Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Reconstruction of Static Black Hole Images Using Simple Geometric Forms   General Relativity predicts that the emission close to a black hole must be
lensed by its strong gravitational field, illuminating the last photon orbit.
This results in a dark circular area known as the black hole 'shadow'. The
Event Horizon Telescope (EHT) is a (sub)mm VLBI network capable of
Schwarzschild-radius resolution on Sagittarius A* (or Sgr A*), the 4 million
solar mass black hole at the Galactic Center. The goals of the Sgr A*
observations include resolving and measuring the details of its morphology.
However, EHT data are sparse in the visibility domain, complicating reliable
detailed image reconstruction. Therefore, direct pixel imaging should be
complemented by other approaches. Using simulated EHT data from a black hole
emission model we consider an approach to Sgr A* image reconstruction based on
a simple and computationally efficient analytical model that produces images
similar to the synthetic ones. The model consists of an eccentric ring with a
brightness gradient and a two-dimensional Gaussian. These elemental forms have
closed functional representations in the visibility domain, which lowers the
computational overhead of fitting the model to the EHT observations. For model
fitting we use a version of the Markov chain Monte-Carlo (MCMC) algorithm based
on the Metropolis-Hastings sampler with replica exchange. Over a series of
simulations we demonstrate that our model can be used for determining geometric
measures of a black hole, thus providing information on the shadow size,
linking General Relativity with accretion theory.

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The categories of this paper are: hep-ex
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The categories of this paper are: q-alg
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The categories of this paper are: math-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-th
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The categories of this paper are: bayes-an
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The categories of this paper are: cond-mat
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: mtrl-th
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The categories of this paper are: econ
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The categories of this paper are: dg-ga
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The categories of this paper are: acc-phys
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The categories of this paper are: chem-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: comp-gas