arXiv subjects
Publications and source records attributed to Yinhe Peng.
We introduce a variant of the Kurepa family. We then use one such family to construct a ccc indestructible property associated with a complete coherent Suslin tree $S$. Moreover, in every ccc forcing extension that preserves Suslin of $S$, forcing with $S$ induces a strong negative partition relation.
We show that Martin's axiom for $ω_1$ dense sets is equivalent to its fragment asserting that every ccc poset has the Knaster property K$_3$. On the other hand, we show that the dimension 3 in K$_3$ is in some sense minimal.
Let $k$ be a commutative Noetherian ring, and $k[S]$ the polynomial ring whose indeterminates are parameterized by elements in a set $S$. We show that $k[S]$ is Noetherian up to highly homogenous actions of groups. In particular, there is a special linear order $\leqslant$ on infinite $S$ such that $k[S]$ is Noetherian up to actions of $\mathrm{Aut}(S, \leqslant)$, and the existence of such a linear order for every infinite set is equivalent to the axiom of choice. These Noetherian results are proved via a sheaf theoretic approach based on Artin's theorem, the work of Nagel-Römer, and a classification of highly homogenous groups by Cameron.
We introduce an iteration of forcing notions satisfying the countable chain condition with minimal damage to a strong coloring. Applying this method, we prove that Martin's axiom is strictly stronger than its restriction to forcing notions satisfying the countable chain condition in all finite powers. Our method shows also the finer distinction, that Martin's axiom is strictly stronger than its restriction to forcing notions whose squares satisfy the countable chain condition.
We construct in ZFC an L topological vector space -- a topological vector space that is an L space -- and an L field -- a topological field that is an L space. This generalizes results in [5] and [8].
We construct a model in which MA$_{ω_1}$(S)[S] holds and $\mathcal{K}_2$ fails. This shows that MA$_{ω_1}$(S)[S] does not imply $\mathcal{K}_2$ and answers an old question of Larson and Todorcevic in [3]. We also investigate different strong colorings in models of MA$_{ω_1}$(S)[S].
It is shown that the existence of an infinite set $A$ such that $A^2$ maps onto $2^A$ is consistent with $\mathsf{ZF}$.
It is proved in $\mathsf{ZF}$ (without the axiom of choice) that, for all infinite sets $M$, there are no surjections from $ω\times M$ onto $\mathscr{P}(M)$.
Strongly Turing determinacy, or $\mathrm{sTD}$, says that for any set $A$ of reals, if $\forall x\exists y\geq_T x (y\in A)$, then there is a pointed set $P\subseteq A$. We prove the following consequences of Turing determinacy ($\mathrm{TD}$) and $\mathrm{sTD}$: (1). $\mathrm{ZF+TD}$ implies weakly dependent choice ($\mathrm{wDC}$). (2). $\mathrm{ZF+sTD}$ implies that every set of reals is measurable and has Baire property. (3). $\mathrm{ZF+sTD}$ implies that every uncountable set of reals has a perfect subset. (4). $\mathrm{ZF+sTD}$ implies that for any set of reals $A$ and any $ε>0$, (a) there is a closed set $F\subseteq A$ so that $\mathrm{Dim_H}(F)\geq \mathrm{Dim_H}(A)-ε$. (b) there is a closed set $F\subseteq A$ so that $\mathrm{Dim_P}(F)\geq \mathrm{Dim_P}(A)-ε$.
Assuming $\mathrm{ZF}$, we prove that Turing determinacy ($\mathrm{TD}$) implies countable choice axiom for sets of reals ($\mathrm{CCR}$).