
