Inhomogeneous Chiral Phases and Finite-Momentum Instabilities in the QCD Phase Diagram

par William R. Tavares (Rio de Janeiro State U., Brésil)

jeudi 24 sept. 2026, 14:00 → 15:00 Europe/Paris

Salle 1180, bâtiment E2 (Salle des séminaires )

Inhomogeneous chiral phases have long been considered a compelling possibility in dense strongly interacting matter. In effective models of QCD, spatially modulated condensates may occupy a sizable region of the phase diagram at low temperatures and intermediate-to-high baryon densities, frequently replacing the homogeneous first-order chiral transition. However, recent studies have emphasized that the predicted inhomogeneous region can depend strongly on the ultraviolet regularization scheme, raising a fundamental question: are these phases genuine medium-driven phenomena, or merely artifacts of the treatment of vacuum fluctuations?
In this talk, we revisit this question within the two-flavor Nambu–Jona-Lasinio model by investigating finite-momentum instabilities of the homogeneous phase using three commonly employed regularization schemes: a three-dimensional sharp cutoff, Pauli–Villars regularization, and proper-time regularization. We show that the apparent scheme dependence originates primarily from applying the ultraviolet regulator not only to divergent vacuum contributions, but also to convergent medium contributions. Once the latter are consistently left unregularized, the three schemes predict remarkably similar instability regions throughout the physically relevant parameter space.
These results overturn the usual interpretation that inhomogeneous chiral phases are intrinsically regulator dependent. Instead, they demonstrate that the finite-momentum instability is a robust property of dense fermionic matter, while the large discrepancies reported previously arise mainly from the regularization prescription rather than from the ultraviolet completion of the model. We will discuss the implications of this finding for the robustness of spatially modulated phases and for our understanding of the low-temperature, high-density region of the QCD phase diagram.