Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Covariant Constitutive Relations and Relativistic Inhomogeneous Plasmas   The notion of a two-point susceptibility kernel used to describe linear
electromagnetic responses of dispersive continuous media in non-relativistic
phenomena is generalized to accommodate the constraints required of a causal
formulation in spacetimes with background gravitational fields. In particular
the concepts of spatial material inhomogeneity and temporal non-stationarity
are formulated within a fully covariant spacetime framework. This framework is
illustrated by re-casting the Maxwell-Vlasov equations for a collisionless
plasma in a form that exposes a 2-point electromagnetic susceptibility kernel
in spacetime. This permits the establishment of a perturbative scheme for
non-stationary inhomogeneous plasma configurations. Explicit formulae for the
perturbed kernel are derived in both the presence and absence of gravitation
using the general solution to the relativistic equations of motion of the
plasma constituents. In the absence of gravitation this permits an analysis of
collisionless damping in terms of a system of integral equations that reduce to
standard Landau damping of Langmuir modes when the perturbation refers to a
homogeneous stationary plasma configuration. It is concluded that constitutive
modelling in terms of a 2-point susceptibility kernel in a covariant spacetime
framework offers a natural extension of standard non-relativistic descriptions
of simple media and that its use for describing linear responses of more
general dispersive media has wide applicability in relativistic plasma
modelling.

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The categories of this paper are: gr-qc
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The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
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The categories of this paper are: astro-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: nlin
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The categories of this paper are: atom-ph
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The categories of this paper are: cs
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The categories of this paper are: nucl-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ex