Réponse de R.B. Laughlin à un message de félicitations
Date: Wed, 14 Oct 1998 14:23:32 -0700 From: RHS Linux User <rbl@large.stanford.edu> Subject: Thank You 14 Oct 98 Ladies and Gentlemen, I want to thank you all for taking the time to write on the. occasion of the Nobel Prize announcement yesterday. It was pretty wonderful, I assure you, but the best part of all was powering up my computer this morning and finding this vast list of messages from well-wishers. I have read every one - notwithstanding the fact that I am perfectly capable of writing a macro that skims off the addresses - and typed every return address by hand. It is worth the time to look thoughtfully through this list, and I urge you to do it, for it contains names from many nations, many disciplines, and many walks of life, and is a powerful statement about what science is. John Muir was a great writer as well as a great naturalist, and one of his most beautiful images is of the waters of small mountain streams rejoicing on their way down to the sea. The messages you have sent me are all like that. They rejoice together in the elegance of these experiments, both the discoveries of Horst and Dan and those of Klaus von Klitzing that went before, and of the understanding of nature to which they lead. What a wonderful thing. Thank you for helping us celebrate this occasion in the most appropriate way imaginable. Bob Laughlin
Résumé tiré de PhysNews, 13 oct. 98 THE 1998 PHYSICS NOBEL PRIZE goes to Robert B. Laughlin of Stanford, Horst L. Stormer of Columbia, and Daniel C. Tsui of Princeton for their work on the fractional quantum Hall effect, a drama acted out in the two-dimensional world at the interface between two semiconductor crystals. As is the case with quantum phenomena, the act of confinement (the two-dimensional electron gas, or 2DEG, imprisoned between the semiconductors) leads to quantization. A plot of Hall conductivity versus field strength is not linear but stepwise. In other words, nature does not permit just any resistance, but only certain resistances dictated by fundamental quantum principles. The specific choice of semiconductor does not play a part. Klaus von Klitzing discovered this "quantum Hall effect" in 1980 and would win the physics Nobel Prize in 1985. So exacting is the quantization of conductivity (better than a part in many millions) that von Klitzing's experiment has since been used to define the unit of resistance. Stormer and Tsui would carry this research further. At even colder temperatures and higher magnetic fields, they discovered steps within the steps. This "fractional quantum Hall effect" (FQH) was at first hard to explain. Robert Laughlin surmised that the electrons were combining with the flux quanta of the magnetic field. One side effect of Laughlin's conjecture was that excitations of the FQH electron ensembles could have fractional charges. That is, the ensembles acted as if they were supporting particles (quasiparticles) with an electrical charge which was a non-integral multiple of the basic electron charge. In 1997 this hypothesis was experimentally verified in Israel and France. (Background: Updates 205 and 335; Physics Today, June 81, July 83, Dec 85, Jan 88, Jul 93, Oct 97, Nov 97; Science 19 Sep 97; Nature, 11 Sep 97.)
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Réponse de Walter Kohn à un message de félicitations d'André-Bandrauk
Date: Thu, 15 Oct 1998 18:47:42 -0400 From: Andre Bandrauk <andre.bandrauk@courrier.usherb.ca> To: tremblay@physique.usherb.ca >From: Andre Bandrauk <andre.bandrauk@courrier.usherb.ca> >Subject: Re: chemistry nobel prize > >>X-Sender: kohn@sbphy.physics.ucsb.edu >>Date: Thu, 15 Oct 1998 14:25:14 -0800 >>To: Andre Bandrauk <andre.bandrauk@courrier.usherb.ca> >>From: kohn@physics.ucsb.edu (Walter Kohn) >>Subject: Re: chemistry nobel prize >> >>>congratulations from the dept here at Sherbrooke. >>>I remember you did spend some time here during the war under quite >>>inauspicious circumstances.In any case well done and may you keep working >>>brilliantly as you have.With opur best wishes >>> \|/ Andre D. Bandrauk, Ph.D., FRSC >>> ----------- * - Dept. de Chimie/Fac. des Sciences >>> /|\ Universite de Sherbrooke (Quebec) J1K 2R1 >>> andre.bandrauk@courrier.usherb.ca >>> tel: 819-821-7098 >>> fax: 819-821-8017 >> >>Dear Andre, >> Sherbrooke wasn't that bad during the war (in fact I picked up quite a >>bit of science in the camp school) and my recent visit was very pleasant. >> Many thanks for your kind words, >> Walter >> >> >>--------------------------------------- >>Professor Walter Kohn >>Department of Physics >>University of California >>Santa Barbara, CA 93106 >> >>Phone: (805) 893-3061 >>Fax: (805) 893-3307 >>---------------------------------------- >> Résumé tiré de PhysNews, 15 octobre 98: THE 1998 NOBEL PRIZE FOR CHEMISTRY goes to Walter Kohn of the University of California at Santa Barbara and John A. Pople of Northwestern University for their contributions toward establishing computational chemistry. The Nobel citation quoted P.A.M. Dirac to the effect that although the basic quantum laws governing large parts of physics and chemistry are known, progress will still be obstructed by the fact that the pertinent equations are too difficult to solve. Kohn's solution was "density-functional theory," which describes atomic and molecular bonding not by accounting for the motions of all the participating electrons, but rather by specifying the effective density of electrons, making the whole problem much more computationally tractable. Pople wrote a number of computer programs over the years combining new quantum chemistry insights with the increasing power of computers. Both Kohn and Pople are as much physicist as chemist. Kohn was head of the Institute of Theoretical Physics in Santa Barbara for 1979-1984.