D-branes in Melvin Background
In this paper we discuss D-branes in the Melvin background and its supersymmetric generalizations. In particular we determine the D-brane spectra in these backgrounds by constructing their boundary states explicitly, where some of the D-branes are supersymmetric. The results sensitively depend on whether the value of magnetic flux in the Melvin background is rational or irrational. For the rational case the D-branes are regarded as the generalizations of fractional D-branes in abelian orbifolds ${\bf C^n/Z_N}$ of type II or type 0 string theory. For the irrational case we found a very limited spectrum. Since the background includes the nontrivial H-flux, the D-branes will provide interesting examples from the viewpoint of the noncommutative geometry.