A rigorous formulation of Density Functional Theory for spinless fermions in one dimension

In this paper, we present a completely rigorous formulation of Kohn-Sham density functional theory for spinless fermions living in one dimensional space. More precisely, we consider Schrödinger operators of the form $H_N(v,w)=-\mathrm{\Delta }+{\sum }_{i\mathrm{\ne }j}^{N}w(x_i,x_j)+{\sum }_{j=1}^{N}v(x_i)$ acting on ${\wedge }^N{\mathrm{L}}^2([0,1])$, where the external and interaction potentials $v$ and $w$ belong to a suitable class of distributions. In this setting, we obtain a complete characterization of the set of pure-state $v$-representable densities on the interval. Then, we prove a Hohenberg-Kohn theorem that applies to the class of distributional potentials studied here. Lastly, we establish the differentiability of the exchange-correlation functional and therefore the existence of a unique exchange-correlation potential. We then combine these results to provide a rigorous formulation of the Kohn-Sham scheme. In particular, these results show that the Kohn-Sham scheme is rigorously exact in this setting.