A-tom, or Uni-form?

A lesson

The research team at the MPQ and University of Munich was the second group outside the USA to report BEC. The evidence for condensation emerged from time of flight measurements. A sharp peak in the velocity distribution was observed below a critical temperature. © Immanuel Bloch, (Quantum, Mainz)

So called Gross-Pitaevskii equation is the basis for the practical description of Bose-Einstein condensate in diluted gases. It resembles much the “ordinary" Schrödinger equation, apart from an interaction term. And  this term makes the difference: only including the  interaction between separated particles (attracting, repulsing) one gets a real, experimental situation.

 

Lev, the wavepacket describing an electron diverges in time. Does it result from a special, Gaussian form of the packet?
- No! Any packet diverges in time – this is asuperposition of waves with different lengths. Only a plane wave does not diverge in time.
- So, quantum mechanics does not describe electron as a stable object?
-Wrong! Electron is stable and point-like! Schrödinger’s equationdoes NOT describe the electron itself but the probability of finding the electron in a given point! 

- Lev, tell me what ideawas behind Your famous equation?
- In 1956 H. Hall and W. Vined in UK discovered a very interesting phenomenon - quantum vortexes in superfluid Helium. They were predicted by L. Onsager and R. Feynman, but we had no good theory. I thought on the subject for several years and finally, in 1961, being on vacations, I understood that the theory can be developed for the Bose-condensed gases, which were in fact created in 1975 only. I remember that Landau agreed with my theory not immediately,  but after several discussions.

Photos are from professor Pitaevskii’s 70th birthday dinner. Thanks! Asking questions: GK

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