Displaying 3261 – 3280 of 8747

Showing per page

Invariant prolongation of BGG-operators in conformal geometry

Matthias Hammerl (2008)

Archivum Mathematicum

BGG-operators form sequences of invariant differential operators and the first of these is overdetermined. Interesting equations in conformal geometry described by these operators are those for Einstein scales, conformal Killing forms and conformal Killing tensors. We present a deformation procedure of the tractor connection which yields an invariant prolongation of the first operator. The explicit calculation is presented in the case of conformal Killing forms.

Invariant subspaces in higher order jet prolongations of a fibred manifold

Miroslav Doupovec, Alexandr Vondra (2000)

Czechoslovak Mathematical Journal

We present a generalization of the concept of semiholonomic jets within the framework of higher order prolongations of a fibred manifold. In this respect, a compilation of our 2-fibred manifold approach with the methods of natural operators theory is used.

Invariant torsion and G2-metrics

Diego Conti, Thomas Bruun Madsen (2015)

Complex Manifolds

We introduce and study a notion of invariant intrinsic torsion geometrywhich appears, for instance, in connection with the Bryant-Salamon metric on the spinor bundle over S3. This space is foliated by sixdimensional hypersurfaces, each of which carries a particular type of SO(3)-structure; the intrinsic torsion is invariant under SO(3). The last condition is sufficient to imply local homogeneity of such geometries, and this allows us to give a classification. We close the circle by showing that...

Invariant tracking

Philippe Martin, Pierre Rouchon, Joachim Rudolph (2004)

ESAIM: Control, Optimisation and Calculus of Variations

The problem of invariant output tracking is considered: given a control system admitting a symmetry group G , design a feedback such that the closed-loop system tracks a desired output reference and is invariant under the action of G . Invariant output errors are defined as a set of scalar invariants of G ; they are calculated with the Cartan moving frame method. It is shown that standard tracking methods based on input-output linearization can be applied to these invariant errors to yield the required...

Invariant tracking

Philippe Martin, Pierre Rouchon, Joachim Rudolph (2010)

ESAIM: Control, Optimisation and Calculus of Variations

The problem of invariant output tracking is considered: given a control system admitting a symmetry group G, design a feedback such that the closed-loop system tracks a desired output reference and is invariant under the action of G. Invariant output errors are defined as a set of scalar invariants of G; they are calculated with the Cartan moving frame method. It is shown that standard tracking methods based on input-output linearization can be applied to these invariant errors to yield the...

Invariant vector fields of Hamiltonians

Jacek Dębecki (1998)

Archivum Mathematicum

A complete classification of natural transformations of Hamiltonians into vector fields on symplectic manifolds is given herein.

Invariants and Bonnet-type theorem for surfaces in ℝ4

Georgi Ganchev, Velichka Milousheva (2010)

Open Mathematics

In the tangent plane at any point of a surface in the four-dimensional Euclidean space we consider an invariant linear map ofWeingarten-type and find a geometrically determined moving frame field. Writing derivative formulas of Frenet-type for this frame field, we obtain eight invariant functions. We prove a fundamental theorem of Bonnet-type, stating that these eight invariants under some natural conditions determine the surface up to a motion. We show that the basic geometric classes of surfaces...

Invariants and flow geometry

J. González-Dávila, L. Vanhecke (1999)

Colloquium Mathematicae

We continue the study of Riemannian manifolds (M,g) equipped with an isometric flow ξ generated by a unit Killing vector field ξ. We derive some new results for normal and contact flows and use invariants with respect to the group of ξ-preserving isometries to charaterize special (M,g, ξ ), in particular Einstein, η-Einstein, η-parallel and locally Killing-transversally symmetric spaces. Furthermore, we introduce curvature homogeneous flows and flow model spaces and derive an algebraic characterization...

Currently displaying 3261 – 3280 of 8747