  This paper aims to relate some properties of photon-like objects, considered
as spatially finite time-stable physical entities with dynamical structure, to
well defined properties of the corresponding electromagnetic strains defined as
Lie derivatives of the Minkowski (pseudo)metric with respect to the eigen
vector fields of the Maxwell-Minkowski stress-energy-momentum tensor. First we
recall the geometric sense of the concept of strain, then we introduce and
discuss the notion for photon-like objects (PhLO). We compute then the strains
along the eigen vectors of the stress-energy-momentum tensor $T_{\mu}^{\nu}$
and establish important correspondences with the divergence terms of
$T_{\mu}^{\nu}$ and the terms determining some internal energy-momentum
exchange between the two recognizable component-fields $F$ and $*F$ of a vacuum
electromagnetic field. The role of appropriately defined Frobenius curvature is
also discussed and emphasized. Finally, equations of motion and interesting
PhLO-solutions are given.
