# Tag Info

In CFT, we are interested in the continuum limit, where we can classify classes of models at their critical points. By means of the Jordan-Wigner transformation one can construct a fermion operator out of the spin operators of the usual 2D Ising model. Then, the continuum critical Ising model is described by a massless real fermion: $$S=\frac 12\int d^2 z\... 0 The critical point of the Ising model in two dimensions is about$$ T= 2.269 \frac{J}{k_B}, where $J$ is a free parameter that can be interpred as the coupling between spins and has energy units. So by introducing $J$ (experimentally or by other calculation) and dividing by $k_B$ (Boltzmann's constant) you would get the temperature in Kelvin.