We study the dynamics of polynomial automorphisms of C^k. To an algebraically stable automorphism we associate positive closed currents which are invariant under f, considering f as a rational map on P^k. These currents give information on the dynamics and allow us to construct a canonical invariant measure which is shown to be mixing.

We investigate a problem of approximation of a large class of nonlinear expressions f(x, u, ∇u), including polyconvex functions. Here u: Ω→R^m, Ω⊂Rⁿ, is a mapping from the Sobolev space W^1,p. In particular, when p=n, we obtain the approximation by mappings which are continuous, differentiable a.e. and, if in addition n=m, satisfy the Luzin condition. From the point of view of applications such mappings are almost as good as Lipschitz mappings. As far as we know, for the nonlinear problems that we consider, no natural approximation results were known so far. The results about the approximation of f(x, u, ∇u) are consequences of the main result of the paper, Theorem 1.3, on a very strong approximation of Sobolev functions by locally weakly monotone functions.

We give interior estimates for first derivatives of solutions to a type of complex Monge-Ampère equations in convex domains. We also show global estimates for first derivatives of solutions in arbitrary domains. These global estimates are then used to show interior regularity of solutions to the complex Monge-Ampère equations in hyperconvex domains having a bounded exhaustion function which is globally Lipschitz. Finally we give examples of domains which have such an exhaustion function and domains which do not.

LetX be a complex manifold with finitely many ends such that each end is either q-concave or (n−q)-convex. If $q< \tfrac{1}{2}n$ , then we prove that H^pn−q(X) is Hausdorff for all p. This is not true in general if $q \geqslant \tfrac{1}{2}n$ (Rossi’s example with n=2 and q=1). If all ends are q-concave, then this is the classical Andreotti-Vesentini separation theorem (and holds also for $q \geqslant \tfrac{1}{2}n$ ). Moreover the result was already known in the case when the q-concave ends can be ‘filled in’ (again also for $q \geqslant \tfrac{1}{2}n$ ). To prove the result we first have to study Serre duality for the case of more general families of supports (instead of the family of all closed sets and the family of all compact sets) which is the main part of the paper. At the end we give an application to the extensibility of CR-forms of bidegree (p, q) from (n−q)-convex boundaries, $q< \tfrac{1}{2}n$ .

Letr, s ∈ [0, 1], and let X be a Banach space satisfying the M(r, s)-inequality, that is, $\parallel x^{***} \parallel \geqslant r\parallel \pi _X x^{***} \parallel + s\parallel x^{***} - \pi _X x^{***} \parallel for x^{***} \in X^{***} ,$ where π_X is the canonical projection from X^*** onto X^*. We show some examples of Banach spaces not containing c₀, having the point of continuity property and satisfying the above inequality for r not necessarily equal to one. On the other hand, we prove that a Banach space X satisfying the above inequality for s=1 admits an equivalent locally uniformly rotund norm whose dual norm is also locally uniformly rotund. If, in addition, X satisfies $\mathop {\lim \sup }\limits_\alpha \parallel u^* + sx_\alpha ^* \parallel \leqslant \mathop {\lim \sup }\limits_\alpha \parallel v^* + x_\alpha ^* \parallel $ whenever u^*, v^* ∈X^* with ‖u^*‖≤‖v^*‖ and (x ${}_{α}^{*}$ ) is a bounded weak^* null net in X^*, then X can be renormed to satisfy the, M(r, 1) and the M(1, s)-inequality such that X^* has the weak^* asymptotic-norming property I with respect to B_X.

We give a detailed description of nonconstant harmonic functions and their level sets on the Sierpiński gasket. We introduce a parameter, called eccentricity, which classifies these functions up to affine transformations h→ah+b. We describe three (presumably) distinct measures that describe how the eccentricities are distributed in the limit as we subdivide the gasket into smaller copies (cells) and restrict the harmonic function to the small cells. One measure simply counts the number of small cells with eccentricity in a specified range. One counts the contribution to the total energy coming from those cells. And one counts just those cells that intersect a fixed generic level set. The last measure yields a formula for the box dimension of a generic level set. All three measures are defined by invariance equations with respect to the same iterated function system, but with different weights. We also give a construction for a rectifiable curve containing a given level set. We exhibit examples where the curve has infinite winding number with respect to some points.

A Sobolev space in several variables in an L¹-type norm is not complemented in its second dual. Hence it is not isomorphic as a Banach space to any complemented subspace of a Banach lattice.

We study the Möbius invariant spaces Q_p and Q_{p, 0} of analytic functions. These scales of spaces include BMOA=Q₁, VMOA=Q_{1, 0} and the Dirichlet space=Q₀. Using the Bergman metric, we establish decomposition theorems for these spaces. We obtain also a fractional derivative characterization for both Q_p and Q_{p, 0}.