Stability of D brane Anti D brane Systems in Confining Gauge Theories

We study the stability of a special form of D brane embedding which is regarded as a bound state of D$_n$ and anti-D$_n$-brane embedded in a 10D supergravity background which is dual to a confining gauge theory. For D5 branes with $U(1)$ flux, their bound state configuration can be regarded as the baryonium vertex. For D branes of $n=6$ and 8 without the $U(1)$ flux, their bound states have been used to introduce flavor quarks in the dual supersymmetric Yang-Mills theory. In any case, it would be important to assure that they are free from tachyon instability. For all these cases, we could show their stability with respect to this point.