Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Classification theorems for operators preserving zeros in a strip   We characterize all linear operators which preserve spaces of entire
functions whose zeros lie in a closed strip. Necessary and sufficient
conditions are obtained for the related problem with real entire functions, and
some classical theorems of de Bruijn and P\'olya are extended. Specifically, we
reveal new differential operators which map real entire functions whose zeros
lie in a strip into real entire functions whose zeros lie in a narrower strip;
this is one of the properties that characterize a "strong universal factor" as
defined by de Bruijn. Using elementary methods, we prove a theorem of de Bruijn
and extend a theorem of de Bruijn and Ilieff which states a sufficient
condition for a function to have a Fourier transform with only real zeros.

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The categories of this paper are: q-fin
16
The categories of this paper are: stat
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
11
The categories of this paper are: hep-lat
29
The categories of this paper are: funct-an
10
The categories of this paper are: q-bio
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
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The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
3
The categories of this paper are: physics