  In analogy to the Schwinger pair production in QED, there exists also the
so-called open string pair production for a system of two Dp branes, placed
parallel at a separation, with at least one brane carrying a worldvolume
electric flux, in Type II string theories. There is however no such pair
production if an isolated Dp brane carrying an electric flux is considered. The
produced open strings are directly related to the brane separation, therefore
to the extra-dimensions if taken from the viewpoint of a brane observer. This
pair production can be greatly enhanced if one Dp brane carries also a magnetic
flux. The largest pair production rate occurs for $p = 3$, i.e., the D3 brane
system, with the same applied fluxes. A detection of this pair production by
the brane observer as the charged particle/anti-charged particle pair one shall
signal the existence of extra-dimensions and therefore provides a potential
means to test the underlying string theories.
