Above the chiral symmetry restoration crossover around $T_{ch}\sim 155$ MeV a new regime arises in QCD, a stringy fluid, which is characterized by an approximate chiral spin symmetry of the thermal partition function. This symmetry is not a symmetry of the Dirac Lagrangian and is a symmetry of the electric part of the QCD Lagrangian. In this regime the medium consists of the chirally symmetric and approximately chiral spin symmetric hadrons that are made of the chirally symmetric quarks connected into the color singlet compounds by a confining chromoelectric field. This regime is evidenced by the approximate chiral spin symmetry of the spatial and temporal correlators and by the breakdown of the thermal perturbation theory at the crossover between the partonic (the quark–gluon plasma) and the stringy fluid regimes at $\sim 3T_{ch}$. The chiral spin symmetry smoothly disappears above $\sim 3T_{ch}$ which means that the chromoelectric confining interaction gets screened. A direct evidence that the stringy fluid medium consists of densely packed hadrons is the pion spectral function that shows a distinct pion state and its first radial excitation above $T_{ch}$. Another direct evidence of the hadron degrees of freedom in the stringy fluid is the bottomonium spectrum with the 1S, 2S, 3S and 1P, 2P radial and orbital excitations that become broad with temperature. The hadrons between $T_{ch}$ and $\sim 3T_{ch}$ in the stringy fluid interact strongly which makes the stringy fluid more a liquid rather than a gas. We discuss how this chiral spin symmetric regime extends into the finite chemical potentials domain and present a qualitative sketch of the QCD phase diagram.

以上手性对称恢复交叉绕${吨}_{CH}～155$MeV 一种新的状态出现在 QCD 中，这是一种弦状流体，其特征在于热分配函数的近似手性自旋对称性。这种对称性不是狄拉克拉格朗日量的对称性，而是 QCD 拉格朗日量的电部分的对称性。在这种情况下，介质由手性对称和近似手性自旋对称的强子组成，这些强子由手性对称夸克组成，通过限制色电场连接到彩色单线态化合物中。空间和时间相关子的近似手性自旋对称性以及在部分子（夸克-胶子等离子体）和弦流体状态之间的交叉处的热扰动理论的崩溃证明了这种状态$～\mathrm{3个}{吨}_{CH}$. 手性自旋对称性在上方顺利消失$～\mathrm{3个}{吨}_{CH}$这意味着色电限制相互作用被屏蔽了。弦状流体介质由密集强子组成的直接证据是 pion 谱函数，该函数显示出不同的 pion 状态及其在上方的第一个径向激发${吨}_{CH}$. 弦状流体中强子自由度的另一个直接证据是具有 1S、2S、3S 和 1P、2P 径向和轨道激发的 bottomonium 光谱随温度变宽。之间的强子${吨}_{CH}$和$～\mathrm{3个}{吨}_{CH}$弦状流体中的相互作用强烈，这使得弦状流体更像是液体而不是气体。我们讨论了这种手性自旋对称状态如何延伸到有限化学势域，并给出了 QCD 相图的定性草图。