Kalb-Ramond field strength ($H=dB$)

The three-form field strength of the Kalb–Ramond field is $H=dB$. Its components are $H_{mnp}={\partial }_m{B}_{np}+{\partial }_n{B}_{pm}+{\partial }_p{B}_{mn}$. In flat spacetime the free equation is ${\partial }^m{H}_{mnp}=0$.