Quantum electrodynamics (QED) runs the show outside atomic nuclei, and quantum chromodynamics (QCD) runs it inside. This Q*D dynasty governs ordinary matter. The Q*Ds, which are purely based on abstract concepts, provide good impressionistic models of matter when supplemented with just two numerical parameters, and quite a lifelike rendering using four parameters (see my previous column, “Analysis and Synthesis,” Physics Today, May 2003, page 10). From these ingredients, we can synthesize a universe of mathematical possibilities that we believe, on good evidence, accurately mirrors the physical universe of materials and their chemistry.
In astrophysics, we study the behavior of very large amounts of matter over very long periods of time. Small but cumulative effects (gravity), or rare but transformative ones (weak interactions), which are negligible for most terrestrial and laboratory concerns, must be taken into account when we so widen our horizons. Yet by adding just two more...
