The Majumdar–Ghosh model is a one-dimensional quantum Heisenberg spin model in which the nearest-neighbour antiferromagnetic exchange interaction is twice as strong as the next-nearest-neighbour interaction. It is a special case of the more general J 1 - J 2 model, with J 1 = 2 J 2 . The model is named after Indian physicists Chanchal Kumar Majumdar and Dipan Ghosh.