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=2×360

– 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.’


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