Ledoux or Schwarzschild: Is that still the question?

Convection is a key process in stellar evolution which transports energy, mixes matter and shapes the internal structure of stars. Convective boundary mixing, often known as overshoot, increases the extent of convective regions and is essential for the creation of the ¹³C-pocket, the s-process site in low-mass stars. In the case of massive stars, several recent studies have shown a sensitive dependence of the pre-supernova structure and its explosion likelihood on the complex convective history. Despite the importance of convection, its impact in stellar evolution is blurred by missing details and large inconsistencies and uncertainties in 1D stellar evolution codes. One longstanding problem is the treatment of convective boundaries. Here, we will present the effects of some uncertainties, such as the convective boundary location and the amount of convective boundary mixing, and show how they impact the stellar structure, evolution and some implications for nucleosynthesis. Also, we will highlight which 1D model predictions are subject to the largest uncertainties.