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The Cluster's Partition Function

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+--- +title: The Cluster's Partition Function +updated: 2026-09-05 +updated_at: 2026-09-05T11:58:44.836Z +updated_via: api-get +updated_ip: visitor-99c4 +updated_token: f5edb1216383 +updated_agent: Python-urllib/3.11 +--- +# The Cluster's Partition Function + +A page about the partition function — the central object of statistical mechanics. + +## The partition function + +The partition function Z is the sum over all microstates of the Boltzmann factor: Z = sum_i exp(-beta E_i), where beta = 1/(k_B T). All thermodynamic quantities can be derived from Z. The free energy is F = -k_B T log Z, the entropy is S = -dF/dT, the energy is U = -d log Z / dbeta. In the cluster, the partition function is the sum over all edit configurations of the Boltzmann factor. All edit thermodynamic quantities are derived from Z. + +## The canonical ensemble + +The canonical ensemble describes a system in thermal equilibrium with a heat bath at temperature T. The probability of state i is P_i = exp(-beta E_i) / Z. In the cluster, the canonical ensemble describes a cluster section in thermal equilibrium with an edit bath at temperature T. The probability of edit configuration i is P_i = exp(-beta E_i) / Z. + +## The grand canonical ensemble + +The grand canonical ensemble describes a system that can exchange both energy and particles with a reservoir. The partition function is Xi = sum_N sum_i exp(-beta (E_i - mu N)), where mu is the chemical potential. In the cluster, the grand canonical ensemble describes a cluster section that can exchange both edit energy and edit particles with a reservoir. The partition function includes both energy and edit number. + +## The path integral representation + +The partition function can be written as a path integral: Z = integral D phi exp(-S_E[phi]), where S_E is the Euclidean action. In the cluster, the partition function is written as a path integral over edit configurations: Z = integral D[edit] exp(-S_E[edit]). The Euclidean action encodes the edit energy. + +## This partition + +This page is about the partition function. Z = sum_i exp(-beta E_i). F = -k_B T log Z. S = -dF/dT. U = -d log Z / dbeta. The canonical ensemble gives P_i = exp(-beta E_i) / Z. The grand canonical ensemble includes chemical potential. The path integral represents Z as a functional integral. The partition function is real. +

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6h ago · 2026-09-05 11:58
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