量子色动力学在有限温度密度区间的相结构

本文综述量子色动力学在有限温度密度区间的相结构,包括高密条件下的色超导态和在高温条件下相对论重离子碰撞实验中产生的强耦合夸克-胶子等离子体。我们简要地介绍在相对论重离子碰撞实验中发现强耦合夸克-胶子等离子体的历史,并且讨论用体粘滞系数与熵的比值确定QCD临界点的可能性。对于在高密区域的相结构,我们着重讨论错位配对情况下的非标准色超导态,解释无能隙色超导态的色磁不稳定性、Sarma不稳定性和Higgs不稳定性.     

一种新的物质形态——夸克胶子等离子体

进入21世纪以来,随着美国Brookhaven国家实验室的相对论重离子对撞机和欧洲核子中心的大型强子对撞机的相继运行,对于物质深层次状态的认识达到了前所未有的高度。特别是对于夸克胶子等离子体这种新的物质形态的研究得到蓬勃发展,取得很多成就。文章主要介绍：(1)强相互作用和量子色动力学的相结构;(2)夸克胶子等离子体的物理性质;(3)夸克胶子等离子体在重离子碰撞实验中的信号。     

柱形夸克胶子等离子体的2π干涉学检测

在2п干涉学中,对不同的п源2п,关联函数可以是不同的. 如果在相对论重离子碰撞中出现柱形夸克胶子等离子体,п介子将从柱形夸克胶子等离子体表面发射,此时2п关联函数将出现一种特殊的振荡行为.这种振荡行为可以用来探明夸克胶子等离子体的存在性,同时也是相对论重离子碰撞中出现夸克胶子等离子体的一个信号.     

ALICE新内寻迹系统——硅像素探测器

大型重离子对撞机实验（ALICE）是大型强子对撞机（LHC）上唯一致力于研究极端相对论下的原子核碰撞的实验。其目标是研究强相互作用物质在实验室达到的极高能量密度下的物理特性。在极高能量密度下,能够产生一种新的物质形态——夸克-胶子等离子体。宇宙被认为在大爆炸后的最初几百万分之一秒就处于夸克-胶子等离子体状态。     

相对论重离子碰撞中的软探针和硬探针

简要回顾了高能核碰撞中夸克胶子等离子体的软探针和硬探针的一些最新进展,主要内容集中在相对论重离子对撞机和大型强子对撞机实验中各向异性集体流和喷注淬火的理论和唯象研究,对小系统中集体流的来源也做了简要的讨论。对于软探针,讨论了初态三维涨落和碰撞几何各向异性、相对论流体力学演化、末态各向异性集体流以及集体流的涨落、关联和纵向去关联等。通过与实验数据作系统的比较,可以探测重离子碰撞中夸克胶子等离子体的动力演化和各种输运性质。对于硬探针,集中讨论了部分子能量损失和喷注淬火对部分子味道的依赖性、重味夸克在夸克胶子等离子体中的强子化、整体喷注在核介质中的演化以及核介质对喷注的响应等。细致分析相关的观测量,可以帮助我们更全面地了解相对论核碰撞中喷注与核介质的相互作用以及重味粒子的生成。对于小系统,讨论初态和末态效应在解释小系统中轻强子和重味强子的集体流方面的贡献,这有助于我们理解大碰撞系统中集体流的起源成因。     

强相互作用自旋-轨道耦合与夸克-胶子等离子体整体极化

在非对心相对论重离子碰撞中,参与反应的原子核物质系统具有巨大的初始轨道角动量,经过强相互作用的自旋-轨道耦合,这一巨大的轨道角动量可以转化为产生的夸克-胶子等离子体的整体极化.整体极化效应在理论上提出后,首先被美国布鲁克海文国家实验室的相对论重离子对撞机上的STAR实验所证实,激发了人们对相关问题的研究,成为重离子碰撞物理研究的一个新方向——重离子碰撞自旋物理.本文简单回顾了整体极化原始基本思想、理论计算体系与主要结果以及近几年的理论进展.     

胶子非弹性散射过程对夸克胶子等离子体中双轻子产生的影响

双轻子是研究夸克物质的形成和性质的重要探针.本文基于化学平衡化的黏滞性夸克胶子等离子体演化模型,计算了相对论重离子碰撞能量下金-金对心碰撞形成的夸克胶子等离子体中的双轻子产额.在黏滞性计算中加入了胶子非弹性散射过程对黏滞系数的贡献.相较仅考虑夸克和胶子弹性散射的情况,双轻子的产额有较明显的降低.这表明在黏滞系数中加入胶子非弹性散射的贡献使得系统的演化过程加快,演化时间变短.     

在大型强子对撞机上探索物质本源的大型重离子实验

欧洲核子研究中心的大型重离子实验探测器(ALICE),利用2008年开始运行的大型强子对撞机(LHC),将核物质加热到太阳中心温度的几十万倍,研究在高温高密的极端环境下生成的新物质形态(夸克胶子等离子体或夸克物质)的性质.这样的实验有可能从本源上探索:强作用力如何支配物质结构?夸克作为强作用力的基本量子,如何禁闭于质子和中子内部?夸克作为物质的基本组成单元,质量从何而来?文章介绍在大型强子对撞机上探索物质本源的大型重离子实验,内容包括:强作用力与夸克模型、渐进自c由与夸克禁闭、重离子碰撞与夸克物质、LHC上的ALICE实验、连通夸克和宇宙.     

在大型强子对撞机上探索物质本源的大型重离子实验

欧洲核子研究中心的大型重离子实验探测器(ALICE),利用2008年开始运行的大型强子对撞机(LHC),将核物质加热到太阳中心温度的几十万倍,研究在高温高密的极端环境下生成的新物质形态（夸克胶子等离子体或夸克物质）的性质.这样的实验有可能从本源上探索:强作用力如何支配物质结构？夸克作为强作用力的基本量子,如何禁闭于质子和中子内部？夸克作为物质的基本组成单元,质量从何而来？文章介绍了在大型强子对撞机上探索物质本源的大型重离子实验,内容包括：强作用力与夸克模型、渐进自c由与夸克禁闭、重离子碰撞与夸克物质、LHC上的ALICE实验、连通夸克和宇宙.     

欧洲核子研究中心发现新物质形态——夸克胶子等离子体存在的证据

介绍和评述了欧洲核子研究中心（CERN）的相对论重离子碰撞的重要实验结果及其物理解释。碰撞初期形成了高温高密系统。能量密度达到了产生夸克胶子等离子体（QGP）的阈值,低质量双轻子增长、J／ψ反常压低和奇异粒子增长等实验现象可以用形成了QGP来解释。但目前的实验还不足以证明已经产生了QGP。     

Superdense matter

We review recent work on the phase structure of QCD at very high baryon density. We introduce the phenomenon of color superconductivity and discuss the use of weak coupling methods. We study the phase structure as a function of the number of flavors and their masses. We also introduce effective theories that describe low energy excitations at high baryon density. Finally, we comment on the possibility of kaon condensation at very large baryon density.     

Phase transition of the baryon-antibaryon plasma in hot and dense nuclear matter

We investigate the presence of thermodynamic instabilities in a hot and dense nuclear medium where a phase transition from a gas of massive hadrons to a nearly massless baryon, antibaryon plasma can take place. The analysis is performed by requiring the global conservation of baryon number and zero net strangeness in the framework of an effective relativistic mean field theory with the inclusion of the Δ(1232)-isobars, hyperons and the lightest pseudoscalar and vector meson degrees of freedom. Similarly to the low density nuclear liquid-gas phase transition, we show that such a phase transition is characterized by both mechanical instability (fluctuations on the baryon density) that by chemical- diffusive instability (fluctuations on the strangeness concentration). It turns out that, in this situation, phases with different values of antibaryon-baryon ratios and strangeness content may coexist.     

Molecular dynamics simulation for the baryon-quark phase transition at finite baryon density

We study the baryon-quark phase transition in the molecular dynamics (MD) of the quark degrees of freedom at finite baryon density. The baryon state at low baryon density, and the deconfined quark state at high baryon density are reproduced. We investigate the equations of state of matters with different u-d-s compositions. It is found that the baryon-quark transition is sensitive to the quark width.     

Examining the crossover from the hadronic to partonic phase in QCD

A mechanism, consistent with color confinement, for the transition between perturbative and physical vacua during the gradual crossover from the hadronic to partonic phase is proposed. The essence of this mechanism is the appearance and growing up of a kind of grape-shape perturbative vacuum inside the physical one. A percolation model based on simple dynamics for parton delocalization is constructed to exhibit this mechanism. The crossover from hadronic matter to sQGP (strongly coupled quark-gluon plasma) as well as the transition from sQGP to weakly coupled quark-gluon plasma with increasing temperature is successfully described by using this model.     

Magnetized color flavor locked state and compact stars

The stability of the color flavor locked phase in the presence of a strong magnetic field is investigated within the phenomenological MIT bag model, taking into account the variation of the strange quark mass, the baryon density, the magnetic field, as well as the bag and gap parameters. It is found that the minimum value of the energy per baryon in a color flavor locked state at vanishing pressure is lower than the corresponding one for unpaired magnetized strange quark matter and, as the magnetic field increases, the energy per baryon decreases. This implies that magnetized color flavor locked matter is more stable and could become the ground state inside neutron stars. The mass-radius relation for such stars is also studied.     

Spatially modulated phase in the holographic description of quark-gluon plasma

We present a string theory construction of a gravity dual of a spatially modulated phase. Our earlier work shows that the Chern-Simons term in the five-dimensional Maxwell theory destabilizes the Reissner-Nordstr?m black holes in anti-de Sitter space if the Chern-Simons coupling is sufficiently high. In this Letter, we show that a similar instability is realized on the world volume of 8-branes in the Sakai-Sugimoto model in the quark-gluon plasma phase. Our result suggests a new spatially modulated phase in quark-gluon plasma when the baryon density is above 0.8Nf fm(-3) at temperature 150 MeV.     

Gapless color superconductivity

We present the dispersion relations for quasiparticle excitations about the color-flavor locked ground state of QCD at high baryon density. In the presence of condensates which pair light and strange quarks there need not be an energy gap in the quasiparticle spectrum. This raises the possibility of gapless color superconductivity, with a Meissner effect but no minimum excitation energy. Analysis within a toy model suggests that gapless color superconductivity may occur only as a metastable phase.     

Influence of Entropy on Composition and Structure of Massive Protoneutron Stars

Adjusting the suitable coupling constants in relativistic mean field (RMF) theory and focusing on thermal effect of an entropy per baryon (S) from 0 to 3, we investigate the composition and structure of massive protoneutron stars corresponding PSR J1614-2230 and PSR J0348+0432. It is found that massive protoneutron stars (PNSs) have more hyperons than cold neutron stars. The entropy per baryon will stiffen the equation of state, and the influence on the pressure is more obvious at low density than high density, while the influence on the energy density is more obvious at high density than low density. It is found that higher entropy will give higher maximum mass, higher central temperature and lower central density. The entropy per baryon changes from 0 to 3, the radius of a PNS corresponding PSR J0348+0432 will increase from 12.86 km to 19.31 km and PSR J1612-2230 will increase from 13.03 km to 19.93 km. The entropy per baryon will raise the central temperature of massive PNSs in higher entropy per baryon, but the central temperature of massive PNSs maybe keep unchanged in lower entropy per baryon. The entropy per baryon will increase the moment of inertia of a massive protoneutron star, while decrease gravitational redshift of a massive neutron star.     

Orientation dependence of center baryon density in central 0.52 GeV/n U-U collisions

With a relativistic transport model, We performed simulation for deformed UU collision with vast different orientation at CSR energy area corresponding to the high net-baryon density region in QCD phase diagram. By investigating the centrality and initial collision orientation dependence of the baryon density form, we found that those tip-tip like UU collisions with extended high density phase, which is very important for studying the nuclear EoS of high baryon density matter and the possible end-point of the phase boundary, are those events with small orientations (< 20°) in reaction plane and small impact parameter (< 2.4 fm). We have developed a measurable quantity that allows us to select those most interesting events (i.e. tip-tip like) in the experiment.