Charge, domain walls and dark energy
  One idea to explain the mysterious dark energy which appears to pervade the
Universe is that it is due to a network of domain walls which has frozen into
some kind of static configuration, akin to a soap film. Such models predict an
equation of state with w=P/rho=-2/3 and can be represented in cosmological
perturbation theory by an elastic medium with rigidity and a relativistic sound
speed. An important question is whether such a network can be created from
random initial conditions. We consider various models which allow the formation
of domain walls, and present results from an extensive set of numerical
investigations. The idea is to give a mechanism which prevents the natural
propensity of domain walls to collapse and lose energy, almost to the point
where a domain wall network freezes in. We show that when domain walls couple
to a field with a conserved charge, there is a parameter range for which charge
condenses onto the domain walls, providing a resistive force to the otherwise
natural collapse of the walls
