P { σ σ } → → { σ σ ′ } P { σ σ ′ } → → { σ σ } = P r ( { σ σ ′ } | B . C . ) P r ( B . C . | { σ σ } ) P r ( { σ σ } | B . C . ) P r ( B . C . | { σ σ ′ } ) = p ⋅ ⋅ exp ⁡ ⁡ [ − − 2 β β ∑ ∑ < l , m > δ δ σ σ l , σ σ m J l m ] p ⋅ ⋅ exp ⁡ ⁡ [ − − 2 β β ∑ ∑ < l , m > δ δ σ σ l ′ , σ σ m ′ J l m ] = e − − β β Δ Δ E