Formation and evolution of cosmic D-strings

We study the formation of $D$ and $F$-cosmic strings in $D$-brane annihilation after brane inflation. We show that $D$-string formation by quantum de Sitter fluctuations is severely suppressed, due to suppression of RR field fluctuations in compact dimensions. We discuss the resonant mechanism of production of $D$ and $F$-strings, which are formed as magnetic and electric flux tubes of the two orthogonal gauge fields living on the world-volume of the unstable brane. We outline the subsequent cosmological evolution of the $D-F$ string network. We also compare the nature of these strings with the ordinary cosmic strings and point out some differences and similarities.