中科院数学与系统科学研究院
数学研究所
数理逻辑讨论班
报告人:Dr. Victor Torres Perez(TU Wien)
题 目:Diamonds, games and cardinal invariants
时 间:2018.10.11(星期四), 14:00--16:00
地 点:数学院南楼N820室
摘 要: On one hand, we prove that $\mathrm {WRP}$ and saturation of the ideal $\mathrm {NS}_{\omega_1}$ together imply $\Diamond\{a\in [\lambda]^{\omega_1}: \mathrm{cof}\left( \sup(a)\right)=\omega_1 \}$, for all regular $\lambda\geq \aleph_2$. On the other hand, in a joint work with Brendle and Hrusak, we consider a weak parametrized versions of the diamond principle which imply game versions of cardinal invariants $\mathfrak t$, $\mathfrak u$ and $\mathfrak a$. We show that the standard proof that parametrized diamond principles prove that the cardinal invariants are small actually show that their game counterparts are small. We show that $\mathfrak t<\mathfrak t_{game}$ and $\mathfrak u<\mathfrak u_{game}$ are both relatively consistent with the ZFC. The corresponding question for $\mathfrak a$ remains open.