Considering the density wave of scalar and pseudoscalar condensates, we study the response of quark matter to a weak external magnetic field. In an external magnetic field, the energy spectrum of the lowest Landau level becomes asymmetric about zero, which is closely related to chiral anomaly. This spectral asymmetry gives rise to spontaneous magnetization. This mechanism may be one of candidates for the origin of the strong magnetic field in magnetars. Furthermore, using the generalized Ginzburg-Landau(gGL) expansion, we show that magnetic susceptibility exhibits a peculiar feature.

In this letter, we investigate the anomalous Hall effect in dense QCD matter. When the dual chiral density wave which is the spatially modulated chiral condensate appears in the medium, it gives rise to two Weyl points to the single-particle energy-spectrum and then the anomalous Hall conductivity becomes nonzero. Then, dense QCD matter is analogous to the Weyl semimetal. The direct calculation of the Hall conductivity by way of Kubo's linear response theory gives the term proportional to the distance between the Weyl points. Unlike the Weyl semimetal, there appears the additional contribution induced by axial anomaly.

The effects of fluctuations are discussed around the phase boundary of the inhomogeneous chiral transition between the inhomogeneous chiral phase and the chiral-restored phase. The particular roles of thermal and quantum fluctuations are elucidated and a continuity of their effects across the phase boundary is suggested. In addition, it is argued that anomalies in the thermodynamic quantities should have phenomenological implications for the inhomogeneous chiral transition. Some common features for other phase transitions, such as those from the normal to the inhomogeneous Fulde-Ferrell-Larkin-Ovchinnikov state in superconductivity, are also emphasized.

We study the change of the effect of the current quark mass on the inhomogeneous chiral phase in the QCD phase diagram, and discuss the property of the phase transition by the generalized Ginzburg-Landau expansion. The strong external magnetic field spreads this phase over the low chemical potential region even if the current quark mass is finite. This implies that the existence of this phase can be explored by the lattice QCD simulation.

We discuss the features of the order-parameter fluctuations in the normal phase near the phase boundary and their effects on the phase transition from the normal to the inhomogeneous phase with spatially modulated order parameter. Focusing on the chiral symmetry breaking, i.e., inhomogeneous chiral transition, we consider the fluctuation of the chiral pair consisting of quark-antiquark or quarkhole pair within the two-flavor Nambu-Jona-Lasinio model in the chiral limit. We clarify the roles of quantum and thermal fluctuations and also argue that anomalies for thermodynamic quantities in the inhomogeneous chiral transition should lead to phenomenological implications.