The developers of this phenomenon discovered a related melting phenomenon sometimes named for Halperin, Nelson, and Young in which there exists an intermediate hexatic substance.
An experimental confirmation of this phenomenon was done in triangular arrays of lead-tin junctions by Resnick et al. The renormalization group approach to this phenomenon requires using a "flow parameter" to derive normalized stiffness and fugacity equations. The developers of this phenomenon discovered a related melting phenomenon sometimes named for Halperin, Nelson, and Young in which there exists an intermediate hexatic substance. In all systems that undergo this phenomenon, the ratio of the spin-wave stiffness to the temperature of its occurrence is equal to two over pi. The system undergoing this phenomenon is equivalent to a (*) Coulomb gas in which winding number has replaced charge. This phenomenon, which is continuous and therefore has infinite order, can be derived by considering a pair of vortices in a gas binding to and unbinding from each other. For 10 points, name this phase transition that occurs in the two-dimensional XY model of a ferromagnet, in which long range order disappears at high temperatures, named for two physicists.
An experimental confirmation of this phenomenon was done in triangular arrays of lead-tin junctions by Resnick et al.
BKT transition [or Berezinskii-Kosterlitz-Thouless transition]