T r a c e ( T μ ν ) = T r a c e ( T μ . ν ) = T r a c e ( F μ α F α ν ) + 1 4 T r a c e ( η μ . ν F α β F α β ) {\displaystyle \mathrm {Trace} (T^{\mu \nu })=\mathrm {Trace} (T_{\mu }^{.\nu })=\mathrm {Trace} (F_{\mu \alpha }F^{\alpha \nu })+{\frac {1}{4}}\mathrm {Trace} (\eta _{\mu }^{.\nu }F_{\alpha \beta }F^{\alpha \beta })}
