Concepts

Concepts before formalism. The big ideas of many-body physics recur across very different systems and methods, so here you can follow an idea — every topic that illustrates it, wherever it lives.

10 of 14 mapped concepts have topics so far; the greyed entries are the planned map.

Broken symmetry Ground states that choose less symmetry than their Hamiltonian — order parameters, rigidity, and Goldstone modes. 2 topics
Competing orders Several would-be ground states close in energy — the source of rich phase diagrams and intertwined order. 1 topic
Effective models Throwing away what does not matter at low energy — the art of writing the simplest model that still contains the physics. 1 topic
Emergence Behaviour that belongs to the whole, not the parts — the reason many-body physics is more than a sum of one-body problems. 2 topics
Localization When particles stop propagating — Mott (interaction-driven) and Anderson (disorder-driven) insulators. 3 topics
Phase transitions Qualitative change with a tuning parameter — first-order vs continuous, critical points, and quantum criticality. 2 topics
Quasiparticles Dressed excitations that behave like nearly-free particles — Landau's idea, its weight Z, and where it dies. 3 topics
Scaling & universality Why microscopically different systems share critical behaviour — relevant couplings, exponents, and fixed points. 1 topic
Strong correlations The regime where interactions dominate kinetic energy and independent-particle pictures fail. 2 topics
Symmetry The transformations a system respects — they organise the spectrum, fix selection rules, and predict what can happen. 1 topic