We study a quotient Conformal Field Theory, which describes a 3 + 1 dimensional cosmological spacetime. Part of this spacetime is the Nappi-Witten (NW) universe, which starts at a “big bang” singularity, expands and then contracts to a “big crunch” singularity at a finite time. The gauged WZW model contains a number of copies of the NW spacetime, with each copy connected to the preceeding one a...

We consider spacetimes N satisfying some structural conditions, which are still fairly general, and prove convergence results for the leaves of an inverse mean curvature flow. Moreover, we define a new spacetime N̂ by switching the light cone and using reflection to define a new time function, such that the two spacetimes N and N̂ can be pasted together to yield a smooth manifold having a metric ...

Power system voltage security is improved by optimizing reactive power dispatch (ORPD). ORPD problem is a multi-constrained, multi-objective problem involving both continuous and discrete control variables. An efficient optimization technique is needed for handling such a challenging objective function. Generator bus voltages, transformer tap positions and shunt Var compensator settings are the...