Currently, there are more than 100 confirmed multiple-planet systems. Moreover, a recent study by Kepler has identified 361 multiple-planet candidate systems. Investigating these systems would give us an important clue in understanding formation and evolution of planetary systems. In such multiple-planet systems, secular interactions among planets could play a significant role in determining th...

The effects of gas pressure gradients on the motion of solid grains in the solar nebula substantially enhances the efficiency of forming protoplanetary cores in the standard core accretion model in ’hybrid’ scenarios for gas/ice giant planet formation. Such a scenario is ’migration-enhanced’ core accretion which results from Epstein-drag induced inward radial migration of mm-sized grains needed...