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Qing-Jin Cheng

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Preprint Sep 2026

Kazhdan's Property $(T)$ for Subspaces and Quotients of $L_p$-Spaces

We prove a uniform spectral-gap estimate at every even exponent for isometric representations on arbitrary closed subspaces of real $L_p$-spaces. As an application, this result, combined with the work of Bader, Furman, Gelander and Monod, gives an affirmative answer to their Question 4.1: Kazhdan's property $(T)$ impli...

Qing-Jin Cheng · 0 citations
Preprint Sep 2026

On Property (H) of c_0 and Lipschitz Problems of Gromov and Johnson

Let $X$ be a normed space and $S_X$ be the unit sphere of $X$. We say that $X$ has Property (H) if there exist two increasing sequences $V_j\subset X$ and $H_j\subset \ell_2$, $j=1,2,\ldots$, of finite dimensional subspaces such that $V=\bigcup_j V_j$ is dense in $X$, and there is a uniformly continuous mapping $\psi:S...

Li-Xin Cheng, Qing-Jin Cheng, Yue Wang · 2 citations · ⚡2
Preprint Sep 2026

The Optimal Scaling Parameter in Metric Cotype for Alexandrov Spaces of Nonnegative Curvature

We determine the optimal order of the scaling parameter in the metric cotype $2$ inequality for complete Alexandrov spaces of nonnegative curvature. It grows linearly with the dimension $n$ of the discrete torus. This answers Question 17 of Eskenazis, Mendel, and Naor. In their sign-vector normalization on $\bigl(\math...

Qing-Jin Cheng, Long-Fa Sun, Yi-Peng Zhang · 0 citations
Preprint Sep 2026

Sharp Metric Cotype Inequalities for $L_1$ via Nonlinear Cut Smoothing

For every $1\leq p<\infty$ and even integer $m\geq4$, we determine the optimal order of the $p$-moment torus inequality for $L_1$: it is $m^p n^{(1-p/2)_+}+n$, with comparison constants independent of $p,m,n$ after taking $p$-th roots. Consequently, for every $2\leq q<\infty$ and $1\leq p\leq q$, the corresponding metr...

Qing-Jin Cheng, Yue Wang, Bo Xiang · 2 citations

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