33,503 research outputs found
The PHOENIX Exoplanet Retrieval Algorithm and Using H Opacity as a Probe in Ultra-hot Jupiters
Atmospheric retrievals are now a standard tool to analyze observations of
exoplanet atmospheres. This data-driven approach quantitatively compares
atmospheric models to observations in order to estimate atmospheric properties
and their uncertainties. In this paper, we introduce a new retrieval package,
the PHOENIX Exoplanet Retrieval Analysis (PETRA). PETRA places the PHOENIX
atmosphere model in a retrieval framework, allowing us to combine the strengths
of a well-tested and widely-used atmosphere model with the advantages of
retrieval algorithms. We validate PETRA by retrieving on simulated data for
which the true atmospheric state is known. We also show that PETRA can
successfully reproduce results from previously published retrievals of WASP-43b
and HD 209458b. For the WASP-43b results, we show the effect that different
line lists and line profile treatments have on the retrieved atmospheric
properties. Lastly, we describe a novel technique for retrieving the
temperature structure and density in ultra-hot Jupiters using H
opacity, allowing us to probe atmospheres devoid of most molecular features
with JWST.Comment: 17 pages, 18 figures. Accepted for publication in A
Rank-normalization, folding, and localization: An improved for assessing convergence of MCMC
Markov chain Monte Carlo is a key computational tool in Bayesian statistics,
but it can be challenging to monitor the convergence of an iterative stochastic
algorithm. In this paper we show that the convergence diagnostic
of Gelman and Rubin (1992) has serious flaws. Traditional will
fail to correctly diagnose convergence failures when the chain has a heavy tail
or when the variance varies across the chains. In this paper we propose an
alternative rank-based diagnostic that fixes these problems. We also introduce
a collection of quantile-based local efficiency measures, along with a
practical approach for computing Monte Carlo error estimates for quantiles. We
suggest that common trace plots should be replaced with rank plots from
multiple chains. Finally, we give recommendations for how these methods should
be used in practice.Comment: Minor revision for improved clarit
Testing cosmic acceleration for parameterizations using measurements in galaxy clusters
In this paper we study the cosmic acceleration for five dynamical dark energy
models whose equation of state varies with redshift. The cosmological
parameters of these models are constrained by performing a MCMC analysis using
mainly gas mass fraction, , measurements in two samples of galaxy
clusters: one reported by Allen et al. (2004), which consists of points
spanning the redshift range , and the other by Hasselfield et al.
(2013) from the Atacama Cosmology Telescope survey, which consists of data
points in the redshift range . In addition, we
perform a joint analysis with the measurements of the Hubble parameter ,
baryon acoustic oscillations and the cosmic microwave background radiation from
WMAP and Planck measurements to estimate the equation of state parameters. We
obtained that both samples provide consistent constraints on the
cosmological parameters. We found that the data is consistent at the
confidence level with a cosmic slowing down of the acceleration at
late times for most of the parameterizations. The constraints of the joint
analysis using WMAP and Planck measurements show that this trend disappears. We
have confirmed that the probe provides competitive constraints on the
dark energy parameters when a is assumed.Comment: 21 pages, 8 Tables, 11 Figures, accepted for publication in MNRA
A Tutorial on Fisher Information
In many statistical applications that concern mathematical psychologists, the
concept of Fisher information plays an important role. In this tutorial we
clarify the concept of Fisher information as it manifests itself across three
different statistical paradigms. First, in the frequentist paradigm, Fisher
information is used to construct hypothesis tests and confidence intervals
using maximum likelihood estimators; second, in the Bayesian paradigm, Fisher
information is used to define a default prior; lastly, in the minimum
description length paradigm, Fisher information is used to measure model
complexity
Muon Simulations for Super-Kamiokande, KamLAND and CHOOZ
Muon backgrounds at Super-Kamiokande, KamLAND and CHOOZ are calculated using
MUSIC. A modified version of the Gaisser sea level muon distribution and a
well-tested Monte Carlo integration method are introduced. Average muon energy,
flux and rate are tabulated. Plots of average energy and angular distributions
are given. Implications on muon tracker design for future experiments are
discussed.Comment: Revtex4 33 pages, 16 figures and 4 table
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