Twistor spinors and solutions of the equation (E) on Riemannian manifolds
Twistor theory, self-duality and integrability
Twistor transforms of quaternionic functions and orthogonal complex structures
The theory of slice-regular functions of a quaternion variable is applied to the study of orthogonal complex structures on domains of . When is a symmetric slice domain, the twistor transform of such a function is a holomorphic curve in the Klein quadric. The case in which is the complement of a parabola is studied in detail and described by a rational quartic surface in the twistor space .
Twistors and gauge fields.
Two and three dimensional regions from homothetic motions.
Two applications of an integral formula
Two constructions with parabolic geometries
Two generalizations of Cheeger-Gromoll splitting theorem via Bakry-Emery Ricci curvature
In this paper, we prove two generalized versions of the Cheeger-Gromoll splitting theorem via the non-negativity of the Bakry-Émery Ricci curavture on complete Riemannian manifolds.
Two models of non-Euclidean spaces generated by associative algebras
Two new estimates for eigenvalues of Dirac operators
We establish lower and upper eigenvalue estimates for Dirac operators in different settings, a new Kirchberg type estimate for the first eigenvalue of the Dirac operator on a compact Kähler spin manifold in terms of the energy momentum tensor, and an upper bound for the smallest eigenvalues of the twisted Dirac operator on Legendrian submanifolds of Sasakian manifolds. The sharpness of those estimates is also discussed.
Two remarks about the connection of Jacobi and Neumann integrable systems.
Two special simply connected spaces of nonpositive curvature.
Two supergeometries from fourfold gradings of superalgebras
Two theorems on -Sasakian manifolds.
Two-dimensional curvature functionals with superquadratic growth
For two-dimensional, immersed closed surfaces , we study the curvature functionals and with integrands and , respectively. Here is the second fundamental form, is the mean curvature and we assume . Our main result asserts that critical points are smooth in both cases. We also prove a compactness theorem for -bounded sequences. In the case of this is just Langer’s theorem [16], while for we have to impose a bound for the Willmore energy strictly below as an additional condition....
Two-dimensional Helmholtz spaces.
Two-input control systems on the euclidean group SE (2)
Any two-input left-invariant control affine system of full rank, evolving on the Euclidean group SE (2), is (detached) feedback equivalent to one of three typical cases. In each case, we consider an optimal control problem which is then lifted, via the Pontryagin Maximum Principle, to a Hamiltonian system on the dual space 𝔰𝔢 (2)*. These reduced Hamilton − Poisson systems are the main topic of this paper. A qualitative analysis of each reduced system is performed. This analysis...
Two-jets of conformal fields along their zero sets
The connected components of the zero set of any conformal vector field v, in a pseudo-Riemannian manifold (M, g) of arbitrary signature, are of two types, which may be called ‘essential’ and ‘nonessential’. The former consist of points at which v is essential, that is, cannot be turned into a Killing field by a local conformal change of the metric. In a component of the latter type, points at which v is nonessential form a relatively-open dense subset that is at the same time a totally umbilical...
Two-parametric motions in
The paper deals with the local differential geometry of two-parametric motions in the Euclidean space. The first part of the paper contains contemporary formulation of classical results in this area together with the connection to the elliptical differential geometry. The remaining part contains applications. Necessary and sufficient conditions for splitting of a two-parametric motion into a product of two one-parametric motions, characterization of motions with constant invariants and some others....
Two-parametric systems of three-dimensional spaces in a unimodular six-dimensional affine space