Sherrington and Kirkpatrick proposed the SK model in 1975, and solved it by the replica method. They discovered that at low temperatures, its entropy becomes negative, which they thought was because the replica method is a heuristic method that does not apply at low temperatures.
sherrington and kirkpatrick proposed the sk model in 1975 and solved it by the replica method they discovered that at low temperatures its entropy becomes negative which they thought was because the replica method is a heuristic method that does not apply at low temperatures