Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Comment on "Trouble with the Lorentz Law of Force: Incompatibility with
  Special Relativity and Momentum Conservation"   In a recent Letter [arXiv:1205.0096], Mansuripur considers a magnetic dipole
positioned at a fixed location from a point charge. Performing a Lorentz
transformation to a laboratory frame where the charge distribution moves he
finds that `a net torque acts on the dipole pair'. He then argues that `this
torque in the (lab) frame in the absence of a corresponding torque in the
(rest) frame is sufficient proof of the inadequacy of the Lorentz (force) law'.
  In this comment we demonstrate that the presence of a torque is not
incompatible with special relativity: it is required by the conservation laws
that apply to the total momentum of the system (including the particles). We
furthermore stress that classical electrodynamics needs a consistent dynamical
description of the particles that involves coupled equations for the
electromagnetic fields and the trajectories [M. Brachet and E. Tirapegui, Nuovo
Cimento Soc. Ital. Fis. A 47, 210 (1978)] and any conserved quantity will then
contain contributions from both the field and the particles.

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The categories of this paper are: plasm-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: cond-mat
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The categories of this paper are: quant-ph
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The categories of this paper are: funct-an
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The categories of this paper are: eess
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The categories of this paper are: q-bio
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The categories of this paper are: cs
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The categories of this paper are: solv-int
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The categories of this paper are: hep-ex
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The categories of this paper are: stat
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The categories of this paper are: patt-sol
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The categories of this paper are: q-alg
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The categories of this paper are: alg-geom
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The categories of this paper are: econ
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The categories of this paper are: nucl-th