r-critical points and Taylor expansion of the exponential map, for smooth immersions in Rk+n
[EN] Classically, the study of the contact with hyperplanes and hyperspheres has been realized by using the family of height and distance squared functions. On the first part of the thesis, we analyze the Taylor expansion of the exponential map up to order three of a submanifold $M$ immersed in $\r...
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| Tipo de recurso: | tesis doctoral |
| Fecha de publicación: | 2015 |
| País: | España |
| Institución: | Universitat Politècnica de València (UPV) |
| Repositorio: | RiuNet. Repositorio Institucional de la Universitat Politécnica de Valéncia |
| Idioma: | inglés |
| OAI Identifier: | oai:riunet.upv.es:10251/50935 |
| Acceso en línea: | https://riunet.upv.es/handle/10251/50935 |
| Access Level: | acceso abierto |
| Palabra clave: | Taylor expansion Gauss map Exponential map Asymptotic directions Strong principal directions Normal torsion MATEMATICA APLICADA |
| Sumario: | [EN] Classically, the study of the contact with hyperplanes and hyperspheres has been realized by using the family of height and distance squared functions. On the first part of the thesis, we analyze the Taylor expansion of the exponential map up to order three of a submanifold $M$ immersed in $\r n.$ Our main goal is to show its usefulness for the description of special contacts of the submanifolds with geometrical models. As we analyze the contacts of high order, the complexity of the calculations increases. In this work, through the Taylor expansion of the exponential map, we characterize the geometry of order higher than $3$ in terms of invariants of the immersion, so that the effective computations in specific cases become more affordable. It allows also to get new geometric insights. On the second part of the thesis, we introduce the concept of critical point of a smooth map between submanifolds. If we consider a differentiable $k$-dimensional manifold $M$ immersed in $\r{k+n},$ we know that its focal set can also be interpreted as the image of the critical points of the {\it normal map} $\nu(m,u): NM\to \r{k+n}$ defined by $\nu(m,u)=\pi_N(m,u)+ u,$ for $m\in M$ and $u\in N_mM,$ where $\pi_N:NM\to M$ denotes the normal bundle. In the same way, the parabolic set of a differential submanifold is given through the analysis of the singularities of the height functions over the submanifold. If we consider a differentiable $k$-dimensional manifold $M$ immersed in $\r{k+n},$ we know that its parabolic set can also be interpreted as the image of the critical points of the {\it generalized Gauss map} $\psi(m,u): NM\to \r{k+n}$ defined by $\psi(m,u)= u,$ for $u\in N_mM.$ Finally, we characterize the asymptotic directions as the tangent set of a $k$-dimensional manifold $M$ immersed in $\r{k+n}$ throughout the study of the singularities of the tangent map $\Omega(m,y): TM\to \r{k+n}$ defined by $\Omega(m,y)=\pi(m,y)+y,$ for $y\in T_mM,$ where $\pi:TM\to M$ denotes the tangent bundle. We describe first the focal set and its geometrical relation to the Veronese of curvature for $k$-dimensional immersions in $\r{k+n}.$ Then we define the $r$-critical points of a differential map $f:H \to K$ between two differential manifolds and characterize the $2$ and $3$-critical points of the normal map and generalized Gauss map. The number of these critical points at $m\in M$ may depend on the degeneration of the curvature ellipse and we calculate those numbers in the particular case that $M$ is an immersed surface in $\r{4}$ for the normal map and $\r{5}$ for the generalized Gauss map. |
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