174 Dirac equation, Quantum Electro Dynamics Nobel Prize

Inledning

”Problemet” som jag i denna text ska beskriva och redogöra för är, som titeln antyder, den ekvation som fått benämningen The Dirac Equation (Diracekvationen på svenska) samt begreppet Quantum Electro Dynamics (Kvantelektrodynamik på svenska) och hur dessa influerade Feynman till att vinna nobelpriset i fysik 1965 tillsammans med Julian Schwinger och Sin-Itiro Tomonaga2.
För att uppnå förståelse för dessa begrepp måste man backa tillbaka några steg i ledet eftersom att Kvantelektrodynamiken bygger på kvantmekaniken, samt elektrodynamiken.
Utöver det så bygger Diracekvationen på Schrödingerekvationen på det sättet att denna är en omformning av Schrödingerekvationen, Diracekvationen är på så vis den relativistisk motsvarigheten till Schrödingerekvationen. Den tar även hänsyn till den speciella relativitetsteorin. 3
”Problemtypen” är i högsta grad inom ämnesområdet fysisk, och beskrivs med hjälp av matematiska modeller.

Det kunskaper som krävs för att förstå detta på en fundamental nivå är av väldigt hög grad. Jag kommer således ge en inblick i några av ovanstående begrepp i hopp om att stärka er förståelse och insikt kring huvudämnet i fråga som är Kvantelektrodynamik och Diracekvationen samt hur detta ledde till ett nobelpris.

Citat från boken som "beskriver" "problemet".

...Within a week I was in the cafeteria and some guy, fooling around, throws a plate in the air. As the plate went up in the air I saw it wobble, and I noticed the red medallion of Cornell on the plate going around. It was pretty obvious to me that the medallion went around faster than the wobbling. I had nothing to do, so I start to figure out the motion of the rotating plate. I discover that when the angle is very slight, the medallion rotates twice as fast as the wobble rate--two to one. It came out of a complicated equation! Then I thought, "Is there some way I can see in a more fundamental way, by looking at the forces or the dynamics, why it's two to one?" I don't remember how I did it, but I ultimately worked out what the motion of the mass particles is, and how all the accelerations balance to make it come out two to one. I still remember going to Hans Bethe and saying, "Hey, Hans! I noticed something interesting. Here the plate goes around so, and the reason it's two to one is . . ." and I showed him the accelerations.He says, "Feynman, that's pretty interesting, but what's the importance of it? Why are you doing it?" "Hah!" I say. "There's no importance whatsoever. I'm just doing it for the fun of it." His reaction didn't discourage me; I had made up my mind I was going to enjoy physics and do whatever I liked. I went on to work out equations of wobbles. Then I thought about how electron orbits start to move in relativity. Then there's the Dirac Equation in electrodynamics. And then quantum electrodynamics. And before I knew it (it was a very short time) I was "playing"--working, really-- with the same old problem that I loved so much, that I had stopped working on when I went to Los Alamos: my thesis-type problems; all those old-fashioned, wonderful things. It was effortless. It was easy to play with these things. It was like uncorking a bottle: Everything flowed out effortlessly. I almost tried to resist it! There was no importance to what I was doing, but ultimately there was. The diagrams and the whole business that I got the Nobel Prize for came from that piddling around with the wobbling plate.1