In relativistic heavy-ion collisions, the strong electromagnetic (EM) field plays a crucial role in various quantum transport phenomena in the quark—gluon plasma (QGP), such as the chiral magnetic effect, chiral magnetic wave, and spin polarization of hyperons. The evolution of the EM field is significantly influenced by the medium response of the QGP, in which the chiral anomaly induced by the chiral chemical potential \mu_5 provides a unique quantum contribution that has not been systematically investigated.
Based on the 3+1D CLVisc relativistic viscous hydrodynamics with SMASH initial conditions, we numerically study the effect of the chiral chemical potential on the spatiotemporal evolution of EM fields in Au+Au collisions at \sqrts__NN=7.7—200 GeV with 20%—50% centrality. Within the weak-field approximation, the Maxwell equations are decoupled from the hydrodynamical evolution, and the chiral anomaly is introduced through the chiral conductivity \sigma_\chi\propto\mu_5 in the electric current density. The EM fields are solved using the finite-difference time-domain (FDTD) method in the Milne coordinate system.
The numerical results indicate that the chiral anomaly not only enhances the strength of the magnetic field eB_y and extends its lifetime, but also generates a stable sign-splitting and dipole-like spatial distribution of eB_y, which is remarkably different from the conventional case without chiral transport, as illustrated in Fig.1. For the electric field eE_y, the chiral anomaly considerably suppresses the late-time sign reversal, leading to a more stable field direction and spatial structure, as demonstrated in Fig.2. Moreover, the electromagnetic topological term \bf E\cdot\bf B, acting as the source term in the axial anomaly equation, shows a significantly slower decay and a systematically modified spatial distribution when the chiral anomaly is considered, as presented in Fig.3.
These results demonstrate that the chiral anomaly plays a dual role: it simultaneously modulates the temporal decay amplitude of electromagnetic fields and reshapes their spatial topological structure. The underlying physical mechanism is that the chiral imbalance of quarks in the QGP (characterized by \(\mu_5\)) is coupled to the electromagnetic field via the chiral magnetic effect (CME) current, which changes the helicity of the electromagnetic field and further leads to the restructuring of its spatial distribution. This work provides a refined and realistic description of electromagnetic field evolution in the QGP and offers new theoretical perspectives for understanding experimental signals associated with the chiral magnetic effect in relativistic heavy-ion collisions.