125,367 research outputs found
Some properties on -evaluation and its applications to -martingale decomposition
In this article, a sublinear expectation induced by -expectation is
introduced, which is called -evaluation for convenience. As an application,
we prove that any with some the
decomposition theorem holds and any integrable symmetric
-martingale can be represented as an It integral w.r.t
-Brownian motion. As a byproduct, we prove a regular property for
-martingale: Any -martingale has a quasi-continuous versionComment: 22 page
CMB Constraints on Principal Components of the Inflaton Potential
We place functional constraints on the shape of the inflaton potential from
the cosmic microwave background through a variant of the generalized slow roll
approximation that allows large amplitude, rapidly changing deviations from
scale-free conditions. Employing a principal component decomposition of the
source function G'~3(V'/V)^2 - 2V''/V and keeping only those measured to better
than 10% results in 5 nearly independent Gaussian constraints that maybe used
to test any single-field inflationary model where such deviations are expected.
The first component implies < 3% variations at the 100 Mpc scale. One component
shows a 95% CL preference for deviations around the 300 Mpc scale at the ~10%
level but the global significance is reduced considering the 5 components
examined. This deviation also requires a change in the cold dark matter density
which in a flat LCDM model is disfavored by current supernova and Hubble
constant data and can be tested with future polarization or high multipole
temperature data. Its impact resembles a local running of the tilt from
multipoles 30-800 but is only marginally consistent with a constant running
beyond this range. For this analysis, we have implemented a ~40x faster WMAP7
likelihood method which we have made publicly available.Comment: 12 pages, 14 figures, submitted to Phys.Rev.D. Optimized WMAP7
likelihood code and principal component functions of the GSR source function
available at http://background.uchicago.edu/wmap_fast
Two dimensional thermal and charge mapping of power thyristors
The two dimensional static and dynamic current density distributions within the junction of semiconductor power switching devices and in particular the thyristors were obtained. A method for mapping the thermal profile of the device junctions with fine resolution using an infrared beam and measuring the attenuation through the device as a function of temperature were developed. The results obtained are useful in the design and quality control of high power semiconductor switching devices
Model-Independent Reionization Observables in the CMB
We represent the reionization history of the universe as a free function in
redshift and study the potential for its extraction from CMB polarization
spectra. From a principal component analysis, we show that the ionization
history information is contained in 5 modes, resembling low-order Fourier modes
in redshift space. The amplitude of these modes represent a compact description
of the observable properties of reionization in the CMB, easily predicted given
a model for the ionization fraction. Measurement of these modes can ultimately
constrain the total optical depth, or equivalently the initial amplitude of
fluctuations to the 1% level regardless of the true model for reionization.Comment: 4 pages, 5 figures, submitted to PRD (rapid communications
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