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Let $S_0$ be a smooth compact $k$-dimensional manifold with boundary and $\mathcal{E}_{\rm p}(S_0, \mathbb{D}^n)$ be the space of smooth proper embeddings into the unit disk in $\mathbb{R}^n$ with the weak topology, as defined in Hirsch. Let $M \subseteq \operatorname{Int} \mathbb{D}^n$ be a smooth compact $n$-dimensional submanifold with boundary.

Let $\mathcal{C}_k(M)$ be the space of $k$-dimensional properly embedded submanifolds of $M$ with boundary, that is, $$ \mathcal{C}_k(M) = \coprod_{S} \mathcal{E}_{\rm p}(S, M)/\operatorname{Diff}(S) $$ where the union runs over each diffeomorphism type. Define $$\mathcal{E}^{M}_{\rm p}(S_0, \mathbb{D}^n) = \{\iota \colon S_0 \to \mathbb{D}^n \mid \iota \text{ is transverse to } \partial{M}\}.$$

If an embedding is transverse then $\iota({S}_0) \cap {M}$ is a submanifold of ${M}$ with boundary. Hence, there is an intersection map $\mathcal{E}^{{M}}_{\rm p}({S}_0, \mathbb{D}^n) \to \mathcal{C}_k({M})$.

Is $\mathcal{E}^{M}_{\rm p}({S}_0, \mathbb{D}^n)$ open, and is the intersection map continuous?

The first question might be answered with an argument like so: if $\iota_0$ is transverse, a nearby embedding $\iota$ will keep $\iota^{-1}(\partial M)$ close to $\iota_0^{-1}(\partial M)$, and the differential there will have not changed much, keeping transversality.

I believe the second question may be settled using an argument along the following lines. For every transverse embedding $\iota$, a basic open set $\mathcal{U}$ containing the intersection $N = \iota(S_0) \cap M$ consists of those submanifolds which are "close" to $N$. But the embeddings into $\mathbb{D}^n$ which are just as close to $\iota$ should map into $\mathcal{U}$.

However, it is not even clear how to show that a nearby embedding should have an intersection with $M$ that is even diffeomorphic to $N$, let alone close.

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    $\begingroup$ Yes, it's continuous. I suppose the way I'd formalize the argument is to put the perturbation (of an individual map or family) into a 1-parameter family, and form the "track" of that family. Then you observe the height function (mapping onto the track parameter) is a Morse function with no critical points. Then you could apply the Morse lemma to get your map between the two intersections. And later observe that map is "small" for small perturbations. That might not be an ideal argument but it's the first that comes to mind. $\endgroup$ Commented Nov 27 at 23:43
  • $\begingroup$ Thank you for your insight, Ryan. I was experimenting with constructing a smooth homotopy but the Morse lemma seems to save me work. I guess the first question can probably be answered using a 1-parameter family and an appropriate transversality theorem. I will try to write a solution along these lines. $\endgroup$ Commented Nov 28 at 0:33

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