Having the H-space structure is not a generic property

In this note, we answer in negative a question posed by McGibbon about the generic property of H-space structure. In fact we verify the conjecture of Roitberg. Incidentally, the same example also answers in negative the open problem 10 in McGibbon

Equivariant Phantom maps

A successful generalization of phantom map theory to the equivariant case for all compact Lie groups is obtained in this paper. One of the key observations is the discovery of the fact that homotopy fiber of equivariant completion splits as product of equivariant Eilenberg-Maclane spaces which seems impossible at first sight by the example of Triantafillou

Rational homotopy theory and nonnegative curvature

In this note, we answer positively a question by Belegradek and Kapovitch about the relation between rational homotopy theory and a problem in Riemannian geometry which asks that total spaces of which vector bundles over compact nonnegative curved manifolds admit (complete) metrics with nonnegative curvature.Comment: 7 pages, talk to be given at SISTAG, National Univ. of Singapore, Jul.2-6, 200

Classification of the congruence classes of An5(n≥6)\mathbf{A}_n^5(n\geq 6) with 2-torsion free homology

In this paper, we classify the congruence classes of $\mathbf{F}^5_{n(2)}$-polyhedra, i.e. $(n-1)$-connected, at most $(n+5)$-dimensional polyhedra with 2-torsion free homology. The proof relies on the matrix problem technique which was developed in the classification of representations of algebras and applied to homotopy theory by Baues and Drozd.Comment: This article is accepted by SCIENCE CHINA Mathematics. arXiv admin note: text overlap with arXiv:1509.0793

The decomposability of smash product of A_n^2-complexes

In this paper, we determine the decomposability of smash product of two indecomposable A_n^2-complexes, i.e., (n-1)-connected finite CW-complexes with dimension at most n+2 (n\geq 3)

The stable homotopy classification of (n−1)(n-1)-connected (n+4)(n+4)-dimensional polyhedra with 2 torsion free homology

In this paper, we study the stable homotopy types of $\mathbf{F}^4_{n(2)}$-polyhedra, i.e., $(n-1)$-connected, at most $(n+4)$-dimensional polyhedra with 2-torsion free homologies. We are able to classify the indecomposable $\mathbf{F}^4_{n(2)}$-polyhedra. The proof relies on the matrix problem technique which was developed in the classification of representaions of algebras and applied to homotopy theory by Baues and Drozd

Toroidal orbifolds, gerbes and group cohomology

We compute the integral cohomology of certain semi-direct products arising from a linear G-action on the n-torus, where G is a finite group. The main application is the complete calculation of torsion gerbes for certain six dimensional examples arising from string theory

Secondary Brown-Kervaire Quadratic forms and π\pi-manifolds

In this paper we define a secondary Brown-Kervaire quadratic forms. Among the applications we obtain a complete classification of (n-2)-connected 2n-dimensional framed manifolds up to homeomorphism and homotopy equivalence, . In particular, we prove that the homotopy type of such manifolds determine their homeomorphism type

Mislin genus of maps

In this paper, we prove that the Mislin genus of a (co-)H-map between (co-)H-spaces under certain natural conditions is a finite abelian group which generalizes results in Zabrodsky, McGibbon and HurvitzComment: 27 page

Gerbes and twisted orbifold quantum cohomology

In this article, we construct an orbifold quantum cohomology twisted by a flat gerbe. Then we compute these invariants in the case of a smooth manifold and a discrete torsion on a global quotient orbifold.Comment: Amste