For natural numbers r and n ≥ 2 all natural operators T|Mfn T ∗(JrT ∗) transforming vector fields from n-manifolds M into 1-forms on JT ∗M = {j x(ω) | ω ∈ Ω(M), x ∈ M} are classified. A similar problem with fibered manifolds instead of manifolds is discussed.

We give a short review of Frobenius manifolds and algebraic integrability and study their intersection. The simplest case is the relation between the Frobenius manifold of simple singularities, which is almost dual to the integrable open Toda chain. New types of manifolds called extra special Kähler and special F -manifolds are introduced which capture the intersection.

Given two isospectral not isometric manifolds, we construct a new couple of such manifolds as the total spaces of two Riemannian submersions with totally geodesic fibers isometric to the given ones and of basis any other given manifold. By iteration, we obtain families of isospectral not isometric manifolds.

By studying modular invariance properties of some characteristic forms, we obtain twisted anomaly cancellation formulas. We apply these twisted cancellation formulas to study divisibilities on spin manifolds and congruences on spinc manifolds. Especially, we get twisted Rokhlin congruences for 8k + 4 dimensional spinc manifolds.

We investigate Chern number inequalities on Kähler-Einstein manifolds and their relation to uniformization. For Kähler-Einstein manifolds with c1 > 0, we prove certain Chern number inequalities in the toric case. For Kähler-Einstein manifolds with c1 < 0, we propose a series of Chern number inequalities, interpolating Yau’s and Miyaoka’s inequalities.

We introduced a class of conformally invariant Ehresmann connections so–called L-horizontal endomorphism in [7]. Using this class, we define conformally invariant manifolds: Wagner–type manifold and locally Minkowski–type manifold as special generalized Berwald manifolds. Then a generalization of Hashiguchi–Ichijyō’s Theorems to Wagner–type manifolds is presented. Mathematics Subject Classifica...

Small codimensional embedded manifolds defined by equations of small degree are Fano and covered by lines. They are complete intersections exactly when the variety of lines through a general point is so and has the right codimension. This allows us to prove the Hartshorne Conjecture for manifolds defined by quadratic equations and to obtain the list of such Hartshorne manifolds.

We consider variational inequality problems for set-valued vector fields on general Riemannian manifolds. The existence results of the solution, convexity of the solution set, and the convergence property of the proximal point algorithm for the variational inequality problems for set-valued mappings on Riemannian manifolds are established. Applications to convex optimization problems on Riemann...

The purpose of this note is to define a tri-moment map for certain manifolds with an Sp(1)-action. We show how this map can be used ro reduce such manifolds. The images of such maps for quaternionic flag manifolds, which are defined using the Dieudonné determinant, resemble the polytopes from the complex case.

For k 2, we exhibit complete k-curvature homogeneous neutral signature pseudoRiemannian manifolds which are not locally affine homogeneous (and hence not locally homogeneous). All the local scalar Weyl invariants of these manifolds vanish. These manifolds are Ricci flat, Osserman, and Ivanov–Petrova. Mathematics Subject Classification (2000): 53B20.