Numerical models

Formal rank--degree--coordinate models: an intersection ring, its grading, a degree map, Chern and Todd coefficients, and Riemann--Roch. Nothing here realizes a model in a real divisor space, carries a central charge, or names a wall; those are the demonstrations of Numerical/Examples/, which import this directory rather than the other way round.

A model is not a scheme. Each module states which hypotheses on an actual variety its coordinates are a shadow of, and none of them constructs the variety.