Boundary States of D-Branes and Dy-Strings

Polchinski's recent construction of Dirichlet-branes of R-R charges, together with Witten's mechanism for forming bound states of both NS-NS charges and R-R charges, provides a rigorous method to treat these dy-branes. We construct the massless sector of boundary states of D-branes, as well as of dy-strings of charge $(p,1)$. As a consequence, the string tension formula predicted by duality in the type IIB theory is obtained.