Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Energy-momentum tensor of a ferromagnet   The energy-momentum tensor of a ferromagnet derived according to the standard
prescription of Noether's theorem has a major flaw: the term originating from
the spin Berry phase is gauge-dependent. As a consequence, some physical
quantities computed from the tensor show unphysical behavior. For example, the
presence of a spin-polarized current does not affect the energy of the domain
wall in the commonly accepted gauge, which implies-incorrectly-the absence of
the adiabatic spin torque. In other gauges, the spin torque shows unphysical
glitches occurring when the plane of magnetization crosses the Dirac string
associated with a magnetic monopole in spin space. We derive a gauge-invariant
energy-momentum tensor that is free from these artifacts but requires the
addition of an extra spatial dimension, with the ferromagnet living on its
boundary. It can be obtained most directly from the Wess-Zumino action for
spins, which relies on the same extra dimension.

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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: funct-an
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The categories of this paper are: econ
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The categories of this paper are: math-ph
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The categories of this paper are: eess
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The categories of this paper are: chem-ph
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The categories of this paper are: q-fin
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The categories of this paper are: gr-qc
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The categories of this paper are: mtrl-th
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The categories of this paper are: ao-sci
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The categories of this paper are: cmp-lg
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The categories of this paper are: nlin
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The categories of this paper are: q-bio
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The categories of this paper are: alg-geom
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The categories of this paper are: chao-dyn