Pontryagin Maximum Principle and Stokes Theorem

We present a new geometric unfolding of a prototype problem of optimal control theory, the Mayer problem. This approach is crucially based on the Stokes Theorem and yields to a necessary and sufficient condition that characterizes the optimal solutions, from which the classical Pontryagin Maximum Principle is derived in a new insightful way. It also suggests generalizations in diverse directions of such famous principle.Comment: 21 pages, 7 figures; we corrected a few minor misprints, added a couple of references and inserted a new section (Sect. 7); to appear in Journal of Geometry and Physic

On the localization principle for the automorphisms of pseudoellipsoids

We show that Alexander's extendibility theorem for a local automorphism of the unit ball is valid also for a local automorphism $f$ of a pseudoellipsoid \E^n_{(p_1, ..., p_{k})} \= \{z \in \C^n : \sum_{j= 1}^{n - k}|z_j|^2 + |z_{n-k+1}|^{2 p_1} + ... + |z_n|^{2 p_{k}} < 1 \}, provided that $f$ is defined on a region \U \subset \E^n_{(p)} such that: i) \partial \U \cap \partial \E^n_{(p)} contains an open set of strongly pseudoconvex points; ii) \U \cap \{z_i = 0 \} \neq \emptyset for any $n-k +1 \leq i \leq n$. By the counterexamples we exhibit, such hypotheses can be considered as optimal.Comment: 7 pages; to appear on Proceedings of AM

Total reality of conormal bundles of hypersurfaces in almost complex manifolds

A generalization to the almost complex setting of a well-known result by S. Webster is given. Namely, we prove that if $\Gamma$ is a strongly pseudoconvex hypersurface in an almost complex manifold $(M, J)$, then the conormal bundle of $\Gamma$ is a totally real submanifold of (T^*M, \J), where \J is the lifted almost complex structure on $T^*M$ defined by Ishihara and Yano.Comment: 8 page

Modular data and regularity of Monge-Amp\`ere exhaustions and of Kobayashi distance

Regularity properties of intrinsic objects for a large class of Stein Manifolds, namely of Monge-Amp\`ere exhaustions and Kobayashi distance, is interpreted in terms of modular data. The results lead to a construction of an infinite dimensional family of convex domains with squared Kobayashi distance of prescribed regularity properties. A new sharp refinement of Stoll's characterization of $\mathbb C^n$ is also given.Comment: 25 page