Mathematical Conversations

Stable commutator length (or scl) of group elements is a well-known, simple-to-define invariant, related to bounded cohomology and quasimorphisms. Yet its simple definition is a trap: many of the exciting developments around scl required "better"...

The theory of quantum cohomology was developed in the early 1990s by physicists working in the field of superstring theory.

Mathematicians then discovered applications to enumerative geometry, counting the number of rational curves of a given degree...