The topology at infinity of Coxeter groups and buildings

The connectivity at infinity of a finitely generated Coxeter group W is completely determined by topological properties of its nerve L (a finite simplicial complex). For example, W is simply connected at infinity if and only if L and the subcomplexes (where ranges over all simplices in L) are simply connected. This characterization extends to locally finite buildings. Received: May 3, 2001     

A counterexample to the existence of a local plurisubharmonic peak function at infinity

We give an example of an unbounded pseudoconvex Reinhardt domain in , which is Kobayashi complete but admits no local plurisubharmonic peak function at infinity.

     

Bestvina's Normal Form Complex and the Homology of Garside Groups

A Garside group is a group admitting a finite lattice generating set . Using techniques developed by Bestvina for Artin groups of finite type, we construct K(π, 1)s for Garside groups. This construction shows that the (co)homology of any Garside group G is easily computed given the lattice , and there is a simple sufficient condition that implies G is a duality group. The universal covers of these K(π, 1)s enjoy Bestvina's weak nonpositive curvature condition. Under a certain tameness condition, this implies that every solvable subgroup of G is virtually Abelian.     

Multiple solutions for a degenerate elliptic equation involving sublinear terms at infinity

Some multiplicity results are presented for the eigenvalue problem

(Pλ,μ)     

Dominant and recessive solutions at infinity and genera of conjoined bases for discrete symplectic systems

In this paper we introduce the theory of dominant solutions at infinity for nonoscillatory discrete symplectic systems without any controllability assumption. Such solutions represent an opposite concept to recessive solutions at infinity, which were recently developed for such systems by the authors. Our main results include: (i) the existence of dominant solutions at infinity for all ranks in a given range depending on the order of abnormality of the system, (ii) construction of dominant solutions at infinity with eventually the same image, (iii) classification of dominant and recessive solutions at infinity with eventually the same image, (iv) limit characterization of recessive solutions at infinity in terms of dominant solutions at infinity and vice versa, and (v) Reid’s construction of the minimal recessive solution at infinity. These results are based on a new theory of genera of conjoined bases for symplectic systems developed for this purpose in this paper.     

Damped vibration problems with nonlinearities being sublinear at both zero and infinity

In this paper, we study a class of damped vibration problems with nonlinearities being sublinear at both zero and infinity, and we obtain infinitely many nontrivial periodic solutions by using a variant fountain theorem. To the best of our knowledge, there is no published result concerning this case by this method. Copyright © 2015 John Wiley & Sons, Ltd.     

Topology at infinity of polynominal mappings and Thom regularity condition

We consider polynomial mappings which have atypical fibres due to the asymptotic behavior at infinity. Fixing some proper extension of the polynomial mapping, we study the localizability at infinity of the variation of topology of fibres and the possibility of interpreting local results at infinity into global results. We prove local and global Bertini–Sard–Lefschetz type statements for noncompact spaces and nonproper mappings and we deduce results on the homotopy type or the connectivity of the fibres of polynomial mappings.     

Artin monoids inject in their groups

We prove that the natural homomorphism from an Artin monoid to its associated Artin group is always injective. Received: March 14, 2002     

On blow-up at space infinity for semilinear heat equations

A nonnegative blowing up solution of the semilinear heat equation ut=Δu+up with p>1 is considered when initial data u₀ satisfies

     

Relative Hyperbolicity and Artin Groups

Let G=⟨ a₁,&ldots; , a _n | a _i a _j a _i &ldots; = a_ja_ia_j,&ldots; ,i>j⟩ be an Artin group and let m _ij =m _ji be the length of each of the sides of the defining relation involving a _i and a _j . We show if all m_ij ⩾ 7 then G is relatively hyperbolic in the sense of Farb with respect to the collection of its two-generator subgroups a _i , a _j for which m_ij >&infty;.     

Monodromy at Infinity and the Weights of Cohomology

We show that for a polynomial map, the size of the Jordan blocks for the eigenvalue 1 of the monodromy at infinity is bounded by the multiplicity of the reduced divisor at infinity of a good compactification of a general fiber. The existence of such Jordan blocks is related to global invariant cycles of the graded pieces of the weight filtration. These imply some applications to period integrals. We also show that such a Jordan block of size greater than 1 for the graded pieces of the weight filtration is the restriction of a strictly larger Jordan block for the total cohomology group. If there are no singularities at infinity, we have a more precise statement on the monodromy.     

Fibers of Polynomial Mappings at Infinity and a Generalized Malgrange Condition

Let f be a complex polynomial mapping. We relate the behaviour of f at infinity to the characteristic cycle associated to the projective closures of fibres of f. We obtain a condition on the characteristic cycle which is equivalent to a condition on the asymptotic behaviour of some of the minors of the Jacobian matrix of f. This condition generalizes the condition in the hypersurface case known as Malgrange's condition. The relation between this condition and the behavior of the characteristic cycle is a partial generalization of Parusinski's result in the hypersurface case. We show that the new condition implies the C-triviality of f.     

一类五次多项式系统无穷远点等时中心条件与极限环分支

研究一类五次系统无穷远点的中心、拟等时中心条件与极限环分支问题.首先通过同胚变换将系统无穷远点转化成原点,然后求出该原点的前8个奇点量,从而导出无穷远点成为中心和最高阶细焦点的条件,在此基础上给出了五次多项式系统在无穷远点分支出8个极限环的实例.同时通过一种最新算法求出无穷远点为中心时的周期常数,得到了拟等时中心的必要条件,并利用一些有效途径一一证明了条件的充分性.     

Equivariant Poincaré duality for quantum group actions

We extend the notion of Poincaré duality in KK-theory to the setting of quantum group actions. An important ingredient in our approach is the replacement of ordinary tensor products by braided tensor products. Along the way we discuss general properties of equivariant KK-theory for locally compact quantum groups, including the construction of exterior products. As an example, we prove that the standard Podle? sphere is equivariantly Poincaré dual to itself.