Reduced Density Matrix Functional Theory for Canonical Ensemble in Finite Basis Set

Explore a 41-minute lecture by Sarina Sutter from Vrije Universiteit examining Reduced Density Matrix Functional Theory for the canonical ensemble in finite basis set at elevated temperature. Recorded during IPAM's Optimal Transport for Density Operators workshop, this presentation investigates how temperature inclusion guarantees differentiability of the universal functional by ensuring all states are occupied but not fully occupied in fermionic systems. The talk demonstrates how convexity of the universal functional and invertibility of the potential-to-1RDM map proves the subgradient contains only one element, which establishes differentiability and allows for characterization of v-representable 1RDMs in this theoretical framework.