Are electrons mere billiard-balls?

Are pathologists becoming mere technicians?

a Nichols L. Are pathologists becoming mere technicians? [editorial]. How many hours each workday do you spend interacting with a computer screen instead of a person? As a pathologist, if you are signing out digital slides, flow cytometry or molecular diagnostic tests, interacting with a computer screen instead of a human being probably takes up most of your workday. Looking at glass slides is ...

Nonnegative Grassman Chambers Are Balls

Classically, the notion of total positivity referred to matrices all of whose minors had positive determinants. Lusztig generalized this notion substantially ([L1],[L2],[L3]) introducing the nonnegative part of an arbitrary reductive group, as well as the nonnegative part of a flag variety. Lusztig proved that the latter is always contractible and it has been conjectured to always be homeomorph...

Periodic Billiard Orbits Are Dense in Rational Polygons

We show that periodic orbits are dense in the phase space for billiards in polygons for which the angle between each pair of sides is a rational multiple of π.

4 Electrons Are Cheap ; Society Is Dear

Circular Billiard

We analyze the problem of perfectly elastic billiard on a circular table with exactly one permitted bounce. We present a new and intuitively appealing geometric derivation of the solution. Analyzing the solution with respect to the number of permitted paths for any given scenario, we nd an analytical expression for a separatrix between regions with two and four solutions. We identify and discus...