PHYSICAL-PROPERTIES OF 4-DIMENSIONAL SUPERSTRING GRAVITY BLACK-HOLE SOLUTIONS

We consider the physical properties of four-dimensional black hole sol utions to the effective action describing the low energy dynamics of t he gravitational sector of heterotic superstring theory. We compare th e properties of the external field strengths in the perturbative solut ion to the full O(alpha') string effective action equations, to those of exact solutions in a truncated action for charged black holes, and to the Kerr-Newman family of solutions of Einstein-Maxwell theory. We contrast the numerical results obtained in these approaches, and discu ss limitations of the analyses. Finally we discuss how the new feature s of classical string gravity affect the standard tests of general rel ativity.