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C. B. Agnor (University of Colorado, Southwest Research Institute), W. R. Ward (Southwest Research Institute)
The current model of planetary accretion is divided into three stages: km-sized planetesimal formation, planetary embryo formation, and the collisional accumulation of embryos into planets. This model has been generally successful at modeling the formation of systems resembling the inner planets (e.g.\ Wetherill 1994). However recent numerical integrations of late stage accretion in the terrestrial region have tended to produce planets with eccentricities about a factor of 2 higher than their terrestrial counterparts (Chambers and Wetherill 1998; Agnor, Canup and Levison 1999). Furthermore, attempts to extend the canonical model to the late stage accretion of Uranus and Neptune near their current locations have failed to account for their formation within the age of the solar system. However, these late stage models have included only gravitational and collisional interactions among the planetary embryos and have neglected the dynamical interactions with the disk of smaller planetesimals that likely co-exists with the embryos. Thus, it seems plausible that the discrepancies between the observed planets and model results are due, in part, to the neglect of any disk-planet interactions. Here we consider whether a damping mechanism such as apsidal waves (Ward and Hahn 1998; Agnor and Ward 2000) that exchanges angular momentum but not energy between embryos and the disk can alter the timescale and outcome of the accretion process.