Author: Adam CoffmanPublisher: American Mathematical Soc.
ISBN: 0821846574
Category : Mathematics
Languages : en
Pages : 105
Book Description
"Volume 205, number 962 (first of 5 numbers)."
Unfolding CR Singularities
Author: Adam CoffmanPublisher: American Mathematical Soc.
ISBN: 0821846574
Category : Mathematics
Languages : en
Pages : 105
Book Description
"Volume 205, number 962 (first of 5 numbers)."
Metrics of Positive Scalar Curvature and Generalised Morse Functions, Part I
Author: Mark P. WalshPublisher: American Mathematical Soc.
ISBN: 082185304X
Category : Mathematics
Languages : en
Pages : 105
Book Description
It is well known that isotopic metrics of positive scalar curvature are concordant. Whether or not the converse holds is an open question, at least in dimensions greater than four. The author shows that for a particular type of concordance, constructed using the surgery techniques of Gromov and Lawson, this converse holds in the case of closed simply connected manifolds of dimension at least five.
Erdos Space and Homeomorphism Groups of Manifolds
Author: Jan Jakobus DijkstraPublisher: American Mathematical Soc.
ISBN: 0821846353
Category : Mathematics
Languages : en
Pages : 76
Book Description
Let M be either a topological manifold, a Hilbert cube manifold, or a Menger manifold and let D be an arbitrary countable dense subset of M. Consider the topological group H(M,D) which consists of all autohomeomorphisms of M that map D onto itself equipped with the compact-open topology. We present a complete solution to the topological classification problem for H(M,D) as follows. If M is a one-dimensional topological manifold, then we proved in an earlier paper that H(M,D) is homeomorphic to Qω, the countable power of the space of rational numbers. In all other cases we find in this paper that H(M,D) is homeomorphic to the famed Erdős space E E, which consists of the vectors in Hilbert space l2 with rational coordinates. We obtain the second result by developing topological characterizations of Erdős space.
Supported Blow-Up and Prescribed Scalar Curvature on $S^n$
Author: Man Chun LeungPublisher: American Mathematical Soc.
ISBN: 0821853376
Category : Mathematics
Languages : en
Pages : 112
Book Description
The author expounds the notion of supported blow-up and applies it to study the renowned Nirenberg/Kazdan-Warner problem on $S^n$. When $n \ge 5$ and under some mild conditions, he shows that blow-up at a point with positive definite Hessian has to be a supported isolated blow-up, which, when combined with a uniform volume bound, is a removable singularity. A new asymmetric condition is introduced to exclude single simple blow-up. These enable the author to obtain a general existence theorem for $n \ge 5$ with rather natural condition.
Affine Insertion and Pieri Rules for the Affine Grassmannian
Author: Thomas LamPublisher: American Mathematical Soc.
ISBN: 0821846582
Category : Mathematics
Languages : en
Pages : 103
Book Description
The authors study combinatorial aspects of the Schubert calculus of the affine Grassmannian ${\rm Gr}$ associated with $SL(n,\mathbb{C})$.Their main results are: Pieri rules for the Schubert bases of $H^*({\rm Gr})$ and $H_*({\rm Gr})$, which expresses the product of a special Schubert class and an arbitrary Schubert class in terms of Schubert classes. A new combinatorial definition for $k$-Schur functions, which represent the Schubert basis of $H_*({\rm Gr})$. A combinatorial interpretation of the pairing $H^*({\rm Gr})\times H_*({\rm Gr}) \rightarrow\mathbb Z$ induced by the cap product.
Quasi-Actions on Trees II: Finite Depth Bass-Serre Trees
Author: Lee MosherPublisher: American Mathematical Soc.
ISBN: 0821847120
Category : Mathematics
Languages : en
Pages : 118
Book Description
This paper addresses questions of quasi-isometric rigidity and classification for fundamental groups of finite graphs of groups, under the assumption that the Bass-Serre tree of the graph of groups has finite depth. The main example of a finite depth graph of groups is one whose vertex and edge groups are coarse Poincare duality groups. The main theorem says that, under certain hypotheses, if $\mathcal{G}$ is a finite graph of coarse Poincare duality groups, then any finitely generated group quasi-isometric to the fundamental group of $\mathcal{G}$ is also the fundamental group of a finite graph of coarse Poincare duality groups, and any quasi-isometry between two such groups must coarsely preserve the vertex and edge spaces of their Bass-Serre trees of spaces. Besides some simple normalization hypotheses, the main hypothesis is the ``crossing graph condition'', which is imposed on each vertex group $\mathcal{G}_v$ which is an $n$-dimensional coarse Poincare duality group for which every incident edge group has positive codimension: the crossing graph of $\mathcal{G}_v$ is a graph $\epsilon_v$ that describes the pattern in which the codimension 1 edge groups incident to $\mathcal{G}_v$ are crossed by other edge groups incident to $\mathcal{G}_v$, and the crossing graph condition requires that $\epsilon_v$ be connected or empty.
The Moment Maps in Diffeology
Author: Patrick Iglesias-ZemmourPublisher: American Mathematical Soc.
ISBN: 0821847090
Category : Mathematics
Languages : en
Pages : 85
Book Description
"This memoir presents a generalization of the moment maps to the category {Diffeology}. This construction applies to every smooth action of any diffeological group G preserving a closed 2-form w, defined on some diffeological space X. In particular, that reveals a universal construction, associated to the action of the whole group of automorphisms Diff (X, w). By considering directly the space of momenta of any diffeological group G, that is the space g* of left-invariant 1-forms on G, this construction avoids any reference to Lie algebra or any notion of vector fields, or does not involve any functional analysis. These constructions of the various moment maps are illustrated by many examples, some of them originals and others suggested by the mathematical literature."--Publisher's description.
On the Algebraic Foundations of Bounded Cohomology
Author: Theo BühlerPublisher: American Mathematical Soc.
ISBN: 0821853112
Category : Mathematics
Languages : en
Pages : 126
Book Description
It is a widespread opinion among experts that (continuous) bounded cohomology cannot be interpreted as a derived functor and that triangulated methods break down. The author proves that this is wrong. He uses the formalism of exact categories and their derived categories in order to construct a classical derived functor on the category of Banach $G$-modules with values in Waelbroeck's abelian category. This gives us an axiomatic characterization of this theory for free, and it is a simple matter to reconstruct the classical semi-normed cohomology spaces out of Waelbroeck's category. The author proves that the derived categories of right bounded and of left bounded complexes of Banach $G$-modules are equivalent to the derived category of two abelian categories (one for each boundedness condition), a consequence of the theory of abstract truncation and hearts of $t$-structures. Moreover, he proves that the derived categories of Banach $G$-modules can be constructed as the homotopy categories of model structures on the categories of chain complexes of Banach $G$-modules, thus proving that the theory fits into yet another standard framework of homological and homotopical algebra.
Topological Classification of Families of Diffeomorphisms Without Small Divisors
Author: Javier RibónPublisher: American Mathematical Soc.
ISBN: 0821847481
Category : Mathematics
Languages : en
Pages : 183
Book Description
The author gives a complete topological classification for germs of one-parameter families of one-dimensional complex analytic diffeomorphisms without small divisors. In the non-trivial cases the topological invariants are given by some functions attached to the fixed points set plus the analytic class of the element of the family corresponding to the special parameter. The proof is based on the structure of the limits of orbits when we approach the special parameter.
Operator Algebras for Multivariable Dynamics
Author: Kenneth R. DavidsonPublisher: American Mathematical Soc.
ISBN: 0821853023
Category : Mathematics
Languages : en
Pages : 68
Book Description
Let $X$ be a locally compact Hausdorff space with $n$ proper continuous self maps $\sigma_i:X \to X$ for $1 \le i \le n$. To this the authors associate two conjugacy operator algebras which emerge as the natural candidates for the universal algebra of the system, the tensor algebra $\mathcal{A}(X,\tau)$ and the semicrossed product $\mathrm{C}_0(X)\times_\tau\mathbb{F}_n^+$. They develop the necessary dilation theory for both models. In particular, they exhibit an explicit family of boundary representations which determine the C*-envelope of the tensor algebra.|Let $X$ be a locally compact Hausdorff space with $n$ proper continuous self maps $\sigma_i:X \to X$ for $1 \le i \le n$. To this the authors associate two conjugacy operator algebras which emerge as the natural candidates for the universal algebra of the system, the tensor algebra $\mathcal{A}(X,\tau)$ and the semicrossed product $\mathrm{C}_0(X)\times_\tau\mathbb{F}_n^+$. They develop the necessary dilation theory for both models. In particular, they exhibit an explicit family of boundary representations which determine the C*-envelope of the tensor algebra.