We now begin a study of D-branes that carry electric or magnetic fields on their world-volume. Open strings couple to these electromagnetic fields at their endpoints. Using the tools of T-duality we show that a D-brane with an electric field is physically equivalent to a moving D-brane with no electric field. The constraint that a D-brane cannot move faster than light implies that the strength of an electric field cannot exceed a certain maximum value. We also show that a Dp-brane with a magnetic field is T-duality equivalent to a tilted D(p − 1)-brane with no magnetic field. Alternatively, the magnetic field on the Dp-brane can be thought of as being created by a distribution of dissolved D(p − 2)-branes.
Maxwell fields coupling to open strings
Among the quantum states of open strings attached to a D-brane we found photon states with polarizations and momentum along the D-brane directions. We thus deduced that a Maxwell field lives on the world-volume of a D-brane. The existence of this Maxwell field was in fact necessary to preserve the gauge invariance of the term that couples the Kalb–Ramond field to the string in the presence of a D-brane. We also learned that the endpoints of open strings carry Maxwell charge.
Since any D-brane has a Maxwell field, it is physically reasonable to expect that background electromagnetic fields can exist: there may be electric or magnetic fields that permeate the D-brane.
Review the options below to login to check your access.
Log in with your Cambridge Aspire website account to check access.
If you believe you should have access to this content, please contact your institutional librarian or consult our FAQ page for further information about accessing our content.