Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the origin of asymmetric fission of actinides   Nuclear fission of heavy (actinide) nuclei results predominantly in
asymmetric mass-splits. Without quantum shells, which can give extra binding
energy to these mass-asymmetric shapes, the nuclei would fission symmetrically.
The strongest shell effects are in spherical nuclei, so naturally the spherical
"doubly-magic" ${^{132}}$Sn nucleus (${Z=50}$ protons), was expected to play a
major role. However, a systematic study of fission has shown that the heavy
fragments are distributed around ${Z=52}$ to 56, indicating that ${^{132}}$Sn
is not the only driver. Reconciling the strong spherical shell effects at
${Z=50}$ with the different ${Z}$ values of fission fragments observed in
nature has been a longstanding puzzle. Here, we show that the final mass
asymmetry of the fragments is also determined by the extra stability of
octupole (pear-shaped) deformations which have been recently confirmed
experimentally around $^{144}$Ba (${Z=56}$), one of very few nuclei with
shell-stabilized octupole deformation. Using a modern quantum many-body model
of superfluid fission dynamics, we found that heavy fission fragments are
produced predominantly with ${52-56}$ protons, associated with significant
octupole deformation acquired on the way to fission. These octupole shapes
favouring asymmetric fission are induced by deformed shells at ${Z=52}$ and 56.
In contrast, spherical "magic" nuclei are very resistant to octupole
deformation, which hinders their production as fission fragments. These
findings may explain surprising observations of asymmetric fission of lighter
than lead nuclei.

10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
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The categories of this paper are: stat
29
The categories of this paper are: funct-an
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The categories of this paper are: q-fin
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The categories of this paper are: math
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The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
30
The categories of this paper are: q-alg