Finite-Size Effects on the Density-Driven Deconfinement Phase Transition in QCD

We investigate finite-size effects on the density-driven deconfinement phase transition (DPT) in Quantum Chromodynamics (QCD) using a model of coexisting hadronic and quark–gluon plasma (QGP) phases in a finite volume. The QGP phase is modeled via the MIT bag approach, explicitly incorporating the color-singletness constraint to account for the color confinement. As a continuation of our previous work, in the present study, we will analyze the first and second chemical derivatives of the order parameter across a range of quark chemical potentials (μ), at fixed temperature (T) and for several volume (V) selections, to determine the effective transition point in a finite volume. Our results reveal that the effective transition chemical potential μ_c(V) shifts to higher values as the system size decreases, highlighting the pronounced influence of finite-volume effects. Moreover, the rapid variations in the order parameter and its chemical susceptibility at the transition in large volumes, are rounded off in small volumes, and the transition region is smeared out, acquiring a width δµ(V) which increases with decreasing volume. These findings provide a comprehensive understanding of how finite-volume constraints influence the QCD phase structure, offering important insights for interpreting results from heavy-ion collisions and other high-energy experiments where the system size is inherently limited.