Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Galactic-scale macro-engineering: Looking for signs of other intelligent
  species, as an exercise in hope for our own   If we consider Big History as simply 'our' example of the process of cosmic
evolution playing out, then we can seek to broaden our view of our possible
fate as a species by asking questions about what paths or trajectories other
species' own versions of Big History might take or have taken. This paper
explores the broad outlines of possible scenarios for the evolution of
long-lived intelligent engineering species---scenarios which might have been
part of another species' own Big History story, or which may yet lie ahead in
our own distant future. A sufficiently long-lived engineering-oriented species
may decide to undertake a program of macro-engineering projects that might
eventually lead to a re-engineered galaxy so altered that its artificiality may
be detectable from Earth. We consider activities that lead ultimately to a
galactic structure consisting of a central inner core surrounded by a more
distant ring of stars separated by a relatively sparser 'gap', where star
systems and stellar materials may have been removed, 'lifted' or turned into
Dyson Spheres. When one looks to the sky, one finds that such galaxies do
indeed exist---including the beautiful ringed galaxy known as 'Hoag's Object'
(PGC 54559) in the constellation Serpens. This leads us to pose the question:
Is Hoag's Object an example of galaxy-scale macro-engineering? And this
suggests a program of possible observational activities and theoretical
explorations, several of which are presented here, that could be carried out in
order to begin to investigate this beguiling question.

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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ph
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The categories of this paper are: cs
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The categories of this paper are: econ
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The categories of this paper are: supr-con
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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: plasm-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: patt-sol
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The categories of this paper are: ao-sci
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The categories of this paper are: q-fin
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The categories of this paper are: nlin
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The categories of this paper are: stat
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The categories of this paper are: gr-qc
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The categories of this paper are: funct-an