Open string instability in background electric fields

The propagation of bosonic open strings in the presence of background electric fields is examined. For neutral strings (for which the charges on the ends are equal and opposite) in weak fields the string polarizes, altering its spectrum. Above a critical value of the electric field, qEc = T, a classical instability develops in which those transverse string modes that oscillate parallel to the field develop negative squared-masses. For strings with overall charge, the dominant instability in weak fields consists of pair-production, at a constant rate per unit volume, until the classical instability is reached at the critical field, Ec. Although it is in th regime for which the classical instability dominates, it is noteworthy that (modulo tachyons) the pair-production rate goes to zero for infinite fields.