Foreword with a table of contents for Special IJMPD Issue on Spacetime
  Structure and Electrodynamics
  In the last two decades we have seen important mutual stimulations between
the community working on electrodynamics of continuous media and the community
working on spacetime structure. This is highlighted by the publication of two
important monographs from two communities: Foundations of Classical
Electrodynamics by F. W. Hehl and Yu. N. Obukhov (Birkh\"auser, Boston 2003)
and Differential Forms in Electromagnetics by I. V. Lindell (IEEE Press-Wiley,
Piscataway, NJ 2004; see also a new book "Multiforms, Dyadics, and
Electromagnetic Media" by the same author in 2015). Starting around 1960,
magnetoelectric effects and magnetoelectric media have been a focus of study.
Somewhat later, the constitutive tensor density framework was used to construct
spacetime structure theoretically and empirically. Earlier, in putting Maxwell
equations into a form compatible with general relativity, Einstein noticed that
the Maxwell equations can be formulated in a form independent of the metric
gravitational potential in 1916; only the constitutive tensor density depends
on the metric. This was followed by further stimulating and clarifying works of
Weyl in 1918, Murnaghan in 1921, Kottler in 1922 and Cartan in 1923. Year 2016
is the centennial of the start of this historical development. International
Journal of Modern Physics D of World Scientific is celebrating the occasion by
publishing this special issue on Spacetime Structure and Electrodynamics. We
have invited researchers to submit original research articles that would
contribute to a better understanding of the phenomena inherent to spacetime
structure and electrodynamic media.
