Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the impact of magnetic-field models in galaxy clusters on constraints
  on axion-like particles from the lack of irregularities in high-energy
  spectra of astrophysical sources   Photons may convert to axion-like particles (ALPs) in external magnetic
fields. Under certain conditions, this effect should result in irregular
features in observed spectra of astrophysical sources. Lack of such
irregularities in particular spectra was used to constrain ALP parameters, with
two most popular sources being the radio galaxy NGC 1275 and the blazar PKS
2155-304. The effect and, consequently, the constraints, depend on the magnetic
fields through which the light from the source is propagated. Here, we revisit
ALP constraints from gamma-ray observations of NGC 1275 taking into account the
regular magnetic field of the X-ray cavity observed around this radio galaxy.
This field was not accounted for in previous studies, which assumed a model of
purely turbulent fields with coherence length much smaller than the cavity
size. For the purely regular field, ALP constraints are relaxed considerably,
compared to the purely turbulent one. While the actual magnetic field around a
source is an unknown sum of the turbulent and ordered components, the
difference in results gives an estimate of the theoretical uncertainty of the
study and calls for detailed measurements of magnetic fields around sources
used to constrain ALP properties in this approach.

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The categories of this paper are: nucl-th
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The categories of this paper are: quant-ph
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The categories of this paper are: adap-org
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-th
2
The categories of this paper are: math
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The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
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The categories of this paper are: solv-int
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The categories of this paper are: hep-ex
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The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
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The categories of this paper are: nucl-ex
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The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess