= Time reversal of a complex scalar field
{title2=$\hat T\phi(t,\boldsymbol x)\hat T^{-1}=\eta_T\phi(-t,\boldsymbol x)$}
For a charged <spin>-zero <complex scalar field>, time reversal preserves charge and can include an intrinsic phase. In its free-field <mode expansion of a free field>, <antiunitarity> conjugates the plane-wave coefficients. Relabel spatial momentum to its negative and compare the annihilation and creation terms: $\hat Ta(\boldsymbol p)\hat T^{-1}=\eta_Ta(-\boldsymbol p)$ and $\hat Tb^\dagger(\boldsymbol p)\hat T^{-1}=\eta_Tb^\dagger(-\boldsymbol p)$. Particle annihilation remains annihilation; unlike <charge conjugation>, this operation does not exchange particle and <antiparticle> operators.
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