Assume $P$ is a family of primes, and let $()_P$ represent the $P$-localization functor. If $1\,{\to}\,N\stackrel{\iota}{\to} G\stackrel{\epsilon}{\to} Q\,{\to}\,1$ is an exact sequence of groups with $N$ finite, we prove that the sequence $N_P\stackrel{\iota_P}{\to} G_P\stackrel{\epsilon_P}{\to} Q_P\,{\to}\,1$ is exact. Moreover, we provide an explicit description of $\mbox{Ker}\ \iota_P$ when $Q$ belongs to a specific class of groups defined by a cohomological property. This class contains all nilpotent groups, all free groups and all $P$-local groups, as well as certain extensions formed from these three types of groups. In conclusion, we discuss the implications of our results for the study of finite-by-nilpotent groups.

It is proved that the exchange property, the Bass stable rank and the quasi-Bass property are all preserved under surjective inverse limits. This is then applied to multiplier rings by showing that these in many cases can be obtained as inverse limits.

We construct stably nontrivial vector bundles of dimension 5 and also stably nontrivial vector bundles of dimension 6 on real projective spaces of arbitrarily high dimensions. Consequently, we answer a problem posed by J. F. Adams.

Let $G_{\bb C}$ be the algebraic group over ${\bb C}$ corresponding a simply connected complex Lie group $G$. The algebraic cobordism $\Omega^*(G_{\bb C)$ defined by Levine and Morel is computed explicitly.

This paper presents some new results on algebraic K-theory with finite coefficients. The argument is based on a topological construction of a space $F_mK(R)$, for any ring $R$ and any integer $m\geq 2$, having the property that the ordinary homotopy theory of $F_mK(R)$ is isomorphic to the algebraic K-theory of $R$ with coefficients in $\bb {Z}/m$: $\pi_n(F_mK(R))\cong K_n(R;\bb {Z}/m)$ for $n\geq 1$. This space $F_mK(R)$ is called the $\mod m$ K-theory space of $R$. The paper is devoted to the investigation of several properties of the groups $K_n(R;\bb {Z}/m)$, for $n\in\bb {Z}$, and to some calculations of the integral homology of finite K-theory spaces.

We prove the following characterization of positive knots: a knot is positive if and only if it is homogeneous and strongly quasipositive.

Given a compact, connected, oriented 3-manifold $M$ with boundary, and epimorphism $\chi$ from $H_1M$ to a free abelian group $\Pi$, two invariants $\beta$, $\tau \in \bb {Z}\Pi$ are defined. If $M$ embeds in another such 3-manifold $N$ such that $\chi_N$ factors through $\chi$, then the product $\beta\tau$ divides $\Delta_0(H_1\tilde {N})$.

A theorem of D. Krebes concerning 4-tangles embedded in links arises as a special case. Algebraic and skein theoretic generalizations for $2n$-tangles provide invariants that persist in the corresponding invariants of links in which they embed. An example is given of a virtual 4-tangle for which Krebes's theorem does not hold.

Let $M$ be a closed oriented surface of negative Gaussian curvature and let $\Omega$ be a non-exact 2-form. Let $\lambda$ be a small positive real number. We show that the longitudinal KAM-cocycle of the magnetic flow given by $\la\,\Omega$ is a coboundary if and only if the Gaussian curvature is constant and $\Omega$ is a constant multiple of the area form.

We give a method to construct non-trivial $p$-harmonic morphisms via conformal change of the metric on the domain and/or the target manifold (Theorems 2.1, 2.5 and 2.8). As applications, we show the existence of higher dimensional harmonic spheres in general manifolds (Theorem 2.10) generalizing Sacks and Uhlenbeck's result on harmonic 2-spheres, prove some existence theorems for non-trivial $p$-harmonic morphisms between conformally flat spaces (Theorems 2.12, 3.1 and 3.2), give a method to construct minimal foliations via $p$-harmonic morphisms and show that many $\mathbf{R}^{m}$ with a conformally flat metric admit minimal foliations of codimension greater than two (Theorems 3.3, 3.4).

All $\cal {A}$-simple singularities of map-germs from $\bb {R}^n$ to $\bb {R}^p$, where $n\ge p$, of minimal corank (i.e. of corank $n-p+1$) have an M-deformation, that is a deformation in which the maximal numbers of isolated stable singular points are simultaneously present in the discriminant.

We modify arguments used in the study of Universal Taylor Series and extend them from simply connected domains to general domains in $\bb {C}$ to give a new simple and natural proof of the fact that all holomorphic functions are generically non extendable.

The structure of Dunford–Pettis sets, strong Dunford–Pettis sets and certain spaces of operators is studied in the context of the injective and projective tensor products of Banach spaces.

An analogue of the theory of integral closure and reductions is developed for a more general class of closures, called Nakayama closures. It is shown that tight closure is a Nakayama closure by proving a “Nakayama lemma for tight closure”. Then, after strengthening A. Vraciu's theory of *-independence and the special part of tight closure, it is shown that all minimal *-reductions of an ideal in an analytically irreducible excellent local ring of positive characteristic have the same minimal number of generators. This number is called the *-spread of the ideal, by analogy with the notion of analytic spread.