Can Anything from Noether's Theorem Be Salvaged for Discrete Dynamical Systems?

摘要

The dynamics of a physical system is linked to its phase-space geometry by Noether's theorem, which holds under standard hypotheses including continuity. Does an analogous theorem hold for discrete systems? As a testbed, we take the Ising spin model with both ferromagnetic and antiferromagnetic bonds. We show that - and why-energy not only acts as a generator of the dynamics for this family of systems, but is also conserved when the dynamics is time-invariant.