Within a mean-field quark-meson model of strongly interacting matter, restricting the system to a finite spatial volume (via a low-momentum cutoff or discretized momentum modes with periodic/antiperiodic boundary conditions) shifts the location of the QCD critical endpoint that separates the crossover from a first-order chiral transition. The shift is significant below linear sizes of order 10 fm and depends on how the fermionic vacuum term is treated, which in turn reshapes the conserved-charge cumulant ratios used experimentally to search for the endpoint.
A mean-field quark-meson model study of how the finite spatial size of strongly interacting matter changes the QCD phase diagram. Finite size is imposed through momentum-space constraints -- a low-mo…