Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Unquantized anomalies in topological semimetals   Topological semimetals are a new class of metallic materials, which exist at
band fillings that ordinarily correspond to insulators or compensated
accidental semimetals with zero Luttinger volume. Their metallicity is a result
of nontrivial topology in momentum space and crystal symmetry, wherein
topological charges may be assigned to point band-touching nodes, preventing
gap opening, unless protecting crystal symmetries are violated. These
topological charges, however, are defined from noninteracting band eigenstates,
which raises the possibility that the physics of topological semimetals may be
modified qualitatively by electron-electron interactions. Here we ask the
following question: what makes the topological semimetals nontrivial beyond
band theory? Alternatively, can strong electron-electron interactions open a
gap in topological semimetals without breaking the protecting symmetries or
introducing topological order? We demonstrate that the answer is generally no,
and what prevents it is their topological response, or quantum anomalies. While
this is familiar in the case of magnetic Weyl semimetals, where the topological
response takes the form of an anomalous Hall effect, analogous responses in
other types of topological semimetals are more subtle and involve crystal
symmetry as well as electromagnetic gauge fields. Physically these responses
are detectable as fractional symmetry charges induced on certain gauge defects.
We discuss the cases of type-I Dirac semimetals and time-reversal invariant
Weyl semimetals in detail. For type-I Dirac semimetals, we also show that the
anomaly vanishes, in a nontrivial manner, if the momenta of the Dirac nodes
satisfy certain exceptional conditions.

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The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
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The categories of this paper are: ao-sci
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The categories of this paper are: stat
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The categories of this paper are: hep-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: math
3
The categories of this paper are: physics
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The categories of this paper are: hep-lat
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The categories of this paper are: supr-con
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The categories of this paper are: nlin
0
The categories of this paper are: hep-ph