Contact geometry forms the mathematical basis of geometrical optics, in the same sense in which symplectic geometry forms the basis of classical mechanics. The ‘optical-mechanical analogy’...

Amid a series of changes that allows users to target LGBTQ+ people, Meta has deleted product features it initially championed.

A survey is given of the facts and fancies concerning the nonlinear Langevin or Itô equation. Actually, it is merely a pre-equation, which becomes an equation when an interpretation rule is added. The...