2,174 research outputs found
Tropical Pacific moisture variability
The research objectives are the following: (1) to describe synoptic scale variability of moisture over the tropical Pacific Ocean and the systems leading to this variability; (2) to implement satellite analysis procedures to accomplish (1); (3) to incorporate additional satellite information into operational analysis/forecast systems at NMC; and (4) to synthesize knowledge gained from satellite observations through diagnosis and numerical models. Significant accomplishments in FY 91/92 are presented and include the following: (1) satellite forecast applications; (2) satellite data analysis; and (3) tropical plume mechanisms
Spin transport in coupled spinor Bose gases
We report direct measurements of spin transport in a trapped, partially
condensed spinor Bose gas. Detailed analyses of spin flux in this
out-of-equilibrium quantum gas are performed by monitoring the flow of atoms in
different hyperfine spin states. The main mechanisms for motion in this system
are exchange scattering and potential energy inhomogeneity, which lead to spin
waves in the normal component and domain formation in the condensate. We find a
large discrepancy in domain formation timescales with those predicted by
potential-driven formation, indicating strong coupling of the condensate to the
normal component spin wave
Application of satellite data to tropic/subtropic moisture coupling
The objective is to utilize various satellite products from a number of satellites together with data observed from platforms available during the FGGE Special Observing Periods to diagnose synoptic scale events in date void regions. The focus is on episodes of northeastward traveling cloud bands which move out of the ITCZ over the eastern North Pacific Ocean. These events are called moisture bursts
Non-supersymmetric infrared perturbations to the warped deformed conifold
We analyze properties of non-supersymmetric isometry-preserving perturbations
to the infrared region of the warped deformed conifold, i.e. the Klebanov
Strassler solution. We discuss both perturbations that "squash" the geometry,
so that the internal space is no longer conformally Calabi-Yau, and
perturbations that do not squash the geometry. Among the perturbations that we
discuss is the solution that describes the linearized near-tip backreaction of
a smeared collection of anti-D3-branes positioned in the deep infrared. Such a
configuration is a candidate gravity dual of a non-supersymmetric state in a
large-rank cascading gauge theory. Although anti-D3-branes do not directly
couple to the 3-form flux, we argue that, due to the presence of the background
imaginary self-dual flux, anti-D3-branes in the Klebanov-Strassler geometry
necessarily produce singular non-imaginary self-dual flux. Moreover, since
conformally Calabi-Yau geometries cannot be supported by non-imaginary
self-dual flux, the anti-D3-branes squash the geometry as our explicit solution
shows. We also briefly discuss supersymmetry-breaking perturbations at large
radii and the effect of the non-supersymmetric perturbations on the gravitino
mass.Comment: 42 pages, references added, typos and minor errors corrected,
discussion of boundary conditions extended. Version to appear in NP
THE LINEAR REGRESSION MODEL WITH AUTOCORRELATED ERRORS: JUST SAY NO TO ERROR AUTOCORRELATION
This paper focuses on the practice of serial correlation correcting of the Linear Regression Model (LRM) by modeling the error. Simple Monte Carlo experiments are used to demonstrate the following points regarding this practice. First, the common factor restrictions implicitly imposed on the temporal structure of yt and xt appear to be completely unreasonable for any real world application. Second, when one compares the Autocorrelation-Corrected LRM (ACLRM) model estimates with estimates from the (unrestricted) Dynamic Linear Regression Model (DLRM) encompassing the ACLRM there is no significant gain in efficiency! Third, as expected, when the common factor restrictions do not hold the LRM model gives poor estimates of the true parameters and estimation of the ACLRM simply gives rise to different misleading results! On the other hand, estimates from the DLRM and the corresponding VAR model are very reliable. Fourth, the power of the usual Durbin Watson test (DW) of autocorrelation is much higher when the common factor restrictions do hold than when they do not. But, a more general test of autocorrelation is shown to perform almost as well as the DW when the common factor restrictions do hold and significantly better than the DW when the restrictions do not hold. Fifth, we demonstrate how simple it is to, at least, test the common factor restrictions imposed and we illustrate how powerful this test can be.Research Methods/ Statistical Methods,
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