Lower critical dimension
= Lower critical dimension
{title2=$d_{\mathrm l}$}
The lower critical dimension is the spatial dimension at or below which fluctuations prevent the ordered phase associated with a proposed finite-temperature transition. A short-range model with discrete symmetry normally has $d_{\mathrm l}=1$, whereas continuous $O(2)$ symmetry has $d_{\mathrm l}=2$.