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Inside-Out Planet Formation (IOPF) is a theory addressing the origin ofSystems of Tightly-Packed Inner Planets (STIPs) via {\it in situ} formation andgrowth of the planets. It predicts that a pebble ring is established at thepressure maximum associated with the dead zone inner boundary (DZIB) with aninner disk magnetorotational instability (MRI)-active region. Using direct$N$-body simulations, we study the collisional evolution of planetesimalsformed from such a pebble ring, in particular examining whether a singledominant planet emerges. We consider a variety of models, including some inwhich the planetesimals are continuing to grow via pebble accretion. We findthat the planetesimal ring undergoes oligarchic evolution, and typically turnsinto 2 or 3 surviving oligarchs on nearly coplanar and circular orbits,independent of the explored initial conditions or form of pebble accretion. Themost massive oligarchs typically consist of about $70\%$ of the total mass,with the building-up process typically finishing within $\sim 10^5$ years.However, a relatively massive secondary planet always remains with$\sim30-65\%$ of the mass of the primary. Such secondary planets haveproperties that are inconsistent with the observed properties of the innermostpairs of planets in STIPs. Thus, for IOPF to be a viable theory for STIPformation, it needs to be shown how oligarchic growth of a relatively massivesecondary from the initial pebble ring can be avoided. We discuss somepotential additional physical processes that should be included in the modelingand explored as next steps.

Inside-Out Planet Formation: VI. Oligarchic Coagulation of Planetesimals from a Pebble Ring?