Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Escape and Trapping of Low-Frequency Gravitationally Lensed Rays by
  Compact Objects within Plasma   We consider the gravitational lensing of rays emitted by a compact object
(CO) within a distribution of plasma with power-law density $\propto r^{-h}$.
For the simplest case of a cloud of spherically symmetric cold non-magnetized
plasma, the diverging effect of the plasma and the converging effect of
gravitational lensing compete with one another. When $h<2$, the plasma effect
dominates over the vacuum Schwarzschild curvature, potentially shifting the
radius of the unstable circular photon orbit outside the surface of the CO.
When this occurs, we define two relatively narrow radio-frequency bands in
which plasma effects are particularly significant. Rays in the escape window
have $\omega_{0} < \omega \leq \omega_{+}$ and are free to propagate to
infinity from the CO surface. To a distant observer, the visible portion of the
CO surface appears to shrink as the observed frequency is reduced, and vanishes
entirely at $\omega_{0}$, in excess of the plasma frequency at the CO surface.
We define the anomalous propagation window for frequencies $\omega_{-}< \omega
\leq \omega_{0}$. Rays emitted from the CO surface within this frequency range
are dominated by optical effects from the plasma and curve back to the surface
of the CO, effectively cloaking the star from distant observers. We conclude
with a study of neutron star (NS) compactness ratios for a variety of nuclear
matter equations of state (EoS). For $h=1$, NSs generated from stiff EoS should
display significant frequency dependence in the EW, and lower values of $h$
with softer EoS can also show these effects.

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The categories of this paper are: hep-th
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
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The categories of this paper are: hep-ph
17
The categories of this paper are: q-fin
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The categories of this paper are: adap-org
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The categories of this paper are: chem-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: chao-dyn
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The categories of this paper are: acc-phys
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The categories of this paper are: dg-ga
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The categories of this paper are: q-bio
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The categories of this paper are: cmp-lg
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The categories of this paper are: supr-con
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The categories of this paper are: eess