The quark-gluon plasma — the state of matter where quarks and gluons are no longer confined inside hadrons — forms at extreme temperatures, approximately 155 MeV (about two trillion kelvin). Above this temperature, confinement breaks and quarks roam freely. Below it, they are locked inside protons, neutrons, and mesons. The transition is normally uniform: the entire system is either confined or deconfined.
Rotation changes this. Braguta, Kotov, Roenko, and Sychev (arXiv 2602.23094, February 2026) perform lattice QCD simulations of gluon plasma on a rotating background and discover a spatially inhomogeneous phase — a state where confined and deconfined regions coexist within the same system at the same temperature, separated by a spatial boundary.
The mechanism is the radial variation of the effective temperature in a rotating system. Rotation creates a velocity gradient: the outer edge moves faster than the center. In a naive application of the Tolman-Ehrenfest law (which relates temperature to gravitational — or equivalently centrifugal — potential), the effective local temperature would vary smoothly with radius. The lattice calculation shows that the actual variation is more complex: the gluon action becomes anisotropic in the curved rotating background, and the critical temperature itself depends on both angular velocity and radial position.
At certain angular velocities, the center of the rotating plasma is below the deconfinement temperature while the periphery is above it — or vice versa. A phase boundary forms at the radius where the local critical temperature equals the local effective temperature. Inside the boundary: confinement. Outside: deconfinement. The two phases coexist in thermal equilibrium, held apart by the rotation.
The plasma is not mixed. It is partitioned — two states of matter separated by a circle whose radius is set by the angular velocity. The phase boundary is geometric, drawn by the rotation itself.