The notion of being totally umbilic is considered for non-degenerate and degenerate submanifolds of semi-Riemanian manifolds. After some remarks on the general case, timelike and lightlike totally umbilic submanifolds of Lorentzian manifolds are discussed, along with their physical interpretation in view of general relativity. In particular, the mathematical notion of totally umbilic submanifol...

Warped product CR-submanifolds in Kählerian manifolds were intensively studied only since 2001 after the impulse given by B.Y. Chen in [2], [3]. Immediately after, another line of research, similar to that concerning Sasakian geometry as the odd dimensional version of Kählerian geometry, was developed, namely warped product contact CR-submanifolds in Sasakian manifolds (cf. [6], [7]). In this n...

Recently, we researched certain twisted product CR-submanifolds in a Kaehler manifold and some inequalities of the second fundamental form of this submanifold ([11]). In this talk, we consider two kind twisted product CR-submanifolds in a locally conformal Kaehler manifold. In these submanifolds, we give a inequality of the second fundamental form (See Theorems 5.3 and 5.4) and consider the equ...

The main objective of this paper is to discuss a convexity theorem for a certain class of Riemannian manifolds, so-called isoparametric submanifolds, and how this relates to other convexity theorems. In the introduction we will present the convexity theorems. In Section 2 we will describe the geometry of isoparametric submanifolds and in Section 3 we will relate this to the geometries of the ot...

We study the problem of counting instantons with coassociative boundary condition in (almost) G2-manifolds. This is analog to the open GromovWitten theory for counting holomorphic curves with Lagrangian boundary condition in Calabi-Yau manifolds. We explain its relationship with the Seiberg-Witten invariants for coassociative submanifolds. Intersection theory of Lagrangian submanifolds is an es...

We show that the moduli spaces of associative submanifolds of a G 2 manifold (and Cayley submanifolds of a Spin(7) manifold) can be perturbed to smooth manifolds. By using connections as natural parameters and by constraining them with an additional equation and using Seiberg-Witten theory we can make them compact, and hence assign local invariants to these submanifolds. The local equations of ...

Abstract A relevant property of equifocal submanifolds is that their parallel sets are still immersed submanifolds, which makes them a natural generalization the so-called isoparametric submanifolds. In this paper, we prove regular fibers an analytic map π : M m+k → B k whenever endowed with complete Finsler metric and there restriction submersion for certain on image. addition, when provide si...

A calibration ¢ is a differential form on a Riemannian manifold with two additional properties. First, the form should be closed under exterior differentiation. Second, it should be less than or equal to the volume form on each oriented submanifold (of the same dimension as the degree of the form ¢). Each calibration ¢ determines a geometry of submanifolds, namely those oriented submanifolds fo...

A calibration ¢ is a differential form on a Riemannian manifold with two additional properties. First, the form should be closed under exterior differentiation. Second, it should be less than or equal to the volume form on each oriented submanifold (of the same dimension as the degree of the form ¢). Each calibration ¢ determines a geometry of submanifolds, namely those oriented submanifolds fo...

We prove that the associativity equations of two-dimensional topological quantum field theories are very natural reductions of the fundamental nonlinear equations of the theory of submanifolds in pseudo-Euclidean spaces and give a natural class of potential flat torsionless submanifolds. We show that all potential flat torsionless submanifolds in pseudo-Euclidean spaces bear natural structures ...