摘要
本文总结了极强磁场下量子色动力学(Quantum Chromodynamics,QCD)相变的研究现状和许多新进展,包括格点QCD和有效手征模型的计算结果。涉及的QCD相如下:手征对称性破缺、手征对称性恢复、非均匀手征相、π0凝聚、π超流、ρ凝聚以及色超导。除了强磁场B外,这些相的实现和相互转化还要同时考虑其他效应的共同作用,比如温度T、强电场E、各种化学势μ或转动角速度Ω等。与之对应,介绍一些由磁场和这些物理参量共同张成的相图:T-B相图、E-B相图、μB-B相图、μI-B相图以及Ω-B相图,并阐述相变背后的物理机制。
Several experiments are being conducted at heavy-ion colliders around the world to determine the location of the proposed critical end point of quantum chromodynamics(QCD)in the T-μB phase diagram.As the presence of a very strong magnetic field is relevant to peripheral heavy-ion collisions,magnetars,and the early Universe,it is important to investigate the effect of a high magnetic field strength on QCD phase diagrams.We summarize the recent status and new developments in studies investigating QCD phase transitions under an extremely strong magnetic field.By doing so,we believe that this work will promote both theoretical and experimental research in this field.The T-B phase diagrams are produced by Lattice QCD simulations.Other phase diagrams(E-B,μB-B,μI-B,andΩ-B)are mainly studied by using the chiral effective Nambu Jona-Lasinio model.A rotating magnetic field is adopted for the study of color superconductivity.The Ginzburg-Landau approximation is used to studyπ-superfluidity andρ-superconductivity in a very strong magnetic field.Physical effects,besides a magnetic field B,can also be measured when sketching a QCD phase diagram,such as temperature T,strong electric field E,chemical potentialsμ,and rotational angular velocityΩ.We present five QCD phase diagrams:T-B,E-B,μB-B,μI-B,andΩ-B.The following phases are present in many(if not all)of the five QCD phase diagrams:chiral symmetry breaking,chiral symmetry restoration,inhomogeneous chiral phase,π0-condensation,π-superfluidity,ρ-superconductivity,and color superconductivity.The running of the coupling constant with magnetic field is consistent with the decrease of the pseudo-critical deconfinement temperature,providing a natural explanation for the inverse magnetic catalysis effect.We also found that a chiral anomaly induces pseudoscalar condensation in a parallel electromagnetic field,and that there appears to be a chiral-symmetry restoration phase in the E-B phase diagram.Without consideration of confinement,color superconductivity is typically favored for large baryon chemical potential;however,chiral density wave is also possible in the large B and relatively smallμB region of the phase diagram.In an external magnetic field,theπ-superfluid with finite isospin chemical potential acts similarly to a Type-II superconductor with finite electric chemical potential.Bothπ-superfluidity andρ-superconductivity are possible in a parallel magnetic field and rotation,but the latter is more favored for largerΩparticles.
作者
曹高清
CAO Gaoqing(School of Physics and Astronomy,Sun Yat-sen University,Zhuhai 519088,China)
出处
《核技术》
CAS
CSCD
北大核心
2023年第4期32-46,共15页
Nuclear Techniques
基金
国家自然科学基金(No.11805290)资助。
关键词
极强磁场
QCD相变
相图
反磁催化
π凝聚
ρ超导
Very strong magnetic field
QCD phase transition
Phase diagram
Inverse magnetic catalysis
πcondensation
ρsuperconductivity
