On supersymmetric $D6$-$\bar D 6$ systems with magnetic fields

摘要

We study systems of $D6$ and $\bar D 6$ branes with non zero world-volumemagnetic fields in the weak coupling limit. We find two configurations forwhich the conditions for absence of tachyons in the spectra coincide exactlywith those found in the low energy effective theory approach, for the systemsto preserve 1/8 of the supersymmetries of the Type $IIA$ string theory vacuum.These conditions give rise to a four-parameter family of solutions in eachcase. We present further evidence of the stability of these systems bycomputing the lowest order interaction amplitude, verifying the no forcecondition as well as the supersymmetric character of the spectrum.