Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spontaneously broken mass   The Galilei group involves mass as a central charge. We show that the
associated superselection rule is incompatible with the observed phenomenology
of superfluid helium 4: this is recovered only under the assumption that mass
is spontaneously broken. This remark is somewhat immaterial for the real world,
where the correct space-time symmetries are encoded by the Poincar\'e group,
which has no central charge. Yet it provides an explicit example of how
superselection rules can be experimentally tested. We elaborate on what
conditions must be met for our ideas to be generalizable to the relativistic
case of the integer/half-integer angular momentum superselection rule.

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The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat
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The categories of this paper are: alg-geom
3
The categories of this paper are: physics
8
The categories of this paper are: hep-ex
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The categories of this paper are: acc-phys
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The categories of this paper are: stat
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The categories of this paper are: nucl-ex
5
The categories of this paper are: gr-qc
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The categories of this paper are: cmp-lg
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The categories of this paper are: econ
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The categories of this paper are: funct-an
10
The categories of this paper are: q-bio
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The categories of this paper are: hep-lat