According to Cantor (Mathematische Annalen 21:545—586, 1883; Cantor's letter to Dedekind, 1899) a set is any multitude which can be thought of as one ("jedes Viele, welches sich als Eines denken läßt" ...

Effective descriptive set theory refines classical descriptive set theory by emphasising computability and algorithmic aspects in the study of definable sets and functions, particularly within Polish ...

In contrast to classical theory, quantum theory has the remarkable property that the state space of every system has continuously many pure states. These are states that can be seen as states of ...