Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An Exact SU(2) Symmetry and Persistent Spin Helix in a Spin-Orbit
  Coupled System   Spin-orbit coupled systems generally break the spin rotation symmetry.
However, for a model with equal Rashba and Dresselhauss coupling constant (the
ReD model), and for the $[110]$ Dresselhauss model, a new type of SU(2) spin
rotation symmetry is discovered. This symmetry is robust against
spin-independent disorder and interactions, and is generated by operators whose
wavevector depends on the coupling strength. It renders the spin lifetime
infinite at this wavevector, giving rise to a Persistent Spin Helix (PSH). We
obtain the spin fluctuation dynamics at, and away, from the symmetry point, and
suggest experiments to observe the PSH.

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The categories of this paper are: dg-ga
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The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc
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The categories of this paper are: math-ph
2
The categories of this paper are: math
18
The categories of this paper are: econ