[1] Heidelberg Univ, Inst Theoret Phys, D-69120 Heidelberg, Germany
[2] Karlsruhe Inst Technol, Inst Expt Nucl Phys, D-76131 Karlsruhe, Germany
[3] Karlsruhe Inst Technol, Inst Theoret Phys, D-76131 Karlsruhe, Germany
[4] Univ Oregon, Inst Theoret Sci, Eugene, OR 97403 USA