3
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We know that the natural morphism $\pi:\mathfrak{M}_{\theta}(Q,\mathbf{v},\mathbf{w})\rightarrow \mathfrak{M}_0(Q,\mathbf{v},\mathbf{w})$ between a smooth and affine quiver variety is not necessarily surjective, so denote by $\mathfrak{M}_1$ its image.
E.g. picking the $A_1$ Dynkin quiver, standard stability condition $\theta>0,$ and dimension vectors $\mathbf{v}=4,\mathbf{w}=6,$ one gets the smooth quiver variety $\mathfrak{M}=T^*Gr(4,6)$ being cotangent bundle of Grassmanian, whereas $$\mathfrak{M}_1(A_1,4,6)=\overline{\mathcal{O}_{2211}}\subsetneq \mathfrak{M}_0(A_1,4,6)=\overline{\mathcal{O}_{222}},$$ are closures of nilpotent orbits in $\mathfrak{sl}_6.$ Also, using Nakajima reflection functors one can pass to the surjective setup. Namely, we have $\mathfrak{M}_{\theta>0}(A_1,4,6)\cong \mathfrak{M}_{\theta<0}(A_1,2,6),$ whereas both $\mathfrak{M}_0(A_1,2,6)$ and $\mathfrak{M}_1(A_1,2,6)$ are equal to $\overline{\mathcal{O}_{2211}}.$ The summary of these two examples is that:

  1. $\mathfrak{M}_1$ is a stratified closed subspace of $\mathfrak{M}_0$ = closed union of strata
  2. $\mathfrak{M}_1$ is an afine quiver variety
  3. Moreover, it is an affine quiver variety for the same quiver, though possibly with different dimension vectors
  4. Using Nakajima reflection functors, we can get to the setup where $\mathfrak{M}_1$ and $\mathfrak{M}_0$ coincide.

The question is, whether any of 1-4 holds in general, or at least for ADE Dynkin quiver varieties?

NB We assume that the complex moment parameter is equal to zero.

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