TOPICS
Search

Random-Cluster Model


A random-cluster model on a finite graph G=(V,E) is a measure phi_(p,q) on the measurable space (Omega,F) defined as follows. Let Omega={0,1}^E, whose elements are vectors omega=(omega(e):e in E), and let F be the sigma-algebra of all subsets of Omega. For each omega, set

 phi_(p,q)(omega)=1/Z(product_(e in E)p^(omega(e))(1-p)^(1-omega(e)))q^(k(omega)),
(1)

where here, 0<=p<=1 and q>0 are parameters, Z is the so-called partition function

 Z=sum_(omega in Omega){product_(e in E)p^(omega(e))(1-p)^(1-omega(e))}q^(k(omega)),
(2)

and k(omega) denotes the number of connected components of the graph (V,eta(omega)) where

 eta(omega)={e in E:omega(e)=1}.
(3)

The connected components of (V,eta(omega)) are called open clusters.

For a positive integer q and p<1, the substitution v=p/(1-p) identifies Z, up to the factor (1-p)^(|E|), with the q-state Potts model partition function.

In the above setting, the case q=1 corresponds to a model in which graph edges are open (i.e., omega(e)=1) or closed (i.e., omega(e)=0) independently of one another, a scenario which can be used as an alternative definition for the term percolation. For q!=1, edge states are generally dependent, giving a model of dependent percolation. On a forest, however, k(omega)=|V|-|eta(omega)|, and edge states are independent with open probability p/[p+q(1-p)].

For the critical model on the square integer lattice Z^2 with q=4 and p=2/3, Averous et al. (2026) reported convergence of its loops in the scaling limit to the conformal loop ensemble CLE_4. The associated four-state Potts model consequently has a conformally invariant scaling limit.


See also

AB Percolation, Bernoulli Percolation Model, Bond Percolation, Boolean Model, Boolean-Poisson Model, Bootstrap Percolation, Cayley Tree, Cluster, Cluster Perimeter, Conformal Loop Ensemble, Continuum Percolation Theory, Dependent Percolation, Discrete Percolation Theory, Disk Model, First-Passage Percolation, Fortuin-Kasteleyn Planar Map, Germ-Grain Model, Inhomogeneous Percolation Model, Lattice Animal, Long-Range Percolation Model, Mixed Percolation Model, Oriented Percolation Model, Percolation, Percolation Theory, Percolation Threshold, Polyomino, Potts Model, Random-Connection Model, Random Walk, s-Cluster, s-Run, Site Percolation

Portions of this entry contributed by Christopher Stover

Explore with Wolfram|Alpha

References

Averous, E.; Duminil-Copin, H.; He, T.; Lammers, P.; and Manolescu, I. "Conformal Invariance of the Planar Four-State Potts Model and Its Random-Cluster Representation." 6 Oct 2026. https://arxiv.org/abs/2610.08507.Grimmett, G. R. The Random-Cluster Model. Berlin, Germany: Springer-Verlag, 2009.

Referenced on Wolfram|Alpha

Random-Cluster Model

Cite this as:

Weisstein, Eric W., with contributions by Christopher Stover. "Random-Cluster Model." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/Random-ClusterModel.html

Subject classifications