Onsager Reciprocal Relations

Symmetry relations among linear transport coefficients that hold in the near‑equilibrium linear response regime when microscopic dynamics respect time‑reversal symmetry.

A set of linear symmetry constraints on the transport coefficients L_ij that relate thermodynamic fluxes J_i to forces X_j in near-equilibrium irreversible thermodynamics, stating that for systems whose microscopic dynamics are time-reversal symmetric the phenomenological matrix is symmetric (L_ij = L_ji), with a generalized Onsager–Casimir form (L_ij = ε_i ε_j L_ji) when variables have defined pa