Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Machine-z: Rapid Machine Learned Redshift Indicator for Swift Gamma-ray
  Bursts   Studies of high-redshift gamma-ray bursts (GRBs) provide important
information about the early Universe such as the rates of stellar collapsars
and mergers, the metallicity content, constraints on the re-ionization period,
and probes of the Hubble expansion. Rapid selection of high-z candidates from
GRB samples reported in real time by dedicated space missions such as Swift is
the key to identifying the most distant bursts before the optical afterglow
becomes too dim to warrant a good spectrum. Here we introduce "machine-z", a
redshift prediction algorithm and a "high-z" classifier for Swift GRBs based on
machine learning. Our method relies exclusively on canonical data commonly
available within the first few hours after the GRB trigger. Using a sample of
284 bursts with measured redshifts, we trained a randomized ensemble of
decision trees (random forest) to perform both regression and classification.
Cross-validated performance studies show that the correlation coefficient
between machine-z predictions and the true redshift is nearly 0.6. At the same
time our high-z classifier can achieve 80% recall of true high-redshift bursts,
while incurring a false positive rate of 20%. With 40% false positive rate the
classifier can achieve ~100% recall. The most reliable selection of
high-redshift GRBs is obtained by combining predictions from both the high-z
classifier and the machine-z regressor.

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The categories of this paper are: cond-mat
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The categories of this paper are: stat
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The categories of this paper are: adap-org
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The categories of this paper are: econ
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The categories of this paper are: solv-int
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The categories of this paper are: comp-gas
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: alg-geom
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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: nucl-ex
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The categories of this paper are: math
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The categories of this paper are: q-bio
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The categories of this paper are: acc-phys