The Hagedorn thermostat

At variance with previous understanding, a system H with a Hagedorn-like mass spectrum can sustain the unique temperature TH encoded in the spectrum itself. H imposes the same temperature to all emitted particles which are then in physical and chemical equilibrium with H and with each other. Coexistence between hadronic and partonic phases is thus completely characterized. This may explain the recurring constant physical and chemical temperature observed in several experiments. The near difference of H to fragmentation or coalescence makes this approach relevant to heavy-ion and elementary-particle collisions alike. The equation of state for a gas of H systems has been derived. (authors)