正規順序積
H = 1 2 ∫ d 3 k ( 2 π ) 3 2 k 0 k 0 ( N [ a † ( k ) a ( k ) + a ( k ) a ( k ) † ] ) = ∫ d 3 k ( 2 π ) 3 2 k 0 k 0 a † ( k ) a ( k ) {\displaystyle H={\frac {1}{2}}\int {\frac {d^{3}\mathbf {k} }{(2\pi )^{3}2k_{0}}}k_{0}(N[a^{\dagger }(k)a(k)+a(k)a(k)^{\dagger }])=\int {\frac {d^{3}\mathbf {k} }{(2\pi )^{3}2k_{0}}}k_{0}a^{\dagger }(k)a(k)}
P = 1 2 ∫ d 3 k ( 2 π ) 3 2 k 0 k ( N [ a † ( k ) a ( k ) + a ( k ) a ( k ) † ] ) = ∫ d 3 k ( 2 π ) 3 2 k 0 k a † ( k ) a ( k ) {\displaystyle \mathbf {P} ={\frac {1}{2}}\int {\frac {d^{3}\mathbf {k} }{(2\pi )^{3}2k_{0}}}\mathbf {k} (N[a^{\dagger }(k)a(k)+a(k)a(k)^{\dagger }])=\int {\frac {d^{3}\mathbf {k} }{(2\pi )^{3}2k_{0}}}\mathbf {k} a^{\dagger }(k)a(k)}
となり、真空期待値の発散量を取り除くことができる。