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Let $M,N$ be two Banach or Hilbert manifolds. Assume that $P\subset N$ is a smooth submanifold of $N$. We say that a smooth map $f:M \to N$ is Fredholm transversal to $P$ if for every $x\in M$ with $f(x)\in P$ the pair$(Df_x(T_x M), T_{f(x)} P)$ would be a Fredholm pair. (Recall that a Fredholm pair in a Banach or Hilbert space H is a pair of closed subspaces $(V,W)$ such that $V\cap W$ is a finite dimensional space and $V+W$ is a closed subspace of $H$ with finite codimension.

Is this terminology introduced in some reference? Let $H$ be a Hilbert space. Is there a submanifold $P\subset H$ for which there is no a surjective map $f:H \to H$ such that $f$ is Fredholm transverse to $P$? In particular does the unit sphere $P$ of $H$ admit a surjective Fredholm transversal map?

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    $\begingroup$ I think there is a typo in the definition of the pair. $\endgroup$
    – Thomas Rot
    Commented Apr 11, 2020 at 7:37
  • $\begingroup$ @ThomasRot I think it is identical to what the libked paper originally wrote. $\endgroup$ Commented Apr 11, 2020 at 8:01
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    $\begingroup$ Shouldn't $(Df_x(T_x M), T_{f(x)} N)$ be $(Df_x(T_x M), T_{f(x)} P)$? $\endgroup$
    – Thomas Rot
    Commented Apr 11, 2020 at 8:21
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    $\begingroup$ Otherwise the condition is that Df has finite rank $\endgroup$
    – Thomas Rot
    Commented Apr 11, 2020 at 8:47
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    $\begingroup$ You might be interested in this paper: arxiv.org/pdf/math/0309020.pdf $\endgroup$
    – Thomas Rot
    Commented Apr 12, 2020 at 13:19

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