Order parameter statistics in the critical quantum Ising chain
arXiv:0802.1246 · doi:10.1103/PhysRevLett.100.165706
Abstract
In quantum spin systems obeying hyperscaling, the probability distribution of the total magnetization takes on a universal scaling form at criticality. We obtain this scaling function exactly for the ground state and first excited state of the critical quantum Ising spin chain. This is achieved through a remarkable relation to the partition function of the anisotropic Kondo problem, which can be computed by exploiting the integrability of the system.