they ran computer simulations of 8500 planetary systems to see how giant planets could sometimes MIGRATE in close to the star and they got some statistics of what one might expect. I cannot vouch for this paper, or say how it stacks up compared with other similar papers, but this business of hot Jupiters is a great puzzle so I figure anything along these lines that might give some answers could be interesting. the paper has been accepted for publication in a peer-review journal so that is one good sign at least. if someone checks it out please let us know how good a paper and if it does help answer why there are so many giant planets are in close to their stars (like as close as Mercury, or closer) http://arxiv.org/abs/astro-ph/0505234 Giant Planet Migration through the Action of Disk Torques and Planet Scattering Althea V. Moorhead, Fred C. Adams 46 pages including 15 figures; accepted to ICARUS "This paper presents a parametric study of giant planet migration through the combined action of disk torques and planet-planet scattering. The torques exerted on planets during Type II migration in circumstellar disks readily decrease the semi-major axes, whereas scattering between planets increases the orbital eccentricities. This paper presents a parametric exploration of the possible parameter space for this migration scenario using two (initial) planetary mass distributions and a range of values for the time scale of eccentricity damping (due to the disk). For each class of systems, many realizations of the simulations are performed in order to determine the distributions of the resulting orbital elements of the surviving planets; this paper presents the results of 8500 numerical experiments. Our goal is to study the physics of this particular migration mechanism and to test it against observations of extrasolar planets. The action of disk torques and planet-planet scattering results in a distribution of final orbital elements that fills the a-e plane, in rough agreement with the orbital elements of observed extrasolar planets. In addition to specifying the orbital elements, we characterize this migration mechanism by finding the percentages of ejected and accreted planets, the number of collisions, the dependence of outcomes on planetary masses, the time spent in 2:1 and 3:1 resonances, and the effects of the planetary IMF. We also determine the distribution of inclination angles of surviving planets and the distribution of ejection speeds for exiled planets."