Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On ill-posedness of nonparametric instrumental variable regression with
  convexity constraints   This note shows that adding monotonicity or convexity constraints on the
regression function does not restore well-posedness in nonparametric
instrumental variable regression. The minimum distance problem without
regularisation is still locally ill-posed.

7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
27
The categories of this paper are: comp-gas
3
The categories of this paper are: physics
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin