Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Does tiny-scale atomic structure exist in the interstellar medium ?   We report on preliminary results from the recent multi-epoch neutral hydrogen
absorption measurements toward three pulsars, B0823+26, B1133+16 and B2016+28,
using the Arecibo telescope. We do not find significant variations in optical
depth profiles over periods of 0.3 and 9--10 yr, or on spatial scales of 10--20
and 70--85 AU. The large number of non detections of the tiny scale atomic
structure suggests that the AU-sized structure is not ubiquitous in the
interstellar medium and could be quite a rare phenomenon.

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The categories of this paper are: bayes-an
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The categories of this paper are: q-fin
21
The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys
22
The categories of this paper are: chao-dyn
11
The categories of this paper are: hep-lat
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The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
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The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph
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The categories of this paper are: dg-ga
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
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The categories of this paper are: econ
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The categories of this paper are: quant-ph
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The categories of this paper are: solv-int