I'm taking a first course on complex manifolds, and am trying to square what I hear with what I know of (real) differential geometry. Please forgive me if this question is misguided!
Here are two examples of ways of making vector bundles from codimension-one submanifolds.
- (The tensor powers of its associated line bundle) In a complex manifold $M$ with a codimension-1 complex submanifold $D$, take as an atlas a system $(U_alpha)$ of slice-coordinate charts for $V$, together with other charts $(V_beta)$ covering $Msetminus D$. For each $nin mathbb{Z}$, define a line bundle via the following transition functions: $phi_{beta_1beta_2}:V_{beta_1}cap V_{beta_2}to GL_1(mathbb{C})$ is uniformly =1; $phi_{alpha_1beta_2}:U_{alpha_1}cap V_{beta_2}to GL_1(mathbb{C})$ is $z_1^n$, and $phi_{alpha_1alpha_2}:U_{alpha_1}cap U_{alpha_2}to GL_1(mathbb{C})$ is $z_1^n/w_1^n$, where $z_1$ and $w_1$ are the coordinates whose vanishing determines $D$ on $U_{alpha_1}$ and $U_{alpha_2}$ respectively.
Comment: This also seems to work fine if we replace "complex" by "smooth (real)" throughout. However, the family of line bundles isn't so interesting: the even ones are all trivial; the odd ones are mutually isomorphic.
- (Vector bundles on spheres) For each homotopy class of maps $S^{n-1}to GL_k(mathbb{R})$, we can construct a vector bundle of rank $k$ on $S^n$, by using a representative of this class to define a transition function on the intersection of the "north" and "south" stereographic projection charts (which has $S^{n-1}$ as a retract).
I'd like to know: are these indeed analogous? Are they special cases of, say, a general method for constructing a smooth (respectively, complex) rank-$k$ vector bundle on a smooth (resp., complex) manifold out of a map from a codimension-one submanifold into $GL_k(mathbb{R})$ (resp., $GL_k(mathbb{C})$?
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