Gibbs Random Field

Given a graph $G=\{V,E\}$, a family of random variables $F=\{F_{i}\}_{i=1}^{N}$ is called a Gibbs random field w.r.t. G iff its configuration, f, follows a Gibbs distribution:$P(f)=Z^{-1}\times e^{-U(f)/\lambda _{T}}$. $U(f)$ is called energy function. Z is normalizing constant called the partition function and $\lambda _{T}$ is called the temperature.