activity
20182026
collaborators

6 papers

math.GT2026

Kwasik--Schultz manifolds are -compactifiable

Shijie Gu

Kwasik and Schultz constructed two-ended open -manifolds which satisfy the usual finiteness and stability conditions at infinity but do not admit arbitrarily small -neighborh…

math.MG2026

Busemann G-spaces with convex balls

Tadashi Fujioka, Shijie Gu

We prove that any Busemann G-space such that every sufficiently small metric ball is convex is a topological manifold. The key ingredient in the proof is Ivanov's Helly theorem. Th…

math.DG2026

Finsler structure of Busemann G-spaces

Tadashi Fujioka, Shijie Gu

We provide two sufficient conditions for a Busemann G-space to admit a differentiable DC atlas with a continuous Finsler metric, from the viewpoint of comparison geometry. These re…

math.GT2025

Nonembeddable contractible open manifolds arising from Whitehead doubling

Shijie Gu, Jian Wang, Yanqing Zou

We study a family of genus-one contractible open manifolds constructed by iterated Whitehead doubling from a nontrivial knot and an even half-twist . For each such pair, we…

math.DG2025

Topological regularity of Busemann spaces of nonpositive curvature

Tadashi Fujioka, Shijie Gu

We extend the topological results of Lytchak-Nagano and Lytchak-Nagano-Stadler for CAT(0) spaces to the setting of Busemann spaces of nonpositive curvature, i.e., BNPC spaces. We g…

math.GT2018

Characterization of pseudo-collarable manifolds with boundary

Shijie Gu

In this paper we obtain a complete characterization of pseudo-collarable -manifolds for . This extends earlier work by Guilbault and Tinsley to allow for manifolds with…