## Spin Tensor of Electromagnetic Waves

**Authors:** Radi I. Khrapko

In the frame of the standard electrodynamics, a torque is calculated, which acts from a circularly
polarized electromagnetic beam with a plane phase front on an absorbing surface. And a moment of
momentum flux in the same beam is calculated in the frame of the same electrodynamics. It is
found that this torque is twice more than the moment of momentum flux. We have inferred that
the calculation of the electromagnetic angular momentum flux in the beam is incorrect. Namely,
this calculation takes only a moment of momentum into account as an angular momentum, and does
not take account of spin. An analysis of the field theory foundations of the electrodynamics
confirms this inference. Some changes in the field theory allow obtaining an electrodynamics'
spin tensor, which accompanies the Maxwell energy-momentum tensor. Using this spin tensor for
the beam yields the equality between the torque and the angular momentum flux. In this way, the
electrodynamics is completed by a spin tensor. A criticism of an AOP reviewer and my answer are
presented.

**Comments:** recovered from sciprint.org

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### Submission history

[v1] 1 Oct 2008

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