Symmetry

The transformations a system respects — they organise the spectrum, fix selection rules, and predict what can happen.

Every topic that illustrates this idea, drawn from across all subjects.

• The Hubbard Model Mott Physics in Correlated Lattices The minimal model of reference for the cuprates — one hopping amplitude and one on-site repulsion — together with its particle–hole symmetry, Green's functions, and the two limits (atomic and non-interacting) that already reveal the Mott insulator.