Dirac (a,-m)=0 If p=0 0 0 u@)- 0 ，u 0 0 1 0 0 1 If p#0: Two solutions for E>0: (and two for E<0) u) with: - 1 唱 :=B+m G.p 1 u唱= 豆=E+m 6…p 0 E十m 0 E+m Dirac (o-m)=0 -( 1 0 0 1 n四= u2)= G·p/(E+m) 0 0 G●p/(E+m yis 4-component spinor 4 solutions correspond to fermions and anti-fermions with spin+1/2 and-1/2 55 If p=0 If p≠0: Two solutions for E>0: (and two for E<0) with:                  0 / 0 1 )1( mEp u                   mEp u / 0 1 0 )2( 