Resonant Impurity States in the D-Density-Wave Phase

We study the electronic structure near impurities in the d-density-wave (DDW) state, a possible candidate phase for the pseudo-gap region of the high-temperature superconductors. We show that the local DOS near a non-magnetic impurity in the DDW state is {\it qualitatively} different from that in a superconductor with $d_{x^2-y^2}$-symmetry. Since this result is a robust feature of the DDW phase, it can help to identify the nature of the two different phases recently observed by scanning tunneling microscopy experiments in the superconducting state of underdoped Bi-2212 compounds.