Facebook Twitter Instagram YouTube

Slippery Wave Functions

Event Details

Event Dates: 

Wednesday, April 17, 2013 - 4:00pm

Seminar Location: 

  • Duane Physics Room G1B20

Speaker Name(s): 

Leo Kadanoff

Speaker Affiliation(s): 

University of Chicago
Seminar Type/Subject

Scientific Seminar Type: 

  • Physics Department Colloquium

Event Details & Abstract: 

Superfluids and superconductors are ordinary matter that show a very surprising behavior at low temperatures. As its temperature is reduced, materials of both kinds can abruptly fall into a state in which they will support a persistent, essentially immortal, flow of particles. These flows differ from anything in classical physics in that they produce neither friction nor resistance. A major accomplishment of Twentieth Century physics was the development of an understanding of this very surprising behavior via the construction of partially microscopic and partially macroscopic quantum theories of superfluid helium and superconducting metals. Such theories come in two parts: a theory of the motion of particle-like excitations, called quasiparticles, and of the persistent flows themselves via a huge coherent excitation, called a condensate. The quasiparticles are described by giving the quasiparticle energy as a function of the quasiparticle momentum. The condensate is described by giving its quantum wave function.Two people, above all others, are credited with for the construction of the quasi-particle side of the theories of these very special low-temperature behaviors: Lev Landau and John Bardeen.  Curiously enough, they partially ignored and partially downplayed the importance of the condensate wave function.  In both cases, this partial neglect of the actual superfluid or superconducting flow interfered with their ability to assess the subsidiary advances that occurred immediately after their celebrated work on quasiparticles.Some speculations are offered about the source of this unevenness in the judgments of these two leading scientists