Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Class of Permutation Trinomials over Finite Fields   Let $q>2$ be a prime power and $f=-{\tt x}+t{\tt x}^q+{\tt x}^{2q-1}$, where
$t\in\Bbb F_q^*$. We prove that $f$ is a permutation polynomial of $\Bbb
F_{q^2}$ if and only if one of the following occurs: (i) $q$ is even and
$\text{Tr}_{q/2}(\frac 1t)=0$; (ii) $q\equiv 1\pmod 8$ and $t^2=-2$.

15
The categories of this paper are: nucl-ex
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The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
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The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
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The categories of this paper are: stat
18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
3
The categories of this paper are: physics
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The categories of this paper are: q-fin
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The categories of this paper are: astro-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg