标题： 非冻结态下的动态手征对称性破缺${QED}_3$ 显示英文标题

标题： Dynamical Chiral Symmetry Breaking in Unquenched ${QED}_3$

摘要： 我们研究非冻结的${QED}_3$中的动力学手征对称性破缺，使用费米子和光子传播子的耦合Dyson--Schwinger方程组。 对于费米子-光子相互作用，我们采用一个满足其Ward--Green--Takahashi恒等式的假设。 我们给出了红外区域的自洽解析解以及所有动量的数值结果。 在朗道规范下，我们发现当味数达到临界值$N_f^{\mathrm crit} \approx 4$时存在相变。 在手征对称相中，传播子的红外行为由相互关联指数的幂律描述。 对于$N_f=1$和$N_f=2$，我们找到的小的手征凝聚值与最近格点计算的界限一致。 我们还研究了其他线性协变规范下的Dyson--Schwinger方程。 将它们的解与相应变换后的朗道规范解进行比较表明，冻结解近似具有规范协变性，但揭示了非冻结解存在显著的规范协变性破坏。 显示英文摘要

摘要： We investigate dynamical chiral symmetry breaking in unquenched ${QED}_3$ using the coupled set of Dyson--Schwinger equations for the fermion and photon propagators. For the fermion-photon interaction we employ an ansatz which satisfies its Ward--Green--Takahashi identity. We present self-consistent analytical solutions in the infrared as well as numerical results for all momenta. In Landau gauge, we find a phase transition at a critical number of flavours of $N_f^{\mathrm crit} \approx 4$. In the chirally symmetric phase the infrared behaviour of the propagators is described by power laws with interrelated exponents. For $N_f=1$ and $N_f=2$ we find small values for the chiral condensate in accordance with bounds from recent lattice calculations. We investigate the Dyson--Schwinger equations in other linear covariant gauges as well. A comparison of their solutions to the accordingly transformed Landau gauge solutions shows that the quenched solutions are approximately gauge covariant, but reveals a significant amount of violation of gauge covariance for the unquenched solutions.