Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Shell structure in the lightest nuclei emerges from an unnaturally small
  expansion parameter in nuclear effective field theory   The strong interaction, i.e., quantum chromodynamics at the low energy
nuclear regime, is notoriously known to be challenging for predictive
modelling. Here, we use the simplest possible nuclear effective field theory
(EFT), and show that in the case of the magnetic structure of nuclear systems
with A=2 and A=3 nucleons it is highly precise, as well as predictive. The
theoretical framework is the pionless EFT, of point nucleons with contact
interactions, expanded consistently up to next-to-leading order (NLO) in
perturbation theory, i.e., including only eleven low-energy parameters, and
augmented by novel bayesian analysis of theoretical uncertainties. The theory
predicts accurately the shell structure reflected in the values of the magnetic
moments and reactions of these nuclei, within $\approx 1\%$ calculated
theoretical uncertainty. We show that this perfect prediction originates in
implicit a-posteriori properties of the calculation, particularly an
unexpectedly small expansion parameter, as well as vanishing contribution from
the two-body isoscalar current in contrast with the na\"ive dimensional
analysis of pionless EFT, indicating a misconception in identifying the
breakdown scale to the theory. We discuss possible origins and consequences of
these findings.

37
The categories of this paper are: supr-con
0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
2
The categories of this paper are: math
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org