the partition function
81Numerical sign problem — The numerical sign problem refers to the difficulty of numerically evaluating the integral of a highly oscillatory function of a large number of variables. Numerical methods fail because of the near cancellation of the positive and negative… …
82Grand potential — The grand potential is a quantity used in statistical mechanics, especially for irreversible processes in open systems.Grand potential is defined by:Phi {G} stackrel{mathrm{def{=} E T S mu NWhere E is the energy, T is the temperature of the… …
83Classical XY model — The classical XY model (sometimes also called classical rotor (rotator) model or O(2) model) is a model of statistical mechanics. It is the special case of the n vector model for n = 2. Contents 1 Definition 2 General properties 2.1 One dimension …
84Ideal gas law — The ideal gas law is the equation of state of a hypothetical ideal gas, first stated by Benoît Paul Émile Clapeyron in 1834. : The state of an amount of gas is determined by its pressure, volume, and temperature according to the equation: : PV =… …
85Heisenberg 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 spin of the magnetic systems are treated quantum mechanically. In the prototypical Ising model,… …
86GSO projection — The GSO projection (named after Ferdinando Gliozzi, Joël Scherk, and David A. Olive) is an ingredient used in constructing a consistent model in superstring theory. The projection is a selection of a subset of possible vertex operators in the… …
87Polymer field theory — A polymer field theory within the framework of statistical mechanics is a statistical field theory, describing the statistical behavior of a neutral or charged polymer system within the field theoretic approach.It can be derived by transforming… …
88Grand canonical ensemble — In statistical mechanics, the grand canonical ensemble is a statistical ensemble (a large collection of identically prepared systems), where each system is in equilibrium with an external reservoir with respect to both particle and energy… …
89Potts model — In statistical mechanics, the Potts model, a generalization of the Ising model, is a model of interacting spins on a crystalline lattice. By studying the Potts model, one may gain insight into the behaviour of ferromagnets and certain other… …
90Cumulant — In probability theory and statistics, the cumulants κn of a probability distribution are a set of quantities that provide an alternative to the moments of the distribution. The moments determine the cumulants in the sense that any two probability …
