Skip to main content
2 of 3
edited tags
Mike Shulman
  • 66.8k
  • 7
  • 162
  • 368

Homotopy type of transversal families of submanifolds through deformation

Let $A,B \subset M$ be two transversal submanifolds of a compact manifold $M$. It seems rather intuitive that if $A$ and $B$ are deformed (say smoothly) in a way that they remain transversal to each other, the homotopy type of the intersection remains unchanged during the deformation.

I would like to know if there is a way to write such a homotopy in the following situations:

  1. $A = f^{-1}(0)$ is the zero level set of some smooth function $f : M \to \mathbb{R}$, and $B = B_s$ is a smooth family of submanifolds such that $A$ and $B_s$ are always transverse. Is it true that the homotopy type of $A \cap B_s$ is independent of $s$ ?
  2. $A_s := f_s^{-1}(0)$ is the zero set of a smooth function $f_s : M \to \mathbb{R}$, and the family $A_s$ is always transversal to a fixed submanifold $B$. Is it true that the homotopy type of $A_s \cap B$ is independent of $s$ ?

Any help will be appreciated. Thanks in advance.

BrianT
  • 1.2k
  • 8
  • 12