Thermodynamic scaling and string dynamics in rotating holographic QCD

Abstract

We investigate the effect of finite angular velocity on the phase structure and Schwinger pair production in a holographic QCD model based on the Einstein--Maxwell--dilaton framework. Rotation is introduced through a boost construction that generates a stationary rotating geometry from the corresponding static background. We first study the thermodynamic phase diagram using the grand potential together with several response functions and show that all thermodynamic phase boundaries satisfy an exact scaling relation under rotation, implying that the rotating thermodynamic sector is completely determined by the corresponding static solution through a simple boost transformation. We then investigate confinement through the effective string tension and find that, consistent with the thermodynamic observables, rotation decreases the string confinement--deconfinement transition temperature and chemical potential. The corresponding phase boundary, however, no longer obeys the thermodynamic scaling relation. Consequently, the region in the phase diagram that is thermodynamically confined but string deconfined grows with angular velocity. We further study the Schwinger effect using the potential analysis approach. Rotation lowers both the confining and catastrophic critical electric fields and suppresses the height and width of the potential barrier, thereby enhancing pair production in both confined and deconfined phases. In the deconfined phase, rotation also generates a worldsheet horizon that limits the radial extent of connected string solutions and reduces both the maximum quark--antiquark separation and the deepest turning point of the energetically favored string. These results demonstrate that, while rotation acts trivially in the thermodynamic sector through an exact scaling law, it produces genuinely new effects in the string sector.