  There are unsolved problems in physics leading to difficulties with Maxwell
equations that are not removed by and not directly associated with quantum
mechanics. Recently a number of extended and modified theories have therefore
been put forward. The two theories by the authors (AK and BL) are related to
this state. The first theory consists of a revised formulation of
electromagnetics with an electric vacuum charge density (BL), and the second is
a unified theory of Bivacuum, matter and fields (AK). In the first theory by BL
a space-charge current density arises from the condition of Lorentz invariance,
in addition to the conventional displacement current. The electron charge is
deduced from the theory, and it deviates by only one percent from its
experimental value. Two individual photon models are further investigated.
  In the second theory by AK a Bivacuum model is a consequence of development
of Dirac theory, pointing to equal probability of positive and negative energy.
The dynamic mechanism of [corpuscle (C) - wave (W)] duality is proposed. It
unifies the extended relativity and QM. For details see:
http://arxiv.org/abs/physics/0003001. The theories of BL and AK reinforce each
other, by having several points in common. There are the similarities with the
Dirac theory, symmetry with respect to the concepts of matter and antimatter,
the non-appearance of magnetic monopoles, a space- charge vacuum current in
addition to the displacement current, models of the leptons having an internal
vortex-like structure and force balance, photon models with a small but nonzero
rest mass and a slightly reduced velocity of propagation, and particle-wave
properties, explaining self-interference even of single electrons or photons.
