Paul Dirac

Paul Ardrien Maurice Dirac [1902-1984] Quantum Physicist, Nobel Prize
- A natural introvert

- He self-paced Eddington's "Space, Time & Gravitation" to know Special & General Relativity inside out.

- 1925 encountered Quantum Mechanics: Heisenberg's 'lists'. Use Lie commutator AB-BA, not the product AB. Also Hamilton's formalism of mechanics Poisson bracket.

- Spin of electron: reverse, rotate 720 deg before the spin gets back to its original value.
For a ball, it is 360 degrees. Reason: Rotation of space = SO(3) but for quarternions & electrons = SU(2)
SU(2) is double in size of SO(3) -- "double cover" => 720=2x360

- Dirac didn't use group & quarternions

- 1927 X'mas 'spin matrices' (Spinors) which play the same role.

- Discovered Antimatter.

- 1956 Speech @ Moscow State University: 'A Physical law must possess mathematical beauty.'