5,565 research outputs found
Strategies For Covering the Uninsured: How California Policymakers Could Build on Lessons Learned at the Federal Level
Outlines possible health insurance coverage expansions in California that build on specific approaches from recent federal efforts
Stochastic determination of matrix determinants
Matrix determinants play an important role in data analysis, in particular
when Gaussian processes are involved. Due to currently exploding data volumes,
linear operations - matrices - acting on the data are often not accessible
directly but are only represented indirectly in form of a computer routine.
Such a routine implements the transformation a data vector undergoes under
matrix multiplication. While efficient probing routines to estimate a matrix's
diagonal or trace, based solely on such computationally affordable
matrix-vector multiplications, are well known and frequently used in signal
inference, there is no stochastic estimate for its determinant. We introduce a
probing method for the logarithm of a determinant of a linear operator. Our
method rests upon a reformulation of the log-determinant by an integral
representation and the transformation of the involved terms into stochastic
expressions. This stochastic determinant determination enables large-size
applications in Bayesian inference, in particular evidence calculations, model
comparison, and posterior determination.Comment: 8 pages, 5 figure
Early Implementation of the Health Coverage Tax Credit in Maryland, Michigan, and North Carolina: A Case Study Summary
Examines the effectiveness of HCTCs and assesses their prospects as a model for broader reforms. Proposes reforms to improve HCTCs' ability to help current target populations and aid policymakers in designing future health insurance tax credits
Diagnostics for insufficiencies of posterior calculations in Bayesian signal inference
We present an error-diagnostic validation method for posterior distributions
in Bayesian signal inference, an advancement of a previous work. It transfers
deviations from the correct posterior into characteristic deviations from a
uniform distribution of a quantity constructed for this purpose. We show that
this method is able to reveal and discriminate several kinds of numerical and
approximation errors, as well as their impact on the posterior distribution.
For this we present four typical analytical examples of posteriors with
incorrect variance, skewness, position of the maximum, or normalization. We
show further how this test can be applied to multidimensional signals
Phase diagram and phonon-induced backscattering in topological insulator nanowires
We present an effective low-energy theory of electron-phonon coupling effects for clean cylindrical topological insulator nanowires. Acoustic phonons are modelled by isotropic elastic continuum theory with stress-free boundary conditions. We take into account the deformation potential coupling between phonons and helical surface Dirac fermions, and also include electron-electron interactions within the bosonization approach. For half-integer values of the magnetic flux along the wire, the low-energy theory admits an exact solution since a topological protection mechanism then rules out phonon-induced -backscattering processes. We determine the zero-temperature phase diagram and identify a regime dominated by superconducting pairing of surface states. As example, we consider the phase diagram of HgTe nanowires. We also determine the phonon-induced electrical resistivity, where we find a quadratic dependence on the flux deviation from the nearest half-integer value
COBRA Subsidies for Laid-Off Workers: An Initial Report Card
Reviews the implementation of the government subsidy of COBRA health insurance premiums for laid-off workers in the 2009 stimulus package and its effects on COBRA enrollment and medical spending. Considers policy implications for access and affordability
Federal Subsidy for Laid-Off Workers' Health Insurance: A First Year's Report Card for the New COBRA Premium Assistance
Analyzes how the subsidy for laid-off workers' costs to continue their health coverage, included in the 2009 stimulus bill, affected enrollment. Considers determining factors, implications of health reform for extending the subsidy, and lessons learned
Fast and precise way to calculate the posterior for the local non-Gaussianity parameter from cosmic microwave background observations
We present an approximate calculation of the full Bayesian posterior
probability distribution for the local non-Gaussianity parameter
from observations of cosmic microwave background anisotropies
within the framework of information field theory. The approximation that we
introduce allows us to dispense with numerically expensive sampling techniques.
We use a novel posterior validation method (DIP test) in cosmology to test the
precision of our method. It transfers inaccuracies of the calculated posterior
into deviations from a uniform distribution for a specially constructed test
quantity. For this procedure we study toy cases that use one- and
two-dimensional flat skies, as well as the full spherical sky. We find that we
are able to calculate the posterior precisely under a flat-sky approximation,
albeit not in the spherical case. We argue that this is most likely due to an
insufficient precision of the used numerical implementation of the spherical
harmonic transform, which might affect other non-Gaussianity estimators as
well. Furthermore, we present how a nonlinear reconstruction of the primordial
gravitational potential on the full spherical sky can be obtained in principle.
Using the flat-sky approximation, we find deviations for the posterior of
from a Gaussian shape that become more significant for larger
values of the underlying true . We also perform a comparison to
the well-known estimator of Komatsu et al. [Astrophys. J. 634, 14 (2005)] and
finally derive the posterior for the local non-Gaussianity parameter
as an example of how to extend the introduced formalism to
higher orders of non-Gaussianity
Signal inference with unknown response: Calibration-uncertainty renormalized estimator
The calibration of a measurement device is crucial for every scientific
experiment, where a signal has to be inferred from data. We present CURE, the
calibration uncertainty renormalized estimator, to reconstruct a signal and
simultaneously the instrument's calibration from the same data without knowing
the exact calibration, but its covariance structure. The idea of CURE,
developed in the framework of information field theory, is starting with an
assumed calibration to successively include more and more portions of
calibration uncertainty into the signal inference equations and to absorb the
resulting corrections into renormalized signal (and calibration) solutions.
Thereby, the signal inference and calibration problem turns into solving a
single system of ordinary differential equations and can be identified with
common resummation techniques used in field theories. We verify CURE by
applying it to a simplistic toy example and compare it against existent
self-calibration schemes, Wiener filter solutions, and Markov Chain Monte Carlo
sampling. We conclude that the method is able to keep up in accuracy with the
best self-calibration methods and serves as a non-iterative alternative to it
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