The open string pair production revisited

The experimental efforts in testing the QED vacuum properties such as the Schwinger pair production in the presence of a strong electric field have so far not been successful. This raises a potential possibility regarding our current understanding of the usual QED vacuum picture complete or not. In this paper, we address this possibility by taking our own (1 + 3)-dimensional world as a visible D3 brane with a nearby (hidden) D3, placed parallel at a separation, in Type IIB superstring theory and by considering an analogous open string pair production process. We will first demonstrate that a single or an isolated D brane cannot in general give rise to this pair production in Type II superstring theories. To have such a pair production, we need at least two separated D branes, say two D3 given above. This two-D3 setup can be taken as a simplified version of the QED, resulting from the particle physics standard model constructed from the intersecting D-branes, in the sense that it captures the essential feature of the latter in that the pair production comes from the virtual pair of open string and anti open string connecting two different D branes, therefore along the direction(s) transverse to the visible brane. In other words, this pair production contains not only the signature of extra dimension(s) but also the information about the existence of the other (hidden) D branes relative to the visible world. We will use this simple setup to demonstrate analytically these and to show that the computed non-perturbative stringy pair production rate in the weak-field limit agrees precisely to the corresponding known non-perturbative QED one. In this context, the future detection of the Schwinger pair production may teach us lessons about the existence of extra dimension(s) and a potential source of dark matter among other things.