| Résume | Cardinal characteristics of the continuum are (definitions for) cardinals that are provably uncountable and at most the cardinality of the reals, but which may be strictly less than the cardinality of the continuum in universes where the Continuum Hypothesis fails. Many of the standard cardinal characteristics of the continuum are defined in terms of a relation holding almost everywhere, where "almost everywhere" means on all but a finite set. A very natural generalisation is to take "almost everywhere" to mean on all but a member of a given ideal. I will talk about what happens when we do this, with the density 0 ideal on the naturals as a focal example. |
