Henri Poincaré
29 April 1854 – 17 July 1912

Henri Jules Poincaré, dubbed “the last universalist”, died one hundred years ago, on 17 July 1912.

One word: symmetry.

Class Invariance Conserved quantity
Proper orthochronous
Lorentz symmetry		 translation in time
(homogeneity)		 energy
translation in space
(homogeneity)		 linear momentum
rotation in space
(isotropy)		 angular momentum
Discrete symmetry P, coordinate inversion spatial parity
C, charge conjugation charge parity
T, time reversal time parity
CPT product of parities
Internal symmetry (independent of
spacetime coordinates)		 U(1) gauge transformation electric charge
U(1) gauge transformation lepton generation number
U(1) gauge transformation hypercharge
U(1)Y gauge transformation weak hypercharge
U(2) [U(1) × SU(2)] electroweak force
SU(2) gauge transformation isospin
SU(2)L gauge transformation weak isospin
P × SU(2) G-parity
SU(3) “winding number” baryon number
SU(3) gauge transformation quark color
SU(3) (approximate) quark flavor
S(U(2) × U(3))
[ U(1) × SU(2) × SU(3)]		 Standard Model