Twisted K-homology corresponds to D-branes in string theory. In this
paper we compare two different models of geometric twisted K-homology and get
their equivalence. Moreover, we give another description of geometric twisted
K-homology using bundle gerbes. We establish some properties of geometric
twisted K-homology. In the last part we construct T-duality isomorphism for
geometric twisted K-homology.Comment: We modify the statement about the six-term exact sequence of
geometric twisted K-homology. Some Typos are corrected. Comments are
welcome