Dr. Chris Matzner, CITA "Stellar feedback, the ends of the IMF, and star cluster formation" Abstract: Star formation is sometimes modeled as the collapse of an isothermal gas, but this description misses the stars' own environmental impact. I will discuss feedback on two scales -- in the formation of single stars, and in the collective influence of stars during the birth of a star cluster -- concentrating on the stability of disk accretion and the consequences of protostellar outflows. Feedback is significant in determining the brown dwarf population, the stellar upper mass limit, the relation between the core and star mass functions, and the overall properties of dense and active stellar cluster-forming regions.