Concentrated sets and $γ$-sets in the Miller model

Abstract: Using combinatorial covering properties, we show that there is no concentrated set of reals of size $\omega_2$ in the Miller model. The main result refutes a conjecture of Bartoszy\'{n}ski and Halbeisen. We also prove that there are no $\gamma$-set of reals of size $\omega_2$ in the Miller model.