Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Krein extension of a differential operator of even order   We describe the Krein extension of minimal operator associated with the
expression A:=(-1)^n*d^(2n)/dx^(2n) on a finite interval (a,b) in terms of
boundary conditions. All non-negative extensions of the operator A as well as
extensions with a finite number of negative squares are described.

14
The categories of this paper are: math-ph
35
The categories of this paper are: mtrl-th
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
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The categories of this paper are: stat
23
The categories of this paper are: solv-int
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The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph