For 10 points, name this model of ferromagnetism named for a German Physicist.
A computer that uses this non-laser system to solve Max-Cut optimization problems was developed by Yamamoto et al using light pulses in an optical cavity. Symmetries between high and low temperatures in this system are applied in the Kramers-Wannier duality to find that a dimensionless quantity for this system is "one half log of quantity one plus square root of two close quantity." This system can be solved by constructing a partition function via the trace of the product of transfer matrices. That method was developed by (*) Lars Onsager. This model tries to minimize energy by allowing dipole moments of neighboring particles to interact with each other. The 1D version of this model notably does not allow phase transitions. For 10 points, name this model of ferromagnetism named for a German Physicist.
A computer that uses this non-laser system to solve Max-Cut optimization problems was developed by Yamamoto et al using light pulses in an optical cavity.
Ising model [accept 2-D Ising model or other specific instances]