Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Obstructing 4-torsion in the classical knot concordance group   We prove that if the order of the first homology of the 2-fold branched cover
of a knot K in the 3-sphere is given by pm where p is a prime congruent to 3
mod 4 and gcd(p,m) =1, then K is of infinite order in the knot concordance
group. This provides an obstruction to classical knots being of order 4. In
particular, there are 11 prime knots with 10 or fewer crossings that are of
order 4 in the algebraic concordance group; all are infinite order in
concordance. Another corollary states that any knot with Alexander polynomial
5t^2 - 11t + 5 is of infinite order in concordance; Levine proved that in
higher dimensions all such knots are of order 4.

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The categories of this paper are: q-fin
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
20
The categories of this paper are: acc-phys
27
The categories of this paper are: comp-gas
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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
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The categories of this paper are: alg-geom
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The categories of this paper are: adap-org
18
The categories of this paper are: econ