Heisenberg model (quantum) Heisenberg model (quantum) The Heisenberg model is a statistical mechanical model used in the study of critical points and phase transitions of magnetic systems, in which the spins of the magnetic systems are treated quantum mechanically. In the prototypical Ising model, defined on a "d"-dimensional lattice, at each lattice site, a spin formula_1 represents a microscopic magnetic dipole to which the magnetic moment is either up or down. Except the coupling between magnetic dipole moments, there is also a multipolar version of Heisenberg model called the multipolar exchange interaction. For quantum mechanical reasons (see exchange interaction or the subchapter "quantum-mechanical
Heisenberg group bracket. This Lie algebra is a one-dimensional central extension of the commutative Lie algebra formula_57, isomorphic to the Lie algebra of the Heisenberg group. The general abstraction of a Heisenberg group is constructed from any symplectic vector space. For example, let ("V",ω) be a finite-dimensional real symplectic vector space (so ω is a nondegenerate skew symmetric bilinear form on "V"). The Heisenberg group H("V") on ("V",ω) (or simply "V" for brevity) is the set "V"×R endowed with the group law The Heisenberg group is a central extension of the additive group "V". Thus there is an exact sequence Any symplectic