Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Algebraic properties of summation of exponential Taylor polynomials   Let $n\ge 1$ be an integer and $e_n(x)$ denote the truncated exponential
Taylor polynomial, i.e. $e_{n}(x)=\sum_{i=0}^n\frac{x^i}{i!}$. A well-known
theorem of Schur states that the Galois group of $e_n(x)$ over $\Q$ is the
alternating group $A_n$ if $n$ is divisible by 4 or the symmetric group $S_n$
otherwise. In this paper, we study algebraic properties of the summation of two
truncated exponential Taylor polynomials $\E_n(x):=e_n(x)+e_{n-1}(x)$. We show
that $\frac{x^n}{n!}+\sum_{i=0}^{n-1}c_i\frac{x^i}{i!}$ with all $c_i \ (0\le
i\le n-1)$ being integers is irreducible over $\Q$ if either $c_0=\pm 1$, or
$n$ is not a positive power of $2$ but $|c_0|$ is a positive power of 2. This
extends another theorem of Schur. We show also that $\E_n(x)$ is irreducible if
$n\not\in\{2,4\}$. Furthermore, we show that ${\rm Gal}_{\Q}(\E_n)$ contains
$A_{n}$ except for $n=4$, in which case, ${\rm Gal}_{\Q}(\E_4)=S_3$. Finally,
we show that the Galois group ${\rm Gal}_{\Q}(\E_n)$ is $S_n$ if $n\equiv 3
\pmod 4$, or if $n$ is even and $v_p(n!)$ is odd for a prime divisor of $n-1$,
or if $n\equiv 1\pmod 4$ and $n-2$ equals the product of an odd prime number
$p$ which is coprime to $\sum_{i=1}^{p-1}2^{p-1-i}i!$ and a positive integer
coprime to $p$.

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The categories of this paper are: q-fin
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The categories of this paper are: dg-ga
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The categories of this paper are: ao-sci
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The categories of this paper are: acc-phys
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The categories of this paper are: physics
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The categories of this paper are: solv-int
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The categories of this paper are: chao-dyn
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The categories of this paper are: nlin
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The categories of this paper are: atom-ph
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The categories of this paper are: funct-an
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: math-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: astro-ph