In an ungauged N = 1 supergravity theory defined on an arbitrary Kahlerian manifold we compute the divergent one-loop corrections to the bosonic part of the effective action. Although the theory is not renormalizable such a calculation may be of relevance in view of the fact that N = 1 supergravities emerge as effective nonrenormalizable theories in the low-energy limit of some superstring models. In our calculations we have committed ourselves neither to a particular four-dimensional geometry nor to a particular Kahlerian manifold. We pay special attention to the one-loop scalar potential of the theory. We show that, by a proper redefinition of the metric, geometric objects such as scalar curvature can be made not to interact with the scalars and the definition of the potential of the theory becomes in this way unambiguous.PACS number(s): 04.65. +e 534

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In this work we find static black hole solutions in the context of two-dimensional dilaton gravity, which is modified by the addition of an R 2 term. This term arises from the one-loop effective action of a massive scalar field in its large mass approximation. The basic feature of this term is that it does not contribute to the Hawking radiation of the classical black hole backgrounds of the model. From this point of view, a class of the solutions derived are interpreted as describing back reaction effects. In particular it is argued that the evolution of a black hole via nonthermal signals is possible. Nevertheless, this evolution seems to be ''soft,'' in the sense that it does not lead to the evaporation of a black hole, leaving the Hawking radiation as the dominant mechanism for this process. ͓S0556-2821͑96͒05522-1͔

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