Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Bulk topology of line-nodal structures protected by space group
  symmetries in class AI   We give an exhaustive characterization of the topology of band structures in
class AI, using nonsymmorphic space group 33 ($Pna2_1$) as a representative
example where a great variety of symmetry protected line-nodal structures can
be formed. We start with the topological classification of all line-nodal
structures given through the combinatorics of valence irreducible
representations (IRREPs) at a few high-symmetry points (HSPs) at a fixed
filling. We decompose the total topology of nodal valence band bundles through
the local topology of elementary (i.e. inseparable) nodal structures and the
global topology that constrains distinct elementary nodal elements over the
Brillouin zone (BZ). Generalizing from the cases of simple point nodes and
simple nodal lines (NLs), we argue that the local topology of every elementary
nodal structure is characterized by a set of poloidal-toroidal charges, one
monopole, and one thread charge (when threading the BZ torus), while the global
topology only allows pairs of nontrivial monopole and thread charges. We show
that all these charges are given in terms of symmetry protected topological
invariants, defined through quantized Wilson loop phases over symmetry
constrained momentum loops, which we derive entirely algebraically from the
valence IRREPs at the HSPs. In particular, we find highly connected line-nodal
structures, line-nodal monopole pairs, and line-nodal thread pairs, that are
all protected by the unitary crystalline symmetries only. Furthermore, we show
symmetry preserving topological Lifshitz transitions through which independent
NLs can be connected, disconnected, or linked. Our work constitutes a heuristic
approach to the systematic topological classification and characterization of
all momentum space line-nodal structures protected by space group symmetries in
class AI.

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The categories of this paper are: nucl-ex
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: q-fin
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The categories of this paper are: funct-an
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The categories of this paper are: solv-int
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-th
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The categories of this paper are: stat
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The categories of this paper are: q-alg
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The categories of this paper are: econ
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The categories of this paper are: bayes-an
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The categories of this paper are: cmp-lg
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The categories of this paper are: chem-ph
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The categories of this paper are: mtrl-th