The dispersion relation of an infinite form of these substances is modeled by the letters X, O, R, and L in the CMA diagram. When certain particles are “warm”, a term of 3 k-squared thermal speed squared appears in the Bohm–Gross dispersion relation of these substances. The term [read slowly] “two over the thermal de Broglie wavelength cubed” appears in an equation describing these substances named for (10[2])Meghnad (10[1])Saha. Discovering low-frequency oscillations in these substances won Hannes Alfvén (“all-VANE”) the 1970 Nobel Prize in Physics, who described these substances using MHD. The Debye (“duh-BYE”) length measures how well electric fields are screened in these substances, which are confined by a tokamak’s magnetic field in a potential fusion reactor design. For 10 points, name this high-energy fourth state of matter. ■END■