The gauge independence of the dynamical fermion mass generated through chiral symmetry breaking in QED in a strong, constant external magnetic field is critically examined. We show that the bare vertex approximation, in which the vertex corrections are ignored, is a consistent truncation of the Schwinger-Dyson equations in the lowest Landau level approximation. The dynamical fermion mass, obtai...

This paper conducts a stability, robustness and sensitivity analysis on a pointwise-optimal control law developed for dynamical systems. Many dynamical systems are described by complex nonlinear equations, which makes it difficult to design controllers for them. Pointwise-optimal control emerges as a viable design for such systems. We quantify the sources of errors for dynamical systems and pro...