Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Transient Observers and Variable Constants, or Repelling the Invasion of
  the Boltzmann's Brains   If the universe expands exponentially without end, ``ordinary observers''
like ourselves may be vastly outnumbered by ``Boltzmann's brains,'' transient
observers who briefly flicker into existence as a result of quantum or thermal
fluctuations. One might then wonder why we are so atypical. I show that tiny
changes in physics--for instance, extremely slow variations of fundamental
constants--can drastically change this result, and argue that one should be
wary of conclusions that rely on exact knowledge of the laws of physics in the
very distant future.

13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
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The categories of this paper are: eess
28
The categories of this paper are: alg-geom
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
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The categories of this paper are: nucl-ex
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-th
3
The categories of this paper are: physics
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The categories of this paper are: chao-dyn
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int